6.5: Regulation of Gene Expression

Question 1

What are regulatory sequences?

Answer 1

Stretches of DNA that can be used to promote or inhibit protein synthesis.

Question 2

What is the promoter region?

Answer 2

Where the transcription initiates, usually before the operator.

Question 3

What is the TATA box?

Answer 3

The section of the promoter that the transcription factors bind to and allow the process of transcription to start.

Question 4

What is the enhancer region?

Answer 4

This is bound to the promoter region by transcription factors, which act as more controls.

Question 5

How is DNA modified to initiate transcription (to regulate gene expression)?

Answer 5

Euchromatin is more likely to be expressed.

Question 6

How is DNA modified to inhibit transcription (to regulate gene expression)?

Answer 6

Methylated DNA or heterochromatin (mostly on cytosine) causes less expression of those genes.

Question 7

How are histones modified to initiate transcription (to regulate gene expression)?

Answer 7

Histones loosely packing DNA can allow the process of DNA synthesis. (histone acetylation)

Question 8

True or False: All somatic cells have the same DNA.

Answer 8

True

Question 9

What is cell differentiation?

Answer 9

Cells differentiate into different tissues that have specialized functions due to changes in gene expression.

Question 10

Why can different phenotypes result from different levels of gene expression?

Answer 10

The combination of genes that are expressed.

Question 11

What is the function of transcription factors?

Answer 11

proteins that promote or inhibit transcription factors of a gene, which determine how the cell differentiates.

Question 12

What is an operon?

Answer 12

Closely linked genes that produce a single mRNA molecule during transcription. (the gene, regulatory sequence, and operator).

Question 13

Describe the lac operon. What happens when lactose is present? What happens when lactose is absent? Is this operon repressible or inducible?

Answer 13

It is inducible because it is usually turned off.

Question 14

What is an operator?

Answer 14

The operator inhibits or promotes transcription by binding with regulatory proteins.

Question 15

What is a repressor?

Answer 15

It attaches to the operator to inhibit the operon from expressing the gene.

Question 16

What is a promoter?

Answer 16

h

Question 17

How does the repressor interact with the promoter?

Answer 17

h

Question 18

Describe the lac operon. What happens when lactose is present? What happens when lactose is absent? Is this operon repressible or inducible?

Answer 18

It is inducible because it is usually turned off. When lactose is present, the repressor is inhibited and the operon is translated, resulting in the break down of lactose into glucose. When the lactose is not present, the operon is turned off and lactose is not broken down. When glucose is low, then the promoters increase

Question 19

Describe the trp operon. What happens when tryptophan is present? What happens when tryptophan is absent? Is this operon repressible or inducible?

Answer 19

This is a repressible operon, which means it is usually on. When tryptophan is present, then it binds to the repressor and initiates the binding of the repressor to the operator. When the operon is inhibited, the mRNA coding for additional tryptophan is inhibited.