Ôn tập sinh học tdl121 gen 05 dna

21/04/01

DNA

Materials were extracted from
Hartwell et al., 2018. Genetics: from genes to genomes 6th edition,
Brooker, 2017. Genetics Analysis and Principles 6th edition và

Pierce, 2016. Genetics: a conceptual approach 6th edition
except cited otherwise

1

Content
• Function
• Structure
• Replication
• Recombination
• Repair

2

1


21/04/01

DNA function

3

Smooth and rough colonies of Streptococcus pneumoniae

Hartwell et al.., 2017

4

2


21/04/01

Griffith’s experiments on genetic transformation

Brooker, 2017

5

Avery’s experiments on genetic transformation

Hartwell et al., 2017

6

3


21/04/01

Bacteriophage T2 structure and life cycle

Hartwell et al., 2017

7

Hershey-Chase waring blender experiment

DNA is the genetic material
Hartwell et al., 2017

8

4


21/04/01

DNA structure

9

DNA
• DNA is a polymer
• monomer is nucleotides
• phosphodiester bonds
• nucleotide: phosphate, deoxyribose,
nitrogenous base

Brooker, 2017

10

5


21/04/01

The components of nucleotides

5-methylcytosine

Brooker, 2017

11

The structure of nucleotides

Brooker, 2017

12

6


21/04/01

Nucleotide and nucleic acid nomenclature

13

DNA

• DNA is a polymer
• monomer is nucleotides
• phosphodiester bonds
• nucleotide: phosphate, deoxyribose,
nitrogenous base

• Usually double stranded
• antiparallel
• hydrogen bond

Alberts et al., 2015

14

7


21/04/01

DNA
• DNA is a polymer
• monomer is nucleotides
• phosphodiester bonds
• nucleotide: phosphate, deoxyribose,
nitrogenous base

• Usually double stranded
• antiparallel
• hydrogen bond
• popular B form: right-handed, 2 nm in

diameter, 10 bp/turn, 3.4 nm/turn
Alberts et al., 2015

15

B-form double helix

Urry et al., 2021

16

8


21/04/01

Comparison of the structures of B DNA and Z DNA

right-handed
10 bp/turn
low ionic strength

left-handed
12 bp/turn
high ionic strength
methylated

Brooker, 2017

17

DNA replication

18

9


21/04/01

Three possible models for DNA replication

Brooker, 2017

19

The Meselson–Stahl DNA replication experiment
Lyse the cells

Centrifuge
CsCl gradient

N14

N15

Generations
Meselson and Stahl, 1958

0

0.3

0.7

1.0

1.1

1.5

1.9

2.5

3.0

DNA replication is semiconservative

4.1

20

10


21/04/01

Bacterial DNA replication
• Started at origin of replication

Brooker, 2017

21

Bacterial DNA replication
• Started at origin of replication
• Required many proteins

Brooker, 2017

22

11


21/04/01

Bacterial DNA polymerases

Subunits of the DNA polymerase III holoenzyme

Klug et al., 2019

Brooker, 2017

23

Bacterial DNA replication
• Started at origin of replication

• Required many proteins
• Required RNA primers

Brooker, 2017

24

12


21/04/01

Bacterial DNA replication
• Started at origin of replication
• Required many proteins
• Required RNA primers
• Synthesized in 5’→3’ direction

Brooker, 2017

25

The proofreading function of DNA polymerase

The 3′ end enters
the exonuclease site

At the 3′ exonuclease site, the strand
is digested in the 3′ to 5′ direction until
the incorrect nucleotide is removed

Brooker, 2017

26

13


21/04/01

Bacterial DNA replication
• Started at origin of replication
• Required many proteins
• Required RNA primers
• Synthesized in 5’→3’ direction
• Bidirectional

Brooker, 2017

27

A being replicated E. coli chromosome

Brooker, 2017

28

14

21/04/01

A three-dimensional view of DNA replication

Brooker, 2017

29

The synthesis of DNA fragments on the lagging strand

Alberts et al., 2016

30

15


21/04/01

Bacterial DNA replication
• Started at origin of replication
• Required many proteins
• Required RNA primers
• Synthesized in 5’→3’ direction
• Bidirectional
• Terminated at termination sequence

Brooker, 2017

31

Eukaryotic DNA replication

32

16


21/04/01

Eukaryotic chromosomes have multiple origins of replication

Alberts et al., 2018

Booker, 2017

33

Replication of eukaryotic chromosomes

Booker, 2017

34

17


21/04/01

Not all origins of replication are used

10%

90%

Alberts et al., 2016

35

Formation of a prereplication complex in eukaryotes

ORC: origin recognition complex

Booker, 2017

36

18


21/04/01

Eukaryotic DNA Polymerases

37

Removal of an RNA primer by flap endonuclease

Booker, 2017

38

19


21/04/01

Formation of nucleosomes behind a replication fork

Alberts et al., 2016

39

Chromosome telomeres

Booker, 2017

40

20


21/04/01

The enzymatic action of telomerase

Booker, 2017

41

DNA recombination

42

21


21/04/01

Double-strand break formation

Hartwell et al., 2018

43

Resection

Hartwell et al., 2018

44

22


21/04/01

First strand invasion

Hartwell et al., 2018

45

Crossover pathway: formation of a double Holliday junction

Hartwell et al., 2018

46

23


21/04/01

Crossover pathway: branch migration

Hartwell et al., 2018

47

Crossover pathway: resolution of the double Holliday junction

Hartwell et al., 2018

48

24


21/04/01

First strand invasion

Hartwell et al., 2018

49

Noncrossover pathway

Hartwell et al., 2018

50

25