CH. 17: Control of Gene Expression in Eukaryotes Notes

Chapter 17: Control of Gene
Expression in Eukaryotes
17.1 Eukaryotic Cells and Bacteria Have Many Features of
Gene Regulation in Common, but They Diff er in Several
Important Ways
 Each structural gene has its own promoter and is transcribed
separately.
 DNA must unwind from the histone proteins before transcription.
 Transcription and translation are separated in time and space.




Figure 1 Chromatin has a highly complex structure with
several levels of organization.

 Chromosome puffs are regions of
relaxed chromatin where active
transcription is taking place
 DNAse I digests DNA that are NOT
tightly bound to histones
 What is the nature of the change in
chromosome puffs and DNA
sensitivity?

, 17.2 Changes in Chromatin Structure Aff ect the Expression
of Genes
- DNase I
hypersensitivity
o DNase I
hypersensitive
sites: more
open chromatin
configuration
site, upstream
of the
transcription
start site
- Histone
modification
o Addition of
methyl groups
(CH3) to the
histone protein
tails (lysine or
arginine)
o Addition of Figure 2 The acetylation of histone proteins alters chromatin structure and permits some
acetyl groups transcription factors to bind to DNA.

(CH3CO) to histone proteins (Lysine)


- Acetylation of histones controls flowering in Arabidopsis
o Flowering locus C (FLC) gene
o Flowering locus
D (FLD) gene
- Chromatin
remodeling
o Chromatin-
remodeling
complexes: bind
directly to DNA
sites and
reposition
nucleosomes
- DNA methylation