Control of Gene Expression in Eukaryotes

Question 1

Transcription factors

Answer 1

search for promoter and enhancer regions in the DNA

Question 2

Promotes

Answer 2

are within 25 basepairs of the transcription start site

Question 3

Enhancers

Answer 3

are more than 25 base pairs away from the transcription start site.
allows for the control of one gene’s expression by multiple signals

Question 4

Modification of chromatin structure affects

Answer 4

the ability of transcriptional enzymes to access the DNA through histone acetylation (increases accessibility) or DNA methylation (decreases accessibility).

Question 5

2 domains in Transcription factors

Answer 5

DNA binding domain

activation domain

Question 6

DNA binding domain

Answer 6

binds to a specific nucleotide sequence in the promoter region or to a DNA response element (a sequence of DNA that binds only to specific transcription factors) to help in the recruitment of transcriptional machinery.

Question 7

Activation domain

Answer 7

allows for the binding of several transcription factors and other important regulatory proteins, such as RNA polymerase and histone acetylates, which function in the remodeling of the chromatin structure

Question 8

The large distance between the enhancer and promoter regions for a given gene means

Answer 8

that DNA often must bend into a hairpin loop to bring these elements together spatially

Question 9

Heterochromatin

Answer 9

tightly coiled DNA that appears dark under the microscope; its tight coiling makes it inaccessible to the transcription machinery, so these genes are inactive

Question 10

Euchromatin

Answer 10

looser than heterochromatin and appears light under the microscope; the transcription machinery can access the genes of interest, so these genes are active.

Question 11

Remodeling of the chromatin structures

Answer 11

regulates gene expression levels in the cell

Question 12

Histone acetylases

Answer 12

proteins involved in chromatin remodeling because they acetylate lysine residues found in the amino terminal tail regions of histone proteins.

Specific patterns of this can lead to increased gene expression levels.

Question 13

Acetylation of histone proteins

Answer 13

decrease the positive charge on lysine residues and weakens the interaction of the histone with DNA, resulting in an open chromatin conformation that allows for easier access of the transcriptional machinery to the DNA

Question 14

Histone deacetyleases

Answer 14

proteins that function to remove acetyl groups from histones, which results in a closed chromatin conformation and overall decrease in gene expression levels in the cell

Question 15

DNA methylation

Answer 15

involved in chromatin remodeling and regulation of gene expression levels in the cell.

Question 16

DNA methylases

Answer 16

add methyl groups to cytosine and adenine nucleotides; methylation of gene is often linked with the silencing of gene expression.
During development, DNA methylases play an important role in silencing genes that no longer need to be activated.