http://cellbio.utmb.edu/cellbio/nucleus2.htm
 

What we discussed in lecture........
 

Chromatin configuration and changes as a means of "globally " regulating transcription in development
 

A. Hypersensitive sites can predict future transcriptional activity
 

[Remember that we have roughly defined determination as the capacity for expression of gene subsets; differentiation as over expression]
 

What changes occur at hypersensitive sites?
 

1. DNase sensitivity (by definition). This is correlated with induced transcription, e.g. hor,onal induction
 

2. histone modifications such as an altered H1 interaction and acetylation of the core histone amino acids (terminal tails)
 

3. degree of methylation
 

4. relationship to presence of HMG 14/17
 

B. Locus control regions and promotors
 

domain boundaries (insulator elements)
 

C. The concept of self-perpetuating clonally inherited chromosome structure
 

Extreme examples are imprinting and X-inactivation
 
 
 

X-inactivation:
 

http://www.ultranet.com/~jkimball/BiologyPages/S/SexChromosomes.html#x-inactivation
 
 
 

Imprinting
 

http://www.ultranet.com/~jkimball/BiologyPages/I/Imprinting.html