8/20/14 - Gene Expression II

Question 1

How does the locus control region (LCR) affect beta-globin gene expression in immature RBCs?

Answer 1

-Transcription factors bind to LCR region of beta-globin gene -Induce formation of euchromatin downstream in coding region where a cluster of globin genes is located -Euchromatin formation promotes transcription of globin gene expression

Question 2

When a cell prepares to differentiate, what combination of transcription factors would be expressed to facilitate that process?

Answer 2

Mad/Max heterodimer

Question 3

How many genes in sperm and egg cells are known to maintain methylation?

Answer 3

50 total, 25 different genes in each

Question 4

Describe the general process of signal transduction

Answer 4

A cascade of chemical reactions initiated by an extracellular signal that generally modifies levels of transcription on a gene or set of genes.

Question 4

How is the extra X-chromosome in females inactivated?

Answer 4

A random x-chromosome is signaled for inactivation early during embryogenesis by promoting the formation of heterochromatin.

Question 4

What are epigenetic traits?

Answer 4

Inherited traits not caused by changes in DNA sequence.

Question 6

How do CpG islands influence gene transcription?

Answer 6

Prevents methylation of promoters, promotes gene transcription

Question 7

In what class of genes are you most likely to find CpG islands?

Answer 7

Housekeeping gene promoters

Question 8

Myc, Max, and Mad bind to genes that regulate which cellular process?

Answer 8

Cell division

Question 8

Compare which regions of the beta-globin gene would be expressed in normal 1) adults 2) children following LCR activation

Answer 8

1) beta chain gene expressed 2) gamma chain gene expressed

Question 9

Myc, Max, and Mad share which structural element? (draw)

Answer 9

Helix-Loop-Helix

Question 9

When a cell prepares to divide, what combination of transcription factors would be expressed to facilitate that process?

Answer 9

Myc/Max heterodimer

Question 9

How is DNA methylation inherited?

Answer 9

A maintenance methyltransferase methylates newly synthesized DNA strands at hemi-methyl sites.

Question 10

What effect does the Myc/Max heterodimer have on gene transcription?

Answer 10

Gene activation

Question 12

What effect does the Max/Max homodimer have on gene transcription?

Answer 12

Gene silencing

Question 14

List the steps by which positive feedback transcription factor loops generate cellular memory? (draw)

Answer 14

-Protein A is not normally expressed because it acts as its own transcription factor. -Transient signal activates gene for protein A. -Protein A then upregulates its own expression. -The high concentration of protein A can be inherited and maintained through many generations to maintain high levels of expression.

Question 15

Which nucleotide is a target for DNA methylation?

Answer 15

Cytosine, but only if followed directly by a guanine.

Question 16

Which transcription factors increase AP-1 expression?

Answer 16

Jun, Fos

Question 18

What class of kinase enzyme activates Jun?

Answer 18

JNK

Question 19

When the concentration of Mad and Max transcription factors are high in a cell, what process is most likely occurring?

Answer 19

Cell differentiation

Question 20

When the concentration of the Max transcription factor is high in a cell, what process is most likely occurring?

Answer 20

Basal transcription

Question 21

When the concentrations of Myc and Max transcription factors are high in a cell, what process is most likely occurring?

Answer 21

Cell division

Question 22

How are most genes in sperm and egg cells stripped of methyl groups?

Answer 22

Exact mechanism unknown, but methylation marks are removed to promote gene activation.

Question 23

How are the Jun/Fos transcription factors activated?

Answer 23

Phosphorylation

Question 25

How are acetylated histone regions passed from generation to generation?

Answer 25

A maintenance acetyltransferase acetylates nucleosomes in areas of hemi-acetylation

Question 26

What class of enzyme catalyzes phosphorylation?

Answer 26

Kinases

Question 27

Discuss how positive feedback transcription factor loops are the key to cellular differentiation. (draw)

Answer 27

-Positive TF feedback loop generates a variety of cell types, each of which has a unique signature of active TFs. -The combination of active TFs determines the overall level of gene expression in the cell.

Question 28

Describe the characteristics and mechanism of action for the Max transcription factor.

Answer 28

-Constitutive expression -Forms homodimers, binds to E-box promoter element -Max homodimer reduces gene expression

Question 29

How does the position of a gene in a chromosome influence gene transcription?

Answer 29

Genes in heterochromatin are usually silenced.

Question 30

How might genomic imprinting occur in a sex-dependent manner? (draw)

Answer 30

-A particular allele retains its methylation in either the sperm or the egg, but not both.

Question 31

What effect does the Mad/Max heterodimer have on gene transcription?

Answer 31

Gene repression

Question 32

How does methylation of DNA at the promoter region influence gene transcription?

Answer 32

Usually inhibits gene expression.

Question 33

What class of kinase enzyme activates Fos?

Answer 33

ERK