Transcript Essential Cell Biology

Alberts • Bray • Hopkin • Johnson • Lewis • Raff • Roberts • Walter
Essential
Cell Biology
FOURTH EDITION
Chapter 5
DNA and Chromosomes
Copyright © Garland Science 2014
Microscopy revealed chromosome bodies that
are segregated to daughter cells during cell division.
Fig. 5-1
T. H. Morgan used Drosophila genetics and the giant
chromosomes from their salivary glands to show
that chromosomes contain the genetic information.
-1920s
Drosophila genetics
Giant polytene chromosomes
In larval salivary glands
DNA Component of Chromosomes Contains
Genetic Information for Virulence
virulent
nonvirulent
Purified DNA (not
protein) from
heat-killed S strain
also transformed.
Fig. 5-3
DNA Component of Bacterial Virus
Also Contains Its Genetic Information
Fig. 5-5
Watson and Crick Determined Structure of DNA in 1950s
four different
deoxyribonucleotide
building blocks
complementary
base pairing
Fig. 5-2
right-handed
double helix
The data came from Rosalind Franklin, who
was not awarded Nobel Prize posthumously.
Complementary Base Pairing
Fig. 5-6
data from Chargaff suggested base pairing
Like many others, DNA is a linear code:
English
musical scale
Morse code
Chinese
DNA
Fig. 5-8
Linear Code of DNA decoded into linear array
of amino acids in protein (w/ RNA as intermediate).
Fig. 5-9
Double-stranded character of DNA immediately
suggested a mechanism for heredity.
Each strand provides a template for
duplicating the DNA before cell division.
Fig. 5-14
Complementary base pairing also provides the basis
for many molecular biology techniques:
Southern blotting allows labeling of a specific gene
on nitrocellulose paper.
Fig. 10-5
Every gene in genome can be
probed on a microarray.
Fragment of
every gene
in genome on slide
Fig. 10-5,-29,-30
Labeled DNA can also be hybridized
to DNA on chromosomes
or RNA in
tissues
mouse brain
Specialized Chromosome Regions Are Needed
for Replication and Segregation During Mitosis
Fig. 5-15
Most of the DNA Decondenses During Interphase
stays condensed
The decondensed
DNA is called
euchromatin.
Fig. 5-18
Heterochromatin Flanks Two Specialized Regions
Needed for Chromosome Segregation
also regulates
expression of
some genes
Fig. 5-28
DNA is Packaged with Proteins in Chromosomes
Electron Microscopy
Fig. 5-24
X-Ray Crystal Structure
of Nucleosome
Fig. 5-22
Histone H1 Alters Path of Linker DNA,
Allowing Further Compaction to 30 nm Fiber
Fig. 5-23
ATP-Dependent Nucleosome Plows Loosen
Chromatin for Gene Expression
Fig. 5-26
Covalent Modifications on Histone N-Terminal Tails
Also Affect Chromatin Structure
Fig. 5-27
N-Terminal Modifications Provide a Histone Code
Heterochromatin Protein 1
TATA-Binding Protein
mitosis
Fig. 5-27
modifications allow binding
of non-histone chromatin proteins
Heterochromatin Assembly Involves
Binding of HP1 to H3-MeK9
H3-MeK9
& HP1
HP1
Fig. 5-26
Heterochromatin is a Heritable
Inactive Chromatin State
Epigenetic:
heritable state
that acts above
the level of
gene sequence
Fig. 5-30