Lecture 12

Question 1

In _______ state:
Transcription factors and RNA polymerase can access the regulatory regions and
transcribe the gene

Answer 1

euchromatin

Question 2

In _________ state:
Transcription factors and RNA polymerase are unable to access the regulatory
regions and transcribe the gene

Answer 2

heterochromatin

Question 3

_________ – causing phenotypic changes by modifying how a gene is expressed,
rather than modifying the DNA sequence itself

Answer 3

Epigenetics

Question 4

epigentic control alters __________

Answer 4

chromatin accessibility

Question 5

what are the two ways epigentic modification can modulate access to genes?

Answer 5

modifications to histones
modifications to DNA

Question 6

histone modification (epigenetics): ____________

Answer 6

Control gene expression by modifying histone tails

Question 7

_________ add acetyl
groups to histone tails

Answer 7

Histone acetyltransferases

Question 8

how does Histone acetyltransferases change the chromatin state? to which kind does it change to?

Answer 8

destabilizes the tight
packaging of nucleosomes, leading to a
more euchromatic chromatin state

Question 9

Histone methylation involves adding methyl groups to histone tails by __________

Answer 9

histone methyltransferases

Question 10

where does DNA methylation occur?

Answer 10

on cytosine bases

Question 11

why does the covalent addition of methyl groups
generally turn off transcription?

Answer 11

blocks proteins from accessing the DNA sequence they need

Question 12

true/false: Epigenetic modifications are heritable

Answer 12

true! The epigenetic modifications on the parent DNA strand can be copied to the daughter DNA strand
as it is synthesized

Question 13

true/false: Environmental factors can influence epigenetic modifications -diet, stress, and exposure to toxins

Answer 13

true

Question 14

which organ is most sensitive to epigenetic changes?

Answer 14

the brain

Question 15

how do we generate different cell types?

Answer 15

A transcription regulator switches on its own gene
and other genes unique to the cell type

(Combinations of just a few transcription
regulators can give rise to numerous cell
types during development)

Question 16

Regulatory ___ control the expression of
thousands of genes

Answer 16

RNAs

Question 17

________ direct the destruction of target mRNAs

Answer 17

MicroRNAs

Question 18

The mature miRNA (~22 nucleotides) is packaged with specialized proteins to form
an ________

Answer 18

RNA-induced silencing complex (RISC)

Question 19

Once base pairing with a complementary mRNA sequence is established, a ___
in the RISC complex degrades the mRNA

Answer 19

nuclease

Question 20

what kind of match do you need to rapidly degrade an mRNA with the nuclease in the RISC?

Answer 20

an extensive match

Question 21

what kind of match do you need to eventually (slowly) degrade an mRNA with nucleases in the cytosol?

Answer 21

a less extensive match, partial match

Question 22

_______: Protect cells from infections

Answer 22

small interfering RNAs, siRNA

Question 23

Long double-stranded RNA is rarely produced by normal
genes; instead, it is typically intermediates in the life cycles
of _______

Answer 23

viruses

Question 24

siRNAs are used in cells to…

Answer 24

Infected cell effectively turns the foreign RNA against itself

Question 25

how do siRNA’s turn against its own foreign RNA?

Answer 25

One strand is loaded onto the RISC complex, which destroys
complementary RNA molecules