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DNA. 1/22/09. The homonculus. The Different Parts of a Nucleotide. Nitrogenous Base. Phosphate. Sugar. Fig. 16-5. Nitrogenous bases. Sugar–phosphate backbone 5  end. Thymine (T). Adenine (A). Cytosine (C). DNA nucleotide. Phosphate.

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DNA

1/22/09

The homonculus


The different parts of a nucleotide
The Different Parts of a Nucleotide

Nitrogenous Base

Phosphate

Sugar


Fig. 16-5

Nitrogenous bases

Sugar–phosphate backbone 5 end

Thymine (T)

Adenine (A)

Cytosine (C)

DNA nucleotide

Phosphate

Sugar (deoxyribose) 3 end

Guanine (G)


Percentage of nitrogenous bases in four organisms
Percentage of Nitrogenous Bases in Four Organisms

Source of DNA A T G C

Streptococcus 29.8 31.6 20.5 18.0

Yeast 31.3 32.9 18.7 17.1

Herring 27.8 27.5 22.2 22.6

Human 30.9 29.4 19.9 19.8


Fig. 16-6

(b) Franklin’s X-ray diffraction photograph of DNA

(a) Rosalind Franklin


Fig. 16-7a

5 end

Hydrogen bond

3 end

1 nm

3.4 nm

3 end

0.34 nm

5 end

(a) Key features of DNA structure

(b) Partial chemical structure


Fig. 16-8

Adenine (A)

Thymine (T)

Cytosine (C)

Guanine (G)


Fig. 16-12

Origin of replication

Parental (template) strand

Daughter (new) strand

Replication fork

Double-

stranded

DNA molecule

Replication bubble

0.5 µm

Two daughter DNA molecules

(a) Origins of replication in E. coli

Origin of replication

Double-stranded DNA molecule

Parental (template) strand

Daughter (new) strand

0.25 µm

Replication fork

Bubble

Two daughter DNA molecules

(b) Origins of replication in eukaryotes


Fig. 16-14

New strand 5 end

Template strand 3 end

5 end

3 end

Sugar

T

A

A

T

Base

Phosphate

C

G

C

G

G

C

G

C

DNA polymerase

3 end

A

A

T

T

3 end

Pyrophosphate

C

C

Nucleoside triphosphate

5 end

5 end


Fig. 16-15

Overview

Origin of replication

Leading strand

Lagging strand

Primer

Lagging strand

Leading strand

Overall directions of replication

Origin of replication

3

5

RNA primer

5

“Sliding clamp”

3

5

DNA poll III

Parental DNA

3

5

5

3

5


Fig. 16-16a

Overview

Origin of replication

Leading strand

Lagging strand

Lagging strand

2

1

Leading strand

Overall directions of replication


Fig. 16-16b1

3

5

3

5

Template strand


Fig. 16-16b2

3

5

3

5

Template strand

3

5

3

RNA primer

1

5


Fig. 16-16b3

3

5

3

5

Template strand

3

5

3

RNA primer

1

5

3

Okazaki fragment

5

3

1

5


Fig. 16-16b4

3

5

3

5

Template strand

3

5

3

RNA primer

1

5

3

Okazaki fragment

5

3

1

5

3

5

3

2

5

1


Fig. 16-16b5

3

5

3

5

Template strand

3

5

3

RNA primer

1

5

3

Okazaki fragment

5

3

1

5

3

5

3

2

5

1

5

3

3

5

1

2


Fig. 16-16b6

3

5

3

5

Template strand

3

5

3

RNA primer

1

5

3

Okazaki fragment

5

3

1

5

3

5

3

2

5

1

5

3

3

5

1

2

5

3

3

5

1

2

Overall direction of replication


Fig. 16-18

Nucleotide Excision Repair

Nuclease

DNA polymerase

DNA ligase


Fig. 16-19

5

Ends of parental DNA strands

Leading strand

Lagging strand

3

The chromosome end replication problem

Last fragment

Previous fragment

RNA primer

Lagging strand

5

3

Parental strand

Removal of primers and replacement with DNA where a 3 end is available

5

3

Second round of replication

5

New leading strand

3

5

New lagging strand

3

Further rounds of replication

Shorter and shorter daughter molecules



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