lecture 15

Question 1

housekeeping genes

Answer 1

genes that are common to all cells

ex. ribosomal proteins, RNA polymerases..

Question 2

if you inject cortisol into a liver cell, fat cell and another cell, what will happen?

Answer 2

they won’t respond in the same way

Question 3

regulation of gene expression is important in step..

Answer 3

1!! very important for control over transcription at step 1

but regulation can occur at various steps

Question 4

regulatory DNA sequences turns

Answer 4

DNA “on” or “off”

Question 5

give an example (trp operon) of a regulatory DNA sequence

Answer 5

the operator trp operon is a regulatory DNA sequence that controls transcription of the trypothan production-related products by being bound to a repressor protein

Question 6

transcription regulators bind to

Answer 6

regulatory DNA sequences

Question 7

transcriptional regulator (tryptophan example)

Answer 7

the tryptophan repressor is a transcription regulator

it is a transcriptional REPRESSOR specifically because it inhibits transcription

Question 8

Transcription regulators can also promote…

Answer 8

gene expression

Question 9

example of a transcriptional activator

Answer 9

CAP is a transcriptional activator bc it binds to regulatory DNA sequences which promotes gene expression

Question 10

in bacteria, genes that encode proteins that are involved in the same process are often clustered in

Answer 10

operons!!

controlled by a single promoter

Question 11

Lac operon has multiple

Answer 11

transcription regulators

Question 12

when lactose is present, the lac repressor

Answer 12

does not bind to the operator

Question 13

when lactose is absent, the lac repressor

Answer 13

binds to the operator and prevents transcription

Question 14

what is produced when lactose is present

Answer 14

allolactose

Question 15

CAP is a

Answer 15

transcriptional activator

binds to regulatory sequences to promote transcription of the lac operon

Question 16

explain positive regulation of Lac operon (CAP)

Answer 16

CAP helps the RNA polymerase bind

CAP only binds when there are high levels of cyclic AMP (cAMP)

Question 17

levels of cAMP are inversely proportional to levels of

Answer 17

glucose

Question 18

enhancer

Answer 18

binding site for activator proteins

promotes transcription

Question 19

repressors do the opposite of

Answer 19

enhancers

Question 20

mediator

Answer 20

complexes of proteins that are an intermediate between regulatory proteins and the transcription complex

Question 21

eukaryotes need to deal with

Answer 21

higher levels of chromatin condensation

Question 22

eukaryotes and chromatin-modifying proteins

Answer 22

1. chromatin-remodeling complexes
2. covalently modify the histone proteins

Question 23

give an example of a chromatin-modifying protein

Answer 23

Histone acetyltransferases promote the acetylation of lysine, allows greater accessibility of the DNA

Histone deacetylases remove the acetyl groups to reverse this effect

Question 24

cell memory

Answer 24

changes in gene expression are remembered by a cell

Question 25

combinatorial control is

Answer 25

the way groups of transcription regulators work together
- many genes are controlled by dozens of regulators

Question 26

do eukaryotes cluster genes into operons?

Answer 26

no!
only bacteria do this

Question 27

eukaryotes use combinatorial control to make

Answer 27

a single transcription regulator to control multiple genes at the same time

Question 28

combinatorial control– lock example

Answer 28

when the triangle is present (transcription activator), all three genes can be expressed at the same time

Question 29

3 epigenetic mechanisms behind cell memory

Answer 29

1. positive feedback loops
2. DNA methylation
3. histone modifications

Question 30

how do the 3 epigenetic mechanisms work?

Answer 30

they alter gene expression WITHOUT altering the nucleotide sequence of the DNA

they are forms of epigenetic inheritance

Question 31

positive feedback loops

Answer 31

transcription regulator that causes a cell to differentiate into a particular cell type activates transcription of itself,
this ensures that all future
progeny will also be of the same type

Question 32

DNA methylation

Answer 32

can affect gene expression

patterns are passed down to progeny cells

Question 33

Histone modifications

Answer 33

can affect gene expression (histone code!!)

the modifications can be inherited by daughter chromosomes

Question 34

regulatory RNAs are

Answer 34

noncoding RNAs that can regulate gene expression

Question 35

3 regulatory RNAs

Answer 35

miRNAs (micro)
siRNAs (small interfering)
long noncoding RNAs

Question 36

long noncoding RNAs can work in 2 ways

Answer 36

1. coat the chromosome, causes association of chromatin-remodeling complexes to form heterochromatin
2. transribed from the “wrong” DNA strand which bind to the mRNA transcript

Question 37

RISC

Answer 37

RNA-inducing silencing complex

Question 38

miRNA– how does it cause degradation of mRNA?

Answer 38

miRNA binds to complementary sequences on target mRNA and causes degradation of that mRNA by nucleases in the RISC

Question 39

siRNAs acts as a

Answer 39

defense against foreign RNA
- system known as RNA interference

Question 40

how do siRNAs degrade mRNA?

Answer 40

siRNAs bind to RISC
the bound RNA binds to complementary RNA which causes its degradation by nucleases in the RISC

Question 41

how are siRNAs formed?

Answer 41

foreign dsRNA is cleaved by a dicer (protein) which results in siRNAs