CHAPTER 15

Question 1

What are transcription factors?

Answer 1

Transcription factors are proteins that influence RNA polymerase’s ability to transcribe a gene.

Question 2

Two main types of transcription factors

Answer 2

1. General transcription factors
2. Regulatory transcription factors

Question 3

General transcription factors

Answer 3

required for the binding of RNA polymerase to the core promoter and for basal transcription.

Question 4

Regulatory transcription factors

Answer 4

regulate the transcription rate of target genes and influence RNA polymerase’s ability to begin transcription.

Question 5

What are control elements in gene regulation?

Answer 5

Control elements, also known as cis regulatory elements, are sequences located near the core promoter.

Question 6

How are control elements recognized?

Answer 6

They are recognized by regulatory transcription factors, which can either increase (activators) or decrease (repressors) the rate of transcription.

Question 7

What roles do activators and repressors play in transcription?

Answer 7

-Activators: Proteins that increase transcription rates by binding to enhancers.
-Repressors: Proteins that decrease transcription rates by binding to silencers.

Question 8

What is combinatorial control in gene regulation?

Answer 8

Combinatorial control refers to the regulation of most eukaryotic genes by multiple factors.

Question 9

What does combinatorial control in gene regulation include?

Answer 9

1. One or more activators stimulate transcription.
2. One or more repressors inhibiting transcription.
3. Modulation by small effector molecules, protein-protein interactions, or covalent modifications.

Question 10

What are domains in transcription factors?

Answer 10

Domains are regions of transcription factor proteins with specific functions (e.g., DNA-binding, binding sites for effector molecules).

Question 11

What are motifs in transcription factors?

Answer 11

A motif is a domain or part of a domain that has a similar structure across various proteins.

Question 12

Enhancers

Answer 12

Binding of a transcription factor increases transcription rates (up-regulation).

Question 13

Silencers

Answer 13

Binding of a transcription factor decreases transcription rates (down-regulation).

Question 14

Mediator

Answer 14

A complex that interacts with transcription factors and RNA polymerase, facilitating transcription activation and repression.

Question 15

TFIID

Answer 15

A general transcription factor that recruits RNA polymerase to the core promoter.

Question 16

What are the three common ways to modulate the function of regulatory transcription factors?

Answer 16

1. Binding of small effector molecules.
2. Protein-protein interactions.
3. Covalent modifications.

Question 17

How do steroid hormones affect regulatory transcription factors?

Answer 17

Steroid hormones bind directly to their receptors, affecting gene transcription.

Question 18

How does chromatin structure impact gene expression?

Answer 18

-Chromatin can exist in closed (tightly packed, inhibiting transcription)
-Open (accessible to transcription factors, allowing transcription) conformations
-Directly influencing the ability to express genes.

Question 19

How do chromatin remodeling complexes alter gene expression?

Answer 19

They change nucleosome positions and compositions using ATP hydrolysis, making DNA more or less accessible for transcription.

Question 20

What is DNA methylation and its effect on gene transcription?

Answer 20

DNA methylation is the covalent addition of methyl groups, usually inhibiting eukaryotic gene transcription. It is performed by DNA methyltransferases.

Question 21

What are CpG islands and their role in gene regulation?

Answer 21

CpG islands are regions near gene promoters with high frequencies of CpG sites.
-In housekeeping genes, they are generally unmethylated, leading to expression,
-Tissue-specific genes, methylation can silence their expression.

Question 22

What mechanisms regulate translation after mRNA synthesis?

Answer 22

-RNA-binding proteins that affect translation and degradation of mRNAs.
-Small RNAs (covered in Chapter 17).
-Iron Response Protein (IRP) illustrate these mechanisms.

Question 23

How does the Iron Regulatory Protein (IRP) regulate iron uptake?

Answer 23

IRP binds to Iron Response Elements (IREs) in mRNAs for ferritin and transferrin receptor.

Question 24

Low Iron

Answer 24

IRP binds to IRE, preventing ferritin translation.

Question 25

High Iron

Answer 25

Iron binds to IRP, allowing ferritin translation and degradation of transferrin receptor mRNA.