Chapter 7.5

Question 1

What is the purpose of transcription factors?

Answer 1

• their purpose is to search for DNA

- >and bind to specific DNA motifs

Question 2

What are the two domains of transcription factors

Answer 2

1) DNA-binding domain
- >binds to a specific nucleotide sequence in the promoter region or to a DNA response element

2) Activation domain
- >allows for the binding of several transcription factors and other regulatory proteins(RNA polymerase)

Question 3

What is meant by the term response element

Answer 3

• sequence of DNA

- >that binds only to specific transcription factors

Question 4

What is an enhancer?

Answer 4

• an enhancer is several response elements grouped together

- >it allows for control of one gene’s expression by multiple signals

Question 5

What is the purpose of histone acetylation. What is the purpose of histone deacetylation

Answer 5

• they acetylate lysine residues found in the amino terminal tail regions of histone proteins
• > acetylation decreases the positive charge on the lysine residues
• > weakens the interaction of histone with DNA
• > results in open chromatin conformation that allows for reasier access of the transcriptional machinery to the DNA

-note histone deacetylation causes gene silencing

Question 6

What does DNA methylase do? What does this result in?

Answer 6

• DNA methylases add methyl groups to cytosine and adenine nucleotides
• > methylation of the genes is often linked with the silencing of gene expression

-note heterochromatin regions of DNA are more likely to be methylated