Chapter 18

Question 1

Even though human cells share the same genome, why do they look and function differently from one another?

Answer 1

Because each type of cell expresses different sets of genes.

Question 2

Where can gene regulation take place?

Answer 2

• through chemical modification of chromatin or histones
• during transcription
• during RNA processing
• during translation

Question 3

what is gene regulation?

Answer 3

Gene regulation is the process of controlling which genes in a cell’s DNA are expressed (used to make a functional product such as a protein).

Question 4

what can alter gene expression?

Answer 4

nucleosomes

Question 5

what is chromatin and function in gene regulation

Answer 5

a coiled complex of DNA, RNA, and proteins that gives chromosomes their structure.

Chromatin must unravel to allow space for transcription

Coiling is facilitated by histone complexes called
nucleosomes

DNA coiled around the nucleosome is inaccessible for
transcription (genes are ‘silenced’)

Question 6

what is chromatin remodelling?

Answer 6

nucleosomes are repositioned to expose different stretches of DNA.

Question 7

what is Methylation?

Answer 7

addition of a methyl group to cytosine bases adjacent to
guanosine bases on a DNA strand (CpG)

Question 8

Use of methylation

Answer 8

Methylation is a way to turn genes on or off

Heavy methylation leads to gene repression

Question 9

what is epigenetic effects?

Answer 9

alterations that affect how DNA expressed (rather than to the DNA sequence itself)

Question 10

what does Methylation or Histone modification do?

Answer 10

These changes sometimes cause changes in gene expression.

They can be inherited but are often reversible and responsive to changes in the environment.

Question 11

How is high vs. low licking is ‘inherited’ epigenetically

Answer 11

Mothers lick their newborn offspring

Offspring of ‘high licking’ (i.e. good) mothers are good
mothers themselves

Question 12

what is dosage compensation?

Answer 12

Sex-specific regulation of X chromosome

Question 13

Inactivation of one X chromosome in females is called

Answer 13

X inactivation

Question 14

Explain X inactivation

Answer 14

Question 15

How does transcription factors regulate gene expresion?

Answer 15

•Transcription factors regulate gene expression
•Enhancers bind at enhancer sequences near the
promotor region
•Recruit RNA polymerase complex
•Silencers bind and repress transcription

Question 16

How does RNA processing helps with gene regulation

Answer 16

RNA splicing provides an opportunity for regulating gene expression.

Question 17

what is alternative splicing?

Answer 17

The same primary transcript can be spliced in different ways to yield different proteins, a phenomenon called alternative splicing

Question 18

Hows does small regulatory RNA regulate expression?

Answer 18

•Binding to transcripts and blocking
translation
•Blinding to transcripts causing degradation

Question 19

what RNA folds back on itself to form a hairpin?

Answer 19

microRNAs and small interfering RNAs (siRNA)

Question 20

Function of Post-translational modifications

Answer 20

serve to regulate structure and function of proteins
•Regulates protein activity
•e.g. phosphorylation

Question 21

The lac operon image

Answer 21

Question 22

Lac operon is a controlled cascade

Answer 22

Mutations & the lac operon