Chapter 19: Control of Gene Expression in Eukaryotes

Question 1

What is differential gene expression?

Answer 1

cells with the same genome express different sets of genes

Question 2

What does differential gene expression do?

Answer 2

• creates different cell types
• arranges cells into tissues
• coordinates activity

Question 3

What are the four additional levels of gene regulation in eukaryotes?

Answer 3

1. chromatin remodeling
2. RNA processing
3. mRNA stability
4. protein degradation

Question 4

What is chromatin remodeling?

Answer 4

genes must be made accessible

Question 5

What is RNA processing?

Answer 5

splicing can create different combos of exons

Question 6

What is protein degradation?

Answer 6

proteins can be marked and destroyed

Question 7

What is mRNA stability?

Answer 7

mRNAs can be blocked or degraded

Question 8

Describe histones.

Answer 8

DNA wrapped around proteins called histones

Question 9

What is a nucleosome?

Answer 9

DNA + histones

Question 10

What are the 3 ways chromatin is altered during gene expression?

Answer 10

1. DNA methylation
   2.Histone acetylation
2. chromatin-remodeling complexes

Question 11

What is DNA methylation?

Answer 11

• methyl groups (CH3) added to C nucleotides
• catalyzed by DNA methyltransferases

Question 12

What does methylation do?

Answer 12

• condenses chromatin
• low methylation near promoter: increase transcription and vice versa

Question 13

What is histone acetylation?

Answer 13

• acetyl groups are added to lysine on histone tails

Question 14

What are histone acetyltransferases?

Answer 14

• HATs
• add acetyl groups, open DNA

Question 15

What are histone deacetylases?

Answer 15

-HDACs
- remove acetyl groups, close DNA

Question 16

Acetylation leads to ________ chromatin.

Answer 16

decondensed

Question 17

What are chromatin remodeling complexes?

Answer 17

• large enzyme complex that uses ATP to reshape chromatin
• slide nucleosomes, or knock histones off the DNA

Question 18

What are epigenetics?

Answer 18

any mechanism of inheritance due to something other than changes in DNA sequence

Question 19

What are the 2 major implications of epigenetics?

Answer 19

1. epigenetic patterns can be passed to offspring
2. epigenetic patterns can be altered by environment

Question 20

What is the core promoter?

Answer 20

binding site for RNA polymerase

Question 21

Describe promoter proximal elements.

Answer 21

close to promoter, allow coordinated regulation of genes of the same type

Question 22

Describe enhancers.

Answer 22

far from the promoter, bound by an activator to begin and increase transcription

Question 23

Describe silencers.

Answer 23

far from the promoter, bound by repressors and shut down transcription

Question 24

Describe general transcription factors.

Answer 24

1. bind to core promoter to initiate transcription in many genes
2. not involved in much regulation

Question 25

Describe regulatory transcription factors.

Answer 25

1. bind to enhancers, silencers, promoter-proximal elements 2. specific for dif types of cells

Question 26

What are the 4 steps of transcription initiation?

Answer 26

1. chromatin remodeling 2. exposure of promoter and regulatory sequences 3. assembly of proteins 4. RNA polymerase binds to core promoter

Question 27

What is chromatin remodeling?

Answer 27

- transcriptional activators bind to enhancers, recruit chromatin remodeling complexes or HATs

Question 28

What is exposure of promoter and regulatory sequences?

Answer 28

- a region of DNA is exposed, including the promoter, promoter-proximal element, and other enhancers

Question 29

What are assembly of proteins?

Answer 29

- other transcriptional activators bind to exposed DNA - DNA is looped and activators bind to mediator

Question 30

What is RNA polymerase binds to core promoter?

Answer 30

- GTFs and RNAP assemble on mediator, RNAP binds to promoter and transcription begins

Question 31

What is alternative splicing?

Answer 31

the same primary transcript (pre-mRNA) can be spliced in different ways (same gene can yield more than one mature mRNA)

Question 32

What is RNA interference?

Answer 32

short single stranded RNAs work w/ a protein complex to bind to mRNAs to cause either... 1. degradation of the mRNA 2. block mRNAs from translation

Question 33

What are the 3 RNA interference molecules?

Answer 33

- microRNAs - short interfering RNAs - PIWI-interacting RNAs

Question 34

What are the steps of miRNA production?

Answer 34

1. transcription by RNA polymerase II (forms hairpin) 2. processed and exported from nucleus by special protein complexes 3. bound by RISC and unwound into single strand 4. RISC + mRNA base pairs to mRNA (perfect match=mRNA destroyed, imperfect match=prevent translation)

Question 35

What does ubiquitin do?

Answer 35

small proteins that are added to a protein to degrade them

Question 36

What does the proteasome do?

Answer 36

large complexes that break down ubiquitinated proteins