All microtubules are nucleated from structures known as microtubule-organizing centers, or MTOCs.

 

TLS Online TPP Program

#Id: 6862

#Unit 3. Fundamental Processes

Some of the regions in the eye lack color, whereas others are red. This is because the white gene (required to develop red pigment) was inactivated by adjacent heterochromatin in some cells, but remained active in others.

TLS Online TPP Program

#Id: 6863

#Unit 3. Fundamental Processes

Su(var) for genes

whose products act to suppress variegation and E(var) for genes whose products enhance variegation.

active in others.

TLS Online TPP Program

#Id: 6864

#Unit 3. Fundamental Processes

Su(var) mutations lie in genes whose products are needed for the formation of heterochromatin such as HDAC, HMT.

TLS Online TPP Program

#Id: 6865

#Unit 3. Fundamental Processes

E(var) mutations lie in genes whose products are needed to activate gene expression. They include members of the SWI/SNF complex

TLS Online TPP Program

#Id: 6866

#Unit 3. Fundamental Processes

HP1 (heterochromatin protein 1) is one of the most important Su(var) proteins. The HP1 chromodomain binds to histone H3 that is trimethylated at lysine 9 (H3K9me3).

TLS Online TPP Program

#Id: 6867

#Unit 3. Fundamental Processes

Mutation of a deacetylase that acts on H3K14Ac prevents the methylation at K9 because HDAC provide methylation sites for HMT.