bacterial cell phage head tail sheath tail fiber dna 100 nm 1

12
Bacterial cell Phage head Tail sheat h Tail fiber DNA 100 nm 1

Upload: quentin-moore

Post on 02-Jan-2016

233 views

Category:

Documents


0 download

TRANSCRIPT

Page 1: Bacterial cell Phage head Tail sheath Tail fiber DNA 100 nm 1

Bacterial cell

Phage head

Tail sheath

Tail fiber

DNA

100

nm

1

Page 2: Bacterial cell Phage head Tail sheath Tail fiber DNA 100 nm 1

EXPERIMENT

Phage

DNA

Bacterial cell

Radioactive protein

Radioactive DNA

Batch 1: radioactive sulfur (35S)

Batch 2: radioactive phosphorus (32P)

Empty protein shell

Phage DNA

Centrifuge

Centrifuge

Pellet

Pellet (bacterial cells and contents)

Radioactivity (phage protein) in liquid

Radioactivity (phage DNA) in pellet

2

Page 3: Bacterial cell Phage head Tail sheath Tail fiber DNA 100 nm 1

Sugar–phosphate backbone

5 end

Nitrogenous

bases

Thymine (T)

Adenine (A)

Cytosine (C)

Guanine (G)

DNA nucleotide

Sugar (deoxyribose)

3 end

Phosphate

3

Page 4: Bacterial cell Phage head Tail sheath Tail fiber DNA 100 nm 1

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

4

Page 5: Bacterial cell Phage head Tail sheath Tail fiber DNA 100 nm 1

(c) Space-filling model

Hydrogen bond 3 end

5 end

3.4 nm

0.34 nm

3 end

5 end

(b) Partial chemical structure(a) Key features of DNA structure

1 nm

5

Page 6: Bacterial cell Phage head Tail sheath Tail fiber DNA 100 nm 1

Purine + purine: too wide

Pyrimidine + pyrimidine: too narrow

Purine + pyrimidine: width consistent with X-ray data

6

Page 7: Bacterial cell Phage head Tail sheath Tail fiber DNA 100 nm 1

Cytosine (C)

Adenine (A) Thymine (T)

Guanine (G)

7

Page 8: Bacterial cell Phage head Tail sheath Tail fiber DNA 100 nm 1

A T

GC

T A

TA

G C

(a) Parent molecule

A T

GC

T A

TA

G C

(c) “Daughter” DNA molecules, each consisting of one parental strand and one new strand

(b) Separation of strands

A T

GC

T A

TA

G C

A T

GC

T A

TA

G C

8

Page 9: Bacterial cell Phage head Tail sheath Tail fiber DNA 100 nm 1

Origin of replication Parental (template) strand

Daughter (new) strand

Replication fork

Replication bubble

Two daughter DNA molecules

(a) Origins of replication in E. coli

Origin of replication Double-stranded DNA molecule

Parental (template) strandDaughter (new) strand

Bubble Replication fork

Two daughter DNA molecules

(b) Origins of replication in eukaryotes

0.5 µm

0.25 µm

Double-strandedDNA molecule

9

Page 10: Bacterial cell Phage head Tail sheath Tail fiber DNA 100 nm 1

A

C

T

G

G

G

GC

C C

C

C

A

A

AT

T

T

New strand 5 end

Template strand 3 end 5 end 3 end

3 end

5 end5 end

3 end

Base

Sugar

Phosphate

Nucleoside triphosphate

Pyrophosphate

DNA polymerase

10

Page 11: Bacterial cell Phage head Tail sheath Tail fiber DNA 100 nm 1

DNA double helix (2 nm in diameter)

Nucleosome(10 nm in diameter)

Histones Histone tailH1

DNA, the double helix Histones Nucleosomes, or “beads on a string” (10-nm fiber)

11

Page 12: Bacterial cell Phage head Tail sheath Tail fiber DNA 100 nm 1

30-nm fiber

Chromatid (700 nm)

Loops Scaffold

300-nm fiber

Replicated chromosome (1,400 nm)

30-nm fiber Looped domains (300-nm fiber)

Metaphase chromosome

12