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BUI V A N S A M - MAI S Y T U A N - I R A N K H A N H N G O C

H561D

U O N G DAN ON LUV6N

IHITOUNGHOC PHO IHONG
OUOC Gl

NHA X U A T B A N O A ! H O C S\J P H A M


BUI VAN SAM - MAI SY TUAN - TRAN KHANH NGOC

Hl/flNG DANONLUYEN
THITRUNG HOC PHO THONG QUOCGIA

MON SINH HOC

N H A XUAT BAN DAI HOC S U P H A M


UNIVERSITY

OF

EDUCATION

PUBLISHING

HOUSE

H U O N G DAN O N L U Y E N THI T R U N G H O C P H O T H O N G Q U O C GIA MON

SINH H O C

Bui Van Sam - Mai Sy Tuan - Tran Khanh Ngoc
Sacii duoc xuat ban phuc vu viec 6n luydn thi trung hoc pho thdng quoc gia t(i nam 2015
Ma so sach tieu chuan quoc te: ISBN 978-604-54-2246-5

Ban quyen xuat ban thuoc ve Nha xuat ban Dai hoc Su pham.
Mpi hinh thilc sao ch^p toan bo hay mot phan hoac cac hinh thitc ph^t hSnh
ma khong c6 su cho phep trU6c bSng van ban
cua Nha xuat ban Dai hoc Su pham deu la vi pham phap luat.

Chung tot ludn mong muon nhqn duoc nhOng y kien 66ng gdp cua quy vi doc gia
desdch ngay cang hoan thien han. Mpi gdp y ve sach, lien he ve ban thao va dich vu ban quyen
xin vui long gCri ve dia chi email: kehoach&nxbdhsp.edu.vn

Ma so: 01.02.177/900 - TK 2015


MUC

LUC

LOIGIOITHIEU

5

LOINOIDAU

6

Phan m o t : D I N H H U O N G C H U N G K I T H I T R U N G HQC PHO T H O N G QUOC GIA
M O N SINK HOC

7

Phan h a i : CAC C H U D E ON LUYEN

8

Chii de 1. Casaphdn
I.

hien tuong di truyen vd bien di

13
17

Co so tebdo

cua hien tuong di truyen vd bien di

Kien thuc c a b a n

I I . Bai tap m i n h hoa

26
31
34
34

I I . Bai tap m i n h hoa

44

I I I . Bai tap t u luyen

50

Chii de 4. Di truyen hoc qudn the.
I.
^'

21
21

I I I . Bai tap t u luyen
Chu de 3. Tinh quy ludt cua hien tuong di truyen vdbiendi
I . Kien thuc CO b a n

*

8

I I I . Bai tap t u l u y e n
I.

I

8

I I . Bai tap m i n h hoa
ChudeZ.
?

tiicua

T o m t a t kien thuc ca b a n

56

Kien thuc ca b a n

56

I I . Bai tap m i n h hoa

58

I I I . Bai tap t u luyen

61

Chii de 5. Ung dung di truyen hoc vd di truyen hoc nguoi
I.

Kien thuc ca b a n

65
65

I I . Bai tap m i n h hoa

69

I I I . Bai tap t u luyen

75

ChddeG.

Tien hod

80

I . Kien thiic ca ban
I I . Bai tap m i n h hoa

80
87

I I I . Bai tap t u luyen

88

Chd de 7. Sinh thai

I.

93

Kien thiic ca ban

93

I I . Bai tap m i n h hoa
I I I . Bai tap t u l u y e n

104
105

3


Phan ba:

M O T SO

DE T H I

THAM KHAO

DESOl

108

108

163

DE SOS

155

DE SO?

147

DE SO 6

139

DE SOS

131

D E S 6 4

123

DE SOS

116

DE 8 0 2

DAP A N VA

HUONG

D A N GIAI

171


Ldl GI6I THIEU

Thuc Men Quy6t dinh s6 3538/QD-BGDDT ngay 09/9/2014 ciia Bo tnrong Bo Gido due
va Dao tao phe duyet phuomg an thi tot nghiep trung hoc pho thong va tuyen sinh dai hoc,
cao dang tu nam 2015 (goi la ki thi trung hoe pho thong quoc gia), huong tdi vice thuc
hien doi mod chuong trinh va sach giao khoa, Nha xuat ban Dai hoe Su pham to chue
bien soan va phat hanh bo sach Hir&ng dan on luyen thi trung hoc pho thong quoc gia
gom 8 cuon, tuong ung vai 8 mon: Toan, Ngu van, Tilng Anh, Sinh hoc, Hoa hoc, Sinh
hoc, Lich su va Dia If.
Bo sach do cac tac gia la giang vien uy tin ciia Truong Dai hoc Su pham Ha Npi,
giao vien gioi a truong trung hoc pho thong va mot so can bo ciia cac ca quan chuyen
mon - nhung nguai c6 nhieu kinh nghiem tham gia cong tac tuyen sinh ciia Bg Giao due
va Dao tao - bien soan bam sat Chuang trinh giao due trung hoc pho thong, hudng tdi
doi mdi phuong phap day va hoc.
Cau true moi cuon sach gom ba phan:
Phan mot: Djnh huong chung ki thi trung hoc pho thong quoc gia (theo tung mon)
Phan hai: Cac chu d§/noi dung on luyen
Cae chu de/noi dung on luyen dugc bien soan doi mdi theo hudng danh gia nang lue,
bam sat quy dinh eua Bg Giao due va Dao tao ve cau true de thi, trong do eo phan tom
tat li thuyet, yeu cau ve bai tap/cau hoi van dung, cac bai tap/cau hoi mau va hudng dan
on luyen.
Phan ba: Mot so de thi tham khao

Cac de thi nay c6 dap an hoac hudng dan tra Idi. Hgc sinh nang cao dugc ki nang ren
luyen thuc hien trgn ven mot de thi trong thai gian quy djnh; mot mat luyen kha nang giai
bai tap, giai quyet van de, mat khac he thong hoa dugc cac kien thuc va ki nang can thiet
cho ki thi trung hgc pho thong quoc gia.
Cung vdi bg sach tren, Nha xuat ban Dai hgc Su pham tiep tue gidi thieu va phat hanh
bo sach Boi duong, on luyen thi trung hoc pho thong qu6c gia theo bo de gom 5 mon
(Toan, Ngu van, Tieng Anh, Sinh hgc, Hoa hgc) phuc vu hgc sinh on luyen thi trung hgc
pho thong quoc gia mot each hieu qua.
Dgi ngu giao vien pho thong c6 the su dung sach de hudng dan hgc sinh on luyen
kien thuc, ki nang theo hudng tiep can nang luc mot each c6 he thong nham dat hieu qua
cao nhat trong ki thi trung hgc pho thong quoc gia, bat dau thuc hien tu nam 2015.
Xin trdn trong gi&i thieu!
NHA XUAT BAN DAI HOC SlT PHAM


Ldl NOI DAU
Cuon sach nham dap ung nhu cau cua hoc sinh trong vice on luyen thi trung hoc
pho thong quoc gia mon Sinh hoc.
Ngi dung cuon sach gom ba phan, dugc cac tac gia bien soan theo huong doi mdi ve
hinh thuc va noi dung, dong thoi huong tdi nhiing tai lieu boi duong giao vien trong
nhung nam sau. Phdn mot la dinh huong chung ciia ki thi trung hoc pho thong quoc gia
mon Sinh hoc; Phdn hai la cac chii d l on luyen, Phdn ba gioi thieu mot so dk thi tham
khao CO huong dan giai.
Noi dung Phdn hai gom 7 chii de:
• Co so phan tii ciia hien tugng di truyen va bien di
• Co so te bao cua hien tugng di truyen va bien di
• Tinh quy luat ciia hien tugng di truyen va biSn dj
I • D i truyen hgc qukn the
• iTng dung di truydn hgc va di truySn hgc nguoi
• Tien hoa

• Sinh thai
Trong moi chii de, cac tac gia trinh bay thong nhat theo cac muc: Tom tat kien thuc
CO ban; Bai tap minh hoa; Mot so luu y; Mot so bai tap minh hoa; Bai tap tu luyen. Cuoi
chii de la dap an va huong din giai ph§n bai tap tu luyen.
Cuon sach con la tai lieu tham khao huu ich cho cac thay, c6 giao giup hgc sinh
on luyen hieu qua mon Sinh hgc trong ki thi trung hgc pho thong quoc gia.
Cac tac gia mong muon nhan dugc nhirng gop y ciia dgc gia va cac dong nghiep de
nang cao chat lugng cuon sach trong cac Ian xuat ban sau. Mgi y kien gop y cho cuon sach
xin gui ve dia chi:
Phong Bien tap, Nha xuat ban Dai hgc Su pham, Truong Dai hgc Su pham Ha Ngi So 136, Duong Xuan Thuy, Quan Cau Giay, Thanh pho Ha Ngi.
Cac tac gia


Phan mot
DjNH HadNG CHUNG Kl THI
TRUNG HOC PHO THONG QUOC GIA MON SINH HOC

Ngay 09/9/2014, Bo truong Bp Giao due va Dao tao da ban hanh QuySt dinh s6
3538/QD-BGDDT v^ viec phe duyet phifong an thi tot nghiep trung hoc pho thong va
tuyin sinh dqi hoc, cao dang tic nam 2015 (goi la ki thi trung hoc pho thong quoc gia),
trong do quy dinh thi sinh phai thi 4 mon toi thieu gom: 3 mon bat buoc la Toan, Ngii van,
Ngoai ngu va 1 mon tu chon trong cac mon Sinh hoc, Hoa hoc, Sinh hoc, Lich sii va Dia li.
Ngoai 4 mon thi noi tren, thi sinh c6 quydn dang ki thi them cac mon thi con lai ciia ki
thi de su dimg cho viec dang ki tuyen sinh dai hoc, cao dang theo yeu cau cua cac nganh
dao tao do tvmg truong dai hoc, cao dang quy dinh trong De an tuyen sinh cua truong do.
D§ thi trung hoc pho thong quoc gia nam 2015 mon Sinh hoc se c6 cau true tuomg tu
nhu d^ thi t6t nghiep trung hoc pho thong va de thi tuyen sinh vao dai hoc, cao dang
nam 2014. Noi dung de thi bam sat chuong trinh trung hoc pho thong, chii yeu la lop 12,
tang cucmg do phan hoa va c6 nhieu cau hoi mo. De thi c6 phan kiem tra kien thiic ca ban,
dung dk xet t6t nghiep; va phkn nang cao, dung de sang loc thi sinh trong tuyen sinh

vao cac truong dai hoc, cao dang.
ui-ixs.^n -^r.:
De thi dam bao ca 4 mure do nhgn biet, thong hieu, van dung, van dung cao, doi hoi
hoc sinh van dung kien thirc tSng hap, lien mon dS lam bai, giai quyet cac van de lien quan
d^n thirc tiin cuoc s6ng. Cong tac ra d8 thi tilp tuc dugc doi mai theo huong ddnh gid
ndng luc ngic&i hoc, tang dan cdc cau hoi a mite do van dung, cac cau hoi ma; noi dung
cau hoi chii trong hinh thanh pham chat, nang lire cua hoc sinh; de thi se tang dan yeu cau
van dung ki^n thuc tong hop, lien mon tu de den kho.
Be thi mon Sinh hoc d dang tAc nghiem khach quan vai thai gian lam bai la 90 phut.


Phan hai
C A C CHU D E ON L U Y E N
i

C H U D E 1 . C d S d P H A N TLT
C U A H I E N T a O N G Dl T R U Y E N VA B I E N D!

Vat chat di truyen va c d c h e phan tuf cua hien ti/dng di truyen, bien dj

1.

TOM TAT KIEN THL/C CO BAN

I.

- Vat chat di truyen a cip do phan tu la axit nucleic. C) virut, vat ch4t di truyin c6 thk
la A D N hoac ARN. O vi khuan (sinh vat nhan so) va sinh vat nhan thyc, vat chat
di truyen la ADN.
- Ca che phan tu cua hien tugng di truyen la qua trtnh nhan doi ADN, phien ma va

dich ma binh thuong.
^
- Ca che phan tu ciia hien tugmg biSn di la qua trinh nhan doi A D N , phien ma va
dich ma c6 xay ra sai sot.
2. G e n
- Gen la mot doan cua phan tu A D N mang thong tin ma hoa cho mot chu6i polipeptit
hay mot phan tu ARN.
- Thong tin di truyen trong gen dugc truyen tu te bao nay sang tS bao khac thong qua
qua trinh nhan doi ciia phan tu ADN trong qua trinh phan bao.
- Cau true chung ciia mot gen c§u true g6m 3 vung trinh tu nucleotit: viing dilu hoa,
viing ma hoa, viing ket thuc.
3.

Ma di truyen

- Gen dugc cau tao tu 4 loai nucleotit, con chuoi polipeptit dugc cau tao tu cac axit
amin. Thong tin ve trinh tu cac axit amin trong chuoi polipeptit dugc ma hoa trong gen
bang each cur 3 nucleotit lien nhau ma hoa cho 1 axit amin. Ba nucleotit l i l n nhau tren
mach goc cua gen ma hoa cho 1 axit amin dugc goi la bg ba ma hoa (triplet). Ba nucleotit
tren phan tu mARN bat doi bo sung vai triplet dugc goi la bo ba ma sao (codon). M6i
phan tu tARN c6 mot bg ba doi ma dac hieu dugc ggi la anticodon hit doi b6 sung vai
codon tren mARN.
- Cac dac diem cua ma di truyen: la ma bg ba; dugc dgc tu mot diem xac dinh theo
tung bg ba nucleotit va khong goi len nhau; c6 tinh ph6 bi§n; c6 tinh dac hieu va c6 tinh
thoai hoa.
4.

Qua trinh nhan doi ADN (tai bhn ADN, ttT s a o ADN)

- Tong hap cac mach dcm m&i: Do enzim A D N polimeraza chi di chuyen tren mach

khuon theo chieu 3' —> 5' nen cac mach mai luon dugc t6ng hgp theo chi^u 5' —> 3'.
Tren mach khuon c6 chieu 3' —> 5' thi mach mai dugc tong hgp lien tuc, con tren mach
khuon CO chieu 5'
3' thi mach mai dugc tong hgp ngat quang tao nen cac doan ngan


(doan Okazaki). Sau do cac doan Okazaki dugc noi lai voi nhau nha enzim noi (ligaza)
tao thanh soi hoan chinh.
- Mot so loai enzim tham gia vao qua trlnh nhan doi ADN:
+ Enzim thao xoin: giup cho 2 mach don ciia phan tu ADN tach nhau dan tao nen
chac chCr Y (chac tai ban) va de 16 2 mach khuon.
+ Enzim ADN polimeraza tong hop mach mai theo nguyen tac bo sung (A cap doi
voi T, G cap doi vdi X va ngugc lai).
+ Enzim n6i ligaza: n6i cac doan Okazaki voi nhau tao thanh mach hoan chinh.
- Nguyen tac nhdn doi:
+ Nguyen \kc khuon mlu (NTKM): M6i phan tu ADN con deu c6 hai mach don
trong do mot mach cu la tu ADN me (mach khuon), con mot mach mai dugc tong hgp tu
cac nucleotit tu do trong moi tnrcmg noi bao (con goi la nguyen tac ban bao toan).
+ Nguyen tic b6 sung (NTBS): Cac nucleotit tir do trong moi truong noi bao lien ket
voi cac nucleotit tren m6i mach don cua ADN theo nguyen tac bo sung (A cap doi bo
sung voi T, G cap doi b6 sung vdi X va ngugc lai).
t + Nguyen tac mot chieu: cac mach mai luon dugc tong hgp theo chieu 5' 3'.
—> Nha cac nguyen tac nhan doi ma tu mot phan tu ADN me tao thanh hai phan tii
ADN con giong nhau va giong phan tu ADN me.
- Qua trinh nhan doi ADN diln ra khSng binh thuang se phat sinh dot bien ggi la dot
bien gen. Dot bien gen la su bien doi trong cau true ciia gen. Bien doi lien quan den mot
cap nucleotit ggi la dot biSn diem. M6i \kn bien doi ve cau true ciia gen lai tao ra mot alen
mai khac vai alen ban dau. Alen mai quy dinh trang thai kieu hinh moi ciia tinh trang.
- Dot Men gen c6 the phdt sinh trong mot so truong hap sau day:
+ Sir kit cap khong diing trong qua trinh nhan doi ADN do bazo nita dang hiem hoac

do cac bazo nito bi ion hoa c6 the lam xuat hien dot bien gen dang thay the mot cap
nucleotit.
+ Tac dong ciia cac tac nhan gay dot bi8n: tac nhan 5BU c6 th§ gay dot biSn thay th8
cap A - T bang cap G - X; tac nhan acridin c6 the gay dot bien them hoac mat mot cap
nucleotit; tia UV c6 thS lam cho 2 baza timin tren cung mach lien ket vdi nhau cung dan
den phat sinh dot bien gen,...
- Dot biSn gen c6 thi gay hai, nhung ciing c6 the v6 hai hoac c6 Igi cho the dot bien.
Miic do gay hai ciia alen dot biSn gen phu thugc vao dieu kien moi truong va to hgp gen. A.
.r,., ,
V Phien ma
Dich ma „
ADN (gen)
> mARN
>• Protein

Tai ban

-r- L. *
• Tinh trang A

Sai sot
(dot bien gen)

ADN' (gen)

Pliien ma
Dich ma
• mARN' —
>• Protein'

> Tinh trang A'

{Lieu y: Trong so do tren, ki hieu A va A' nhSm bilu hien cac trang thai (kieu hinh) khac
nhau ciia cung mot tmh trang).

9


5. Qua trlnh phien ma
- Phien ma la qua trinh tong hop ARN tren khuon mau mach g6c cua gen.
- M o i gen c6 hai mach nucleotit nhung chi c6 1 mach dugc dung lam khuon (mach
goc) de tong hop ARN.
- Qua trinh phien ma dugc bat dau tir diem khai dau phien ma (nam o vung dieu hoa
cua gen) va ket thiic khi enzim ARN polimeraza gap tin hieu ket thiic (nSm d viing ket
thuc cua gen).
- Enzim ARN polimeraza tnrgt doc theo mach goc c6 chieu 3' —>• 5' de tong hop
phan tir mARN theo nguyen tac bo sung (A cap doi vai U, T cap doi voi A, G cap doi voi
X va ngugc lai) theo chieu 5' —> 3'.
- Nguyen tac phien ma: cung thirc hien theo cac nguyen t§c khuon mlu, b6 sung
va mot chieu (mot mach goc cua A D N lam khuon, cac nucleotit ISp rap theo nguyen tSc
bo sung, mach ARN luon dugc keo dai theo chieu 5' -> 3').
- Trong qua trinh phien ma cung c6 th^ xay ra cac sai sot nhu ghep nhim cac
nucleotit vai cac nucleotit tren mach goc khong dung theo nguyen tac bo sung, khi djch
ma se tao ra chuoi polipeptit bj bien doi, dan tdi c6 the lam xuat hien kieu hinh mai cua
tinh trang:
A n , M
/
, Phien ma
. r - , . ,
Dich ma

„
ADN (gen)
> mARN —
• Protein

• Tinh trang A

Tai ban
«r^i., ,
, Phien ma
ADN (gen)
¥ — > mARN

t

Dich ma
—
• Protein

^, ,
> Tinh trang A

Sai sot

6. Qua trinh djch ma
- Sff do khdi qudU

3'UAX

tARN:

5'AUG

mARN:

3'TAX

MachgSc:

XAA
GUU

XGG ... X X X
GXX ... GGG

XAA

XGG ... X X X

ATT5'
UAA3'
5'

Polipeptit: Axit amin ma dau - Vai - Ala - ... - Gly.
Protein:

- Vai - Ala - ... - Gly.

Sa do tren cho thay cac triplet bo sung vdi cac codon, cac codon lai bo sung vai cac
anticodon nen trinh tu cac triplet giong trinh tu cac anticodon (chi khac la T thay bang

U). Nha vay, thong tin di truyen tren mach goc cua gen dugc chuy^n thanh trinh tu cac
axit amin trong chuoi polipeptit. Do do, tARN con dugc ggi la "nguai" dich ma di truyen.
- Nguyen tac dich ma: cGng thuc hien theo cac nguyen tac khuon mau, b6 sung va
mot chieu (mARN lam khuon, su k i t cap giira cac codon tren mARN va cac anticodon
tren tARN theo nguyen tac bo sung, riboxom dich chuyen tren mARN theo chidu 5' -» 3').


- Viec dich ma c6 t h i sal sot nSu tARN khong lien kk dugc mot each chinh xac vai
dilng loai axit amin ma no can van chuyen hoac c6 the do ket cap nham giua codon va
anticodon (trong qua trinh dich ma) se tao thanh chu6i polipeptit bi bien doi.
ADN (gen) ""^'^^

mARN

Protein

> Ttnh trang A

Tai ban
, Phien ma
Dich ma „ ,
,,,
>• mARN
' ^
> Protein
ADN (gen)

^, ,
•TmhtrangA

Sal sot

7. Dieu hoa hoat dong cua gen
- Trong t^ bao c6 r§t nhiSu gen, nhung a tung thai diem chi c6 mot so gen hoat dong
(ma), con phan Ian cac gen a trang thai khong hoat dong (dong).
- Ca ch^ giup te bao c6 the nhan biet dugc thai diem nao thi cho gen hoat dong hay
khong hoat dong dugc goi la ca che dieu hoa hoat dong gen. Dieu hoa hoat dong gen
khong dung lai a viec "dong" hay "ma" gen ma con dieu khien lugng san pham cua gen
dugc tao ra nhieu hay ft phu hop vdi nhu cau cua te bao va ca the.
- Dieu hoa hoat dong gen dugc thuc hien a nhieu muc do khac nhau (phien ma, dich
ma, sau djch ma). 0 sinh vat nhan sa, qua trinh dieu hoa gen dugc thuc hien chu yeu a
miic do phien ma.
- Di^u hoa muc phien ma la di^u hoa lugng mARN dugc tong hgp trong te bao
(nhi^u hay it hoac khong tong hgp mARN), qua do dieu hoa lugng san pham cua gen.
Dieu hoa phien ma dugc minh hoa qua mo hinh \k ca che dieu hoa hoat dong gen cua
operon Lac do Jacop - Mono phat hien ra:
+ Khi moi truang khong c6 lactoza: Gen dieu hoa tong hgp protein uc che. Protein
uc che nay lien ket vai vung van hanh ciia gen ngan can qua trinh phien ma lam cho cac
gen cau true khong hoat dong (khong phien ma, khong djch ma).
+ Khi moi truang c6 lactoza: Mot so phan tu lactoza lien ket vai protein uc che lam
bien doi cau hinh khong gian ba chieu cua protein uc che dan den protein uc che khong
lien kk dugc vai viing van hanh cua gen, do vay ARN polimeraza c6 the lien ket vai
viing khai dong d l tien hanh phien ma va dich ma tao ra cac enzim phan giai duong
lactoza.
+ Khi duong lactoza trong moi truang te bao bi phan giai het thi protein uc che dugc
giai phong, lai lien kk vai vung van hanh va uc che hoat dong ciia cac gen cau true.

8. Tong ket ve cd sd phan tuf cua hien tiTdng di truyen va bien dj
- Cac qua trinh nhan doi, phien ma va dich ma deu dugc thuc hien theo cac nguyen tac
khuon mau, b6 sung va tong hgp cac chuoi theo mot chieu nhu dugc minh hoa trong

so do sau:


AON

5' ATA GXX GGG 3'

Tai ban
NTKM - NTBS

5' ATA G X X G G G 3 '
3 ' T A T X G G XXX 5'

3 ' T A T X G G X X X 5'
5 ' A T A GXX G G G 3 '

Phien mS
NTKM - NTBS
rtiARN

3 ' T A T X G G XXX 5'

5' AUA GXX GGG 3'
Djch ma
NTKM - NTBS

tARN

3' UAU

Chuoi polipeptit

XGG

XXX 5'

He - Ala - Gly

—>• Can ghi nha sa do va nhiimg luu y nay de lam cac dang bai tap ve nhan doi,
phien ma va djch ma.
- C a che phan tu ciia hien tugng di truyen dugc the hien a so d6 sau:
Co* che bieu hi^n thong tin di truyen trong dcri ca the

ADN
Cor che
truyen dgt
thong tin
di truyen
qua cac
thehf

_!!li^ARN

Pi^^^^ >

Protein

Tfnhtrang A

Bieu hoa ^ s . - - '

hoat d§ng
J
cua gen ^ ^ . ^

Tai ban

Phien
;n ma

^ADN

ARN

Dlqln ma
ma
Djch
— T
>

Protein

^

> Tinh trang A

- Ca che phan tu cua hien tugng bien di dugc the hien d sa do sau:
ADN ( g e n ) ^ l l ^ m A R N

Protein'" — * Tinh trang A'
Bien d| khong di truyen

(bien dj thirorng bien)

Sai sot

T

ADN ( g e n ) ' - ! ^ m A R N '

Djch ma

Protein"

-» Tinh trang A" .

Sai sot

ADN (gen) '-Ilif^mARN

Protein

-Tinh trgng A

) j ^ S a i s6t
Tai ban (dgt bien gen)
, PhienmS

ADN' (gen)

, DlchmS „ .

»-mARN'

,

» Protein'

„

Bien di di truyen
( b i e n d j d Q t bien)

,

* Tinh trang A'

12


Theo so d6 tren: Sai sot xay ra trong qua trinh truyen thong tin (qua trinh nhan doi A D N )
se tao ra dot bi€n gen {hiin

di d i truyen). Sai sot xay ra trong qua trinh bien hien gen

(phien ma, dich ma) hoac gap sir c6 trong qua trinh tuong tac v o i m o i truong se tao ra
thuong bi^n (biSn dj khong d i truyen, chi bieu hien trong d a i ca the).

II.

BAI TAP MINH HOA

A. MOTSOLJU Y
1- Gen

,r

Quy uac:

X ?: ^

A

+ So lugng nucleotit ciia gen:

N.

+ Chieu dai gen (mot mach):

L.

+ So lugng chu k i xoan ciia gen:

CK.

+ So lugng lien ket hoa tri giua cac nucleotit ciia gen: H T .
+ So lugng lien ket hidro cua gen: H .

1.1. Mgtsocong

thiic cabin

^

f=N-2(ADNmach,hSng)

„ = 2A + 3G

= N

'

' ""
^

^

( A D N mach vong)

( 3 ) % A + % G = 50%

(4)A +

G=y

=> Tir thiet lap cong thuc ve moi quan he giira N , L , C K va H T .

1.2. Quan he gi&a gen va hai mach dan
- Ve so lugng:
. A = T = ( A i + A2) = ( T i + T2) = ( A i + T i ) = (A2 + T2)

^

. G = X = ( G i + G2) = ( X i + X2) = (Gi + X , ) = (G2 + X2)

-Vitile%:
^

_

_ % A , + % A 2 _ %T^ + % T , _ % A , +

_ % A ; + %T^

_

"

_
%G,+%G._

2

_

_

_

2

2

_ % X , + % X , _ %Gi+%Xi _ % G ; + %X;

2

2

2

Trong do. A , T , G, X la so lugng hoac t i le % nucleotit m o i loai cua gen; A i , T i , A2,
T2,... la s6 lugng hoac t i le % nucleotit moi loai tren m o i mach dom cua gen.
Liru y:
Dang bai tap t i m s6 lugng nucleotit m 6 i loai cua gen la dang bai tap ca ban nhat v i
biet so lugng nucleotit m o i loai cua gen ta khong nhiing l a m dugc cac dang bai tap lien
quan dSn gen ma con su dung de giai cac dang bai tap ve nhan doi A D N , phien ma, dich
ma, dot bien gen.

13


2. Nhan doi ADN

Xet mpt gen nhan doi lien tiep k Ian (ban chat la te bao chua gen do nguyen phan
lien tiep k Ian):
- Tong so gen con dugc tao thanh = 2''.
- So gen con dugc cau tao hoan toan tu nucleotit ciia moi truong ngi bao = 2*" - 2.
- T o n g so nucleotit l§y tumoi truong npi bao = (2''- 1) X N.
- So lugng nucleotit moi loai liy tu moi truong ngi bao (mt):
' '
•A„, = T„« = ( 2 ' ' - l ) x A = ( 2 ' ' - l ) x T .

•
• G™ = X„ = (2"-1) X G = (2"-1) X X.
- So mach polinucleotit moi, lay nguyen lieu hoan toan tu moi truong ngi bao
_ 2*+!) _ 2
3.

Phien ma

- Quy uac: So lugng nucleotit moi loai cua phan tu mARN la mA, mU, mG, mX.
- Xet mot gen phien ma k Ian. Ta c6:
N
• So lugng nucleotit lay tir moi truong ngi bao - —xk.
• So lugng nucleotit moi loai lay tu moi truong ngi bao (mt):
Amt = Tgjc X k, Umt — Ag5c X k; Gmt = Xg6c X k; X^t = Gg^c x k.

- Moi quan he giura gen va mARN:
• Ve so lugng: A = T = mA + mU; G = X = mG + mX.
. v - * ' ! - u - , - c7 A oTT %mA + %mU
• Ve ti le phan tram: % A = %T =
; % G = %X
4.

%mG + %mX
.

Djch ma

- So lugmg lien ket hidro hinh thanh giua cudon va anticodon khi dich ma cho mot
chu6i polipeptit la: 2(mA + mU) + 3(mG + mX) - H a bg ba k^t thiic.
- Moi quan he giiia codon va anticodon: Theo NTBS va ngugc chieu. Codon ket

thuc khong ma hoa axit amin, do vay khong c6 anticodon tuong ling.
- Moi quan he givta anticodon va triplet (mach goc): cung chidu, chi thay U bSng T
hoac ngugc lai (thay T bSng U).
5. Dot bien gen

5.1. Quy Udc
n T
Cac bg ba c6 ma hoa axit amin dugc ggi la bg ba c6 nghia. Cac bg ba khong ma hoa
axit amin (bg ba ket thuc) dugc ggi la bg ba vo nghia. ,
. ; . •,
A

5.2. Mot so hau qui cua dot bien diem

Dot bien diem c6 the gay nen cac hau qua khac nhau trong qua trinh dich ma:
-Oboba ma ddu (thay ma mo dau bang ma khac): khong xay ra qua trinh dich ma.
-Oboba CO nghia:
W -— >

14


+ Co thk khong lam thay d6i s6 lirgng, thanh phan va trat ty sap xep cac axit amin
trong chu6i polipeptit dugc t6ng hgp (ma thoai hoa - thay cac bg ba cung ma hoa cho
mot loai axit amin).
+ Co the thay d6i mot loai axit amin trong chu6i polipeptit dugc tong hgp (thay bg ba
ma hoa axit amin nay bang bg ba ma hoa axit amin khac).
t
+ Co thk thay d6i mot loat cac axit amin ke tu diem bi dot bien mat hoac them
nucleotit (dot bien dich khung).

+ Co thi lam chu6i polipeptit bi ngan lai (thay bg ba c6 nghia bang bg ba ket thiic;
hoac lam ma ket thiic xuat hien sdm).
-Oboba ket thuc:
+ Thay ma kSt thuc nay bSng ma k^t thuc khac —»Khong anh huong den chuoi polipeptit.
+ Thay ma kit thiic bSng ma c6 nghia —> Co the lam chuoi polipeptit dai hon
binh thuong.
5.3. Tmh so gen dot bien
NSu mot gen c6 mot bazo nito dang hiem thi sau k Ian nhan doi, so gen dot bien
dugctao r a i a : 2''"'- 1.
5.4. Mot sodau hieu nhan biet dang dot bien
Co the can cu vao mot trong so cac dau hieu sau:
- Chieu dai cua gen (Lgen) truoc dot bien va Lgen sau dot bien.
- S6 lien ket hidro ciia gen (Hgen) truoc dot b i l n va Hgen sau dot bien.
- Tong s6 nucleotit cua gen truoc dot bien va sau dot bien.
- So lugng nucleotit moi loai ciia gen truoc dot bien va sau dot bien.
- S6 lugng, hoac thanh phSn, hoac trinh tu sap xep cac axit amin trong chuoi
polipeptit do gen truoc va sau dot bien tong hgp.
B. MOT S O BAI TAP MINH HOA
Cau 1: Khi phan tich mot axit nucleic nguoi ta thu dugc thanh phkn cua no c6 20% A,
20% G, 40% X va 20% T. Axit nucleic nay la
, .^-^
A. A D N CO c§u true dang sgi don.
B. A D N c6 c§u triic dang sgi kep.
- .
C. ARN CO c§u true dang sgi don.
D. ARN c6 cau true dang sgi kep.
Cau 2: Co mot trinh tu ARN [5' - AUG GGG UGX X A U UUU - 3'] ma hoi cho mot
doan polipeptit g6m 5 axit amin. Sir thay the nucleotit nao sau day dan den viec doan
polipeptit nay chi con lai 2 axit amin?
A. Thay th& A d bg ba nucleotit dau tien bang X .

B. Thay thS X d bg ba nucleotit thu ba bang A.
C. Thay th§ G a bg ba nucleotit dSu tien hang A.
. + A )xi! ~ I
D. Thay thI U d bg ba nucleotit thu ba bang X.
Cau 3: Mot phan tu mARN d E. coli c6 ti le % cac loai nucleotit la: U = 20%, X = 30%,
G = 20%. T i le % timg loai nucleotit trong vung ma hoa cvia gen da tong hgp nen phan tu
mARN tren la
A. G = X = 25%; A = T = 25%.
B. G = X = 30%; A = T = 20%.
C. G = X = 20%; A = T = 30%.
D . G = X = 10%; A = T = 40%.

15


C a u 4: A l e n B c6 chieu dai 153nm va c6 1169 lien k i t hidro b i dot bien thanh alen b.
M o t te bao chua cap gen Bb nguyen phan 2 Ian lien tiep da lay t u moi truong n p i bao
1083 nucleotit loai adenin va 1617 nucleotit loai guanin. Dang dot bien da xay ra v d i gen B la
A. thay the mot cap A - T bang mot cap G - X . B . mk mot cap A - T .
s ^:"i -*
C . thay t h i mot cap G - X b§ng mot cap A - T. D. m§t mot cap G - X .
C a u 5: Cho cac dot bien tren mach goc cua mot gen d sinh vat nhan so nhu sau:
1. thay T b k g A , bp ba 3 " n T 5 ' thanh 3 ' T T A 5 ' .
2. thay T hkng A , bp ba 3 ' T X T 5 ' thanh 3 ' A X T 5 ' .
< -i
3. thay T bang A , bp ba 3 ' T X T 5 ' thanh 3 ' T X A 5 ' .
4. thay T bSng A , bp ba 3 ' T T X 5 ' thanh 3 ' A T X 5 ' .
Trong cac bp ba sau dot bien a tren, c6 bao nhieu bp ba k h i phien ma se tao ra codon
kk thuc a m A R N ?
A. 1

B.2

C.3

D.4

H a d N G DAN GIAI
C a u 1: Chpn A . A x i t nucleic nay la A D N c6 cau true dang spi don, can cu vao 2 du kien:
- A x i t nucleic nay c6 4 loai baza nito A , T , G , X
la A D N .
- T i le ciia 4 loai baza nita A , T , G , X khong tuan theo nguyen tac bo sung ( A = T ; G = X )
la A D N spi don.
C a u 2: Chpn B , can c u vao 2 dix kien:
- Cac bp ba kk thuc g6m 3 bp ba: U A A , U A G , U G A
- K h i thay the X a bp ba nucleotit t h u ba bang A se lam bp ba U G X b i l n thanh bp ba
U G A la mot trong 3 bp ba ket thuc —• lam dung qua trinh t6ng hap chudi polipeptit, dan tod
doan polipeptit nay chi con lai 2 axit amin (cua bp ba t h u nhSt va t h u hai).
C a u 3: Chpn A .
- T u ti le cac loai nucleotit da cho ciia doan m A R N tinh dupe t i le nucleotit loai A = 30%.
^' - A p dung quan he gen va m A R N , ta c6: % A = % T = 2 5 % ; % G = % X = 25%.
C a u 4: Chpn A .
- T i n h so nucleotit tung loai ciia alen B :
+ Tdng s6 nucleotit cua alen B la

x 2 = 900 nucleotit.
3,4

+ So lupTig nucleotit tung loai cua alen B la:
2A + 3 G = 1169 va 2 A + 2G = 900 =^ A B = T B = 181 va G B =

- T i n h so nucleotit tung loai ciia alen b:
( 2 ^ - l ) x ( A 3 + A J - 1083 ^ A , = T , = 180
}
(2^-

1)X(G3+ G J

= 1617

G, = X,=

XB

= 269.

(1)
^
(2)

270

T u (1) va (2) => A l e n b c6 s6 nucleotit loai A giam 1 va loai G tang 1 => Dang dot
bien xay ra v a i alen B la thay the 1 cap A - T bang 1 cap G - X .
C a u 5: Chpn B . M a c h ma g6c c6 bp ba 3 ' A X T 5 ' va 3 ' A T X 5 ' k h i phien ma se tao ra
bp ba 5 ' U G A 3 ' va bp ba 5 ' U A G 3 ' la cac bp ba kk thiic tren m A R N .


III. BAI T A P TLT L U Y E N

Cau 1: Tren mach 1 ciia gen c6 nucleotit loai A bang 150, loai T bang 450; tren mach 2

cua gen nay CO nucleotit loai G bang 300, loai X b^ng 600.
1. Tinh ti le % nucleotit moi loai tren moi mach don ciia gen.
2. Tinh ti le % nucleotit moi loai cua gen.
Cau 2: Mot gen c6 2880 lien ket hidro va c6 nucleotit loai A nhieu han nucleotit loai
khac la 10% tong so nucleotit cua gen. Gen tren bi dot bien thay the mot cap nucleStit.
1. Neu so lugng lien ket hidro cua gen sau dot bien khong doi thi dot bien xay ra nhu
the nao?
2. Neu so lugng lien ket hidro ciia gen sau dot bien thay doi thi so lugng nucleotit
moi loai ciia gen la bao nhieu?
Cau 3: Alen A bj dot bien thanh alen a. Phan tich chuoi polipeptit do alen a tong hgp so
vai chuoi polipeptit do alen A tong hgp thi hoan toan giong nhau ve so lugng, thanh phan
va trinh tu sap xep cac axit amin. Dang dot bien nao da xay ra vdi alen A?
Cau 4: Tren phan tu mARN c6 s6 nucleotit cac loai nhu sau: 450A, 150U, 600G, 300X.
Phan tu mARN dugc djch ma binh thucmg tao thanh 4 chu6i polipeptit. Xac djnh so
lugng lien ket hidro dugc hinh thanh giiia anticodon va codon, biet bg ba ket thiic tren
mARN la UAG.
Cau 5: Trong ca che dieu hoa boat dgng ciia operon Lac, sir kien nao sau day dien ra ca
khi moi truang c6 lactoza va khi moi truang khong c6 lactoza?
A. ARN polimeraza lien ket voi vung khai dgng cua operon Lac va ti^n hanh phien ma.
B. Mot so phan tu lactoza lien ket vai protein uc che.
C. Gen dieu hoa R tong hgp protein uc che.
D. Cac gen cau true Z, Y, A phien ma tao ra cac phan tu mARN tuang ung.
Cau 6: Mot gen c6 tong s6 2128 lien kk hidro. Tren mach 1 cua gen c6 so nucleotit
loai A bang so nucleotit loai T; so nucleotit loai G gap 2 Ian so nucleotit loai A; so nucleotit
loai X gap 3 Ian so nucleotit loai T. So nucleotit loai A ciia gen la
A. 112.
B.448.
€.224.
D. 336.
Cau 7: Muc do c6 Igi hay c6 hai ciia gen dot bien phu thugc vao

A. tan so phat sinh dot bien.
B. so lugng ca the trong qu4n the.
C. ti le due, cai trong quan the.
D. moi truang song va to hgp gen.
Cau 8: Alen D c6 3600 lien ket hidro va so nucleotit loai A chiem 30% tong so nucleotit
ciia gen. Alen D bi dot bien mk mot cap A - T thanh alen d. Mot te bao c6 cap gen Dd
nguyen phan mot Ian, so nucleotit moi loai ma moi truang ngi bao cung cap cho cap gen
nay nhan doi la:
A . A = T = 1799;G = X = 1200.
B . A = T = 1800; G = X = 1200.
^
C. A = T = 1199; G = X = 1800.
D. A = T = 899; G = X = 600.
Cau 9: Moi gen ma hoa protein dien hinh c6 3 vung trinh tu nucleotit. Viing trinh tu
nucleotit nam a dau 5' tren mach ma goc ciia gen c6 chuc nang mang tin hieu
A. ma dau qua trinh phien ma.
B. ket thiic qua trinh dich ma.
C. ma dau qua trinh dich ma.
i"l>; k6tthttetjua:tftnh phi4ftBilL
^


Sir dung thong tin diroi day cho cac cau hoi 10 - 16:
Dieu hoa hoat dong cua gen
Khi nghien curu E. coli, mot loai vi khuan rat pho bien trong rupt ket ciia nguoi va
cac dong vat c6 vu khac, cac nha khoa hoc da thay mot hien tuong rat thii vi nhu sau:
Khi moi tnrong thieu (hoac khong c6) axit amin triptophan, mot loai axit amin r§t
can thiet cho sy ton tai ciia vi khuan, te bao vi khuan se dap ling lai bang viec boat boa
mot con duong cbuyen boa de tu tong bop triptophan tir mot loai chat kbac trong moi
truong. Nhung sau do, khi ca the sinb vat chu tieu boa mot loai thuc an giau triptophan

tbi te bao vi khuan se dung ngay viec san xuat triptophan; nbo vay no tranh dugc viec
lang phi nguon dinh duong.
Co che cho phep td bao tong hop hoac dung san xuat triptophan dugc goi la ca cb^
dieu boa operon Trp va dugc mo ta nhu trong hinb ve dual day:
Gen dieu hoa
AON;

SI

trpB

mARN

Vung van hanh

ARN
pollmeraza

operon Trp
Cac gen ciia operon

B6 ba mcr u B6 ba ket
mARN 5' ^ M S H M ^ B B H

Protein i ^ ^ ^ ^ P r o t e i n irc che Strang thai
u'c che
Vhbnz hoat dong

Cac tieu phan polipeptit cau tao nen
cac enzim sinh tong hgrp triptophan

(a) Khi thieu triptophan, protein irc che bj bat hoat, operon Trp b| "tat"
ARN khong
du'QTc t^o ra

nnARN
Protein U'C che
or d^ng hoat dong . ; " J i ' . i

Protein
irc che
^Triptophan

(b) Khi CO triptophan, protein u'c che hoat dong, operon Trp bj "tat"

Cau 10: Trong ca che dieu boa operon Trp a vi khuan E. coli, gen dieu boa c6 vai tr6
A. mang thong tin cho viec tong bgp mot loai protein uc cbg tac dong len vung van
hanh cua operon Trp.
B. mang thong tin cho viec tong bgp cac chu6i polipeptit cau tao nen cac enzim sinb
tong bgp triptophan.
C. la noi ma ARN polimeraza bam vao va khai dau phien ma.
D. la noi ma protein uc che bam vao de uc che qua trtnh phien ma.


Cau 11: Trong ca che dieu hoa operon Trp, khi trong moi tnrong c6 triptophan thi c6 the
dien ra cac sir kien sau:
1. Gen dieu hoa chi huy tong hap mot loai protein uc che.
2. Protein urc che a trang thai bat hoat, khong gan vao vimg van hanh ciia operon Trp. ^
3. Triptophan gan vai protein uc che, lam protein urc che a dang hoat dpng.
4. ARN polimeraza gan vao operon Trp tai viing van hanh va phien ma cac gen cua

operon.
5. Protein urc che d dang hoat dgng lien ket vdi viing van hanh va ngan can sir phien ma
cac gen ciia operon Trp.
Co bao nhieu sir kien diing?
*
'
A. 2
B.3
C.4
D.5
Cau 12: Dieu gi se xay ra doi vai operon Trp khi te bao su dung can kiet nguon dir trii
triptophan cua no?
Cau 13: Cung d vi khuan E. coli, cac nha khoa hoc con phat hien them mot co che dieu
hoa operon Lac. Hay dir doan khi trong moi tnrong khong c6 lactozo thi co che di8u hoa
operon Lac se nhu the nao?
Cau 14: Neu mot dot bien lam thay doi trinh tir viing van hanh cua operon Lac dan den
viec protein lie che khong co kha nang lien ket vao do thi sir tong hop P-galactozidaza
cua te bao bi anh huang nhu the nao?
Cau 15: Neu mot operon nhat dinh ma hoa cho cac enzim tong hop mot loai axit amin
thiet yeu va dugc dieu hoa giong vdi operon Trp thi
A. axit amin do se gay bat hoat chat uc che.
B. axit amin do gan voi vung van hanh ciia operon va ngan can qua trinh phien ma. >
C. axit amin do gan voi protein lic che, chuyen protein lic che sang dang hoat dpng.
D. protein lic che se hoat dong khi trong moi tnrong khong co axit amin do.
Cau 16: Trong co the nguoi, cac te bao than kinh va cac tS bao co khac nhau chii yeu vi chUng
A. chiia cac gen khac nhau.
B. sii dung cac ma di truyen khac nhau.
C. CO sir bieu hien ciia cac gen khac nhau. D. co cac nhiem sac the khac nhau.
Cau 17: Cho cac phat bieu sau day noi \h qua trinh nhan doi ADN:
(1) Qua trinh nhan doi ADN dien ra theo nguyen tac bo sung va ban bao loan.

(2) Qua trinh nhan doi ADN bao gia ciing diln ra d6ng thai vdi qua tnnh phien ma.
(3) Tren ca hai mach khuon, ADN pohmeraza deu di chuyen theo chieu 5' 3' de
tong hop mach moi theo chieu 3' ^ 5 ' .
(4) Trong moi phan tii ADN duoc tao thanh thi mot mach la mai dugc tong hop, con
mach kia la ciia ADN ban dau.
* iv^m
(5) Cac mach moi deu dugc tong hgp lien tuc.
Trong cac phat biSu tren, c6 bao nhieu phat bilu khong dung?
'
A.l

B.3

C.2

D.4

.^^^J^-,

m


Cau 18: Biet cac bp ba tren mARN ma hoa cac axit amin tuong ung nhu sau: 5'XGA3'
ma hoa axit amin acginin; 5'UXG3' va 5'AGX3' cung ma hoa axit amin xerin; 5'GXU3'
ma hoa axit amin alanin. Biet tiinh tir cac nucleotit a mot doan tren mach goc cua vung
ma hoa a mot gen cku true cua sinh vat nhan so la 5'GXTTXGXGATXG3'. Doan gen
nay ma hoa cho 4 axit amin, theo li thuyet, trinh tir cac axit amin tucmg ung vai qua trinh
dich ma la
A. acginin - xerin - alanin - xerin.
B. xerin - acginin - alanin - acginin.

C. xerin - alanin - xerin - acginin.
D, acginin - xerin - acginm - xerin.
Cau 19: Phan tur tARN mang axit amin foocmin metionin 6 sinh vat nhan so c6 bp ba doi ma
(anticodon) la
A.5'AUG3'.
B.5'UAX3'.
C.3'AUG5'. D.3'UAX5'.
Cau 20: Mot gen c6 900 cap nucleotit va c6 ti le cac loai nucleotit bang nhau. So lien ket
hidro cua gen la
A. 1798.
B.1125.
C. 2250.
D.3060.
HUdNG DAN GIAI
Cau 1: 1. Tile % nucleotit moi loai tren moi mach dom cua gen:
A, = T 2 = 10%; T i = A 2 = 30%; G i - X 2 = 40%; X, = G 2 = 20%.
2. Ti le % nucleotit moi loai cua gen: A = T = 20%; G = X = 30%.
Cau 2: 1. Neu so lugng lien ket hidro ciia gen sau dot bien khong doi thi dang dot bien
xay ra la thay the mot cap nucleotit cung loai (vi du thay the cap A - T bang cap T - A
hoac thay the cap G - X bang cap X - G).
2. Neu so lugng lien ket hidro ciia gen sau dot bien thay doi thi c6 hai truong hop:
- Truong hpp 1; Thay thg cap A - T hkng cap G - X thi s6 lugng nucleotit m6i loai
ciia gen la A = T = 719; G = X = 481.
- Truong hgp 2: Thay thS cap G - X bSng cap A - T thi so lugng nucleotit moi loai
ciia gen la A = T = 721; G = X = 479.
Cau 3: Dang dot bien xay ra vai alen A la dot bien thay the mot cap nucleotit nay bSng
cap nucleotit khac nhung ca hai bp ba truac va sau dot bien ddu cung ma hoa cho mot axit
amin (tinh thoai hoa ciia ma di truyen) nen chuoi polipeptit do cac alen A va a tong hgp
deu hoan toan giong nhau ve so lugng, thanh phan va trinh tu sap xep cac axit amin.
Cau 4: 15 572 lien ket hidro dugc hinh thanh.

Cau5:C Cau6:C Cau7:D Cau 8: A Cau9:D Cau 10: A Cau 11: B
Cau 12: Khi khong con triptophan, protein uc che se tra ve trang thai ban dau khong hoat
dpng, khong gan dugc vao viing van hanh ciia operon Trp nua va su phien ma cac gen
thupc operon Trp lai dugc phuc hoi.
Cau 13: Khi moi truong khong c6 lactoza, chit uc chi a trang thai hoat dpng gin vai
vung van hanh, ngan can qua trinh phien ma ciia cac gen a operon Lac, do do enzim
P-galactozidaza khong dugc tong hgp.
Cau 14: Te bao se tong hgp lien tuc (3-galact6zidaza du trong moi truong c6 hay khong
CO lactoza, do vay se lam lang phi tai nguyen ciia te bao.
Cau 15: C Cau 16: C. Cau 17: B. Cau 18: D Cau 19: D Cau 20: C


CHU DE 2. CO S6 TE BAO CUA HIEN TaONG DI TRUYEN VA BIEN D!
I.

KIEN THUfC CO BAN

1. Vat chat di truyen 6 cap dp te bao la nhiim sac the
- d sinh vat nhan so, moi te bao chi chua mot phan tu A D N tran, khong lien k i t voi
protein, xoan kep va c6 dang vong (chua c6 cau true NST). 6 sinh vat nhan thuc, vat chat
di truyen a cap do te bao la nhiem sic the (NST). NST dugc ciu tao bai A D N lien kk voi
cac loai protein khac nhau (chii yeu la protein histon).
- Moi NST do mot phan tu A D N lien ket vai rat nhieu phan tu protein va co xoan lai
a cac muc khac nhau: A D N (2nm) —> Chuoi nucleoxom
Sod co ban (1 Inm) —>• Sgi chat
nhiem sic (30nm) — Sieu xoAn (300nm)
Cromatit (700nm). Do vay, hinh thai NST
bien doi trong chu ki te bao.
- Co hai loai NST: NST thuong va NST giai tinh.
- Moi loai co bo NST dac trung ve so lugng, hinh thai

cau true. So luong NST
nhieu hay it khong phan anh muc do tien hoa ciia loai. Tap hop cac NST co trong nhan
ciia te bao dugc goi la bo NST.
+ Bo NST luong boi (2n) co trong te bao xoma, hop tu, te bao sinh due so khai,
te bao sinh tinh va te bao sinh tning. Trong cac te bao nay, NST thuong ton tai thanh tung
cap tuong dong giong nhau ve hinh thai, kich thuac va trinh tu phan bo gen.
+ Bo NST don boi (n) co trong giao tu. Trong giao tu, NST ton tai thanh tung chiec.
- NST la cau triic mang gen. Moi gen co vi tri (locut) xac dinh tren NST.
- Chuc nang cua NST: luu tru, bao quan, truyen thong tin di truyen; giiip te bao phan
chia deu vat chat di truyen cho te bao con va dieu hoa boat dong cac gen thong qua mire
do dong hay thao xoSn cua NST.

2. Cd che cua hien ti/dng di truyen va bien dj 6 cap dp te bao
- Sir nhan doi, phan l i va to hop binh thuong ciia cac NST trong cac qua trinh
nguyen phan, giam phan va thu tinh la ca che duy tri su on dinh bo NST dac trung ciia
moi loai qua cac the he.
- Su trao doi cheo giira cac cromatit khac ngu6n ciia cap NST tuong dong a ki dau
giam phan I , su phan l i doc lap ciia cac NST kep ki sau I , su to hop tu do ciia cac loai
giao tu due va cai trong qua trinh thu tinh la co che tao nen cac bien di to hgrp.
- Qua trinh nhan doi va phan l i khong binh thuong ciia nhilm sac the lam phat sinh
cac dang dot bien cau true va dot bien so lugng NST cung la mot co che quan trong ciia
hien tugng bien di a cap do te bao.

3. Dot bien cau true nhiem sac the
- La su bien doi xay ra trong c§u true ciia NST (them, bat hoac sap x i p lai nhirng
khoi gen tren hoac giua cac NST), co the lam thay doi hinh dang va cau true NST.
- Ca che phat sinh:
+ Do tac nhan dot bien lam dut gay NST sau do noi lai mot each khong binh thuong.
+ Do roi loan qua trinh trao doi cheo (trao doi khong can giCra cac cromatit cua cap
NST tuong dong hoac trao d6i giira cac NST khong tuong d6ng).

21


,3

Quayl80g$.dlrtf>tf^l^vjtric0

0^
( j a c nhan gay dot bien )
Dlnhv>ovitrim»ltrtnK8Ta6
Pha vo" c l u true, mot
dean NST bj dirt ra

NST khi dang nhan doi hoac
tiep hap, trao doi cheo

Cftijy^n do^n Irong cung NST

Dinh vAo NST hwmg d i n g

Mil aim
iDlnhvtoWSTkhdngUfcmflg&ng /
^ C h u y i n do^n khflng tirong h i

Trao d i l Ohio khftng c t n
Mk do^n
gMfacie NST tuong d i n g /

\iip

R6i loan trao dSl cheo

4.

Trao d i l dofn giOa c&c
iNSTkhangtwmgding

,
ChuySn (foqn Itrong M

D o t b i e n s o li/dng n h i e m sac t h e

- La sir thay doi ve so lugng NST trong te bao. Sir thay doi nay c6 the xay ra a mot
hay mot vai cap NST (dot bien lech boi) hoac 6 tat ca cac cap NST (dot bien da boi).
- Dot bien lech boi: la sir thay doi a mot hoac mot vai cap NST tuong dong. 0 bac
trung hoc pho thong chi xet truong hop thay doi a mot cap NST.
- Dot bien da boi: la sir thay doi ve so lugng NST a tat ca cac cap trong te bao.
Co hai dang dot bi^n da boi la tir da boi va di da boi.
+ Tir da boi la sir tang len mot so nguyen Ian bo NST don boi ciia loai va Ion han 2n.
+ Dj da boi la sir tang mot s6 nguyen Van bo NST don boi cua 2 loai khac nhau
(ca hai bo NST cua 2 loai khac nhau cung ton tai trong mot te bao).
Themot(2n-l)

The ba (2n+l)

TTie bon (2n+2)

The khong {2n-2)

tPotbien lech bolt

Te bao binh thircmg
(2n)

Dot bien da boi

The tiy boi (4n)

The tarn boi (3n)

Mot SO dang dot bien so lugng NST


- Ca chS phat sinh dot biln lech boi tir te bao binh thuong (2n):
Qua trinh nguyen phan

Qua trinh

binhthw&ng

le bao binh th(rtmg(2n)

nguyenphon

khong binh thw&ng

'nteba(2n4l) The mpt (2n-l) The bon |2IH^2] The khong |2n-2)

Ca che phdt sinh dot bien lech boi trong qua trinh nguyen phan

+ Trong qua trinh nguyen phan, mot NST kep cua cap NST tuong dong khong phan
H CO the tao ra cac t^ bao dot bien (2n + 1) va (2n - 1). Neu ca hai NST kep ciia cap NST
tuong dong deu khong phan li, cung di ve mot cue cua te bao thi c6 the tao ra cac te bao dot
bi^n (2n + 2) va (2n - 2). NIU qua trinh nay xay ra a te bao sinh duong thi se xuat hien the
kham (ca the c6 cac mo chua te bao lech boi va cac mo binh thuong).
Qua trinh gidm phan

Qua trinh giam phan

binhthwomg

khong binh thw&ng

Theba(2n+1)

The mpt(2n-l)

Ca che phdt sinh dot bien lech boi trong qud trinh gidm phan vd thu tinh

23


+ Trong qua trinh giam phan, mot cap NST khong phan U 6 ki sau I tao ra giao tu
thua NST (n + 1) va thi^u NST (n - 1). Khi thu tinh, giao tu dot bikn (n ± 1) kk hop voi
giao tu binh thucmg (n) tao ra the ba (2n + 1) hoac the mot (2n - 1). NIU cac giao tii dot biln
(n + 1) ket hop voi cac giao tu dot bien (n + 1) thi c6 th^ tao ra cac thk dot hikn thi b6n
(2n + 2). Neu cac giao tu dot bien (n - 1) kk hop voi cac giao tu dot bien (n - 1) thi c6
the tao ra cac the dot bien the khong (2n - 2).
- Co che phat sinh dot bien tu da boi tu te bao binh thudng (2n):
+ Trong qua trinh nguyen phan: Neu tat ca cac cap NST d§u khong phan li c6 thS tao

thanh te bao 4n. Neu dot bien xay ra trong ikn nguyen phan dSu tien cua hop tu c6 ihk tao
thanh ca the tu boi (4n). Neu dot bidn xay ra d tS bao xoma thi tao thanh thk kham (vi du
canh 4n tren cay luong boi).
+ Trong qua tiinh giam phan: NSu t^t ca cac cap NST dku khong phan li (trong giam
phan I) se tao thanh giao tu dot biSn (2n). Giao tii dot hi&n (2n) c6 thk kk hop voi giao tu
binh thuong (n) tao thanh thS tam boi (3n) hoac c6 the kk hop voi giao tii (2n) tao thanh
the tii boi (4n).
- So do tong quat ca che phat sinh dot bien s6 lugng NST:
/2n + 1 (The ba)
1 N S T k e p k h o n g p h a n li
2n - 1 (The m g t )
Ca 2 NST kep cua cap NST

Nguyen

phan

t i / c n g d b n g k h o n g p h a n li

2n + 2 (The bon)
\ 2 n - 2 (The khong)

^ Tat ca cac NST khong phan

4 n (The ti> bgi)
f

Te bao 2n
irjn
Giao tLf

1 c a p N S T k h o n g p h a n li

+l)/

+ n - . 2n + 1 (The ba)

\ (n +

( t r o n g g i a m p h a n I)

1)

2n + 2 (The bon)

+ ( n - l ) - . 2 n - 2 ( T h e mpt)
\ G i a o t i^>(( n -- l ) / " ' " - ^ ' ^ ^ " \ + ( n - ll ) - .. 22 nn--2 ( T h e khong)

Giam phan
T a t c a c a c N S T k h o n g p h a n li

Giaotif2n

( t r o n g g i a m p h a n I)

/ + " ^ 3 " (The tarn boi)

<:

y

2n — 4 n (The tur bgi)

- Ca chk phat sinh dot bi^n di da boi: 2nAA x 2nBB
(nA + nB) (b§t thu)
Da boi hoa —• (2nAA + 2nBB) (the song nhi boi, c6 kha nang sinh san binh thucmg).
5.

Hau q u a c u a dot bien n h i e m s a c the

5.1. Hau qu^ cua dot bien cau true nhiem sac the

Dot bien
Mat doan

Hau qua

Vidu

Giam so luong gen tren NST, lam Mat mot phan vai ngSn NST s6 5
mat can bang he gen nen thuong gay gay hoi chiing meo keu, mat mot
chet d6i voi thg dot biSn
doan NST so 21 gay ung thu mau,...

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