Class 11: Gene Expression

Question 1

Bacteria use ____ as their source for carbon, but when that is scarce they can use ____ as their source of carbon

Answer 1

glucose, lactose

Question 2

what elements regulate the lactose operon of E. Coli

Answer 2

1) operator: suppressed by Lac repressor (default). The repressor inhibits transcription by binding to the lac operator (O). Repressor binding to the operator is prevented by the inducer.

2) CAP binding site: activated by catabolite activator protein (CAP), which stimulates the transcription of lactose gene when bound to cAMP.

Question 3

Adenylyl cyclase is inhibited by ____ and no ____ is made

Answer 3

glucose, cAMP

Question 4

+Glucose, -LActose

Answer 4

operon off
-adenylyl cyclase is inactive, transcription is blocked, no mRNA thus nor proteins made

Question 5

-Glucose, +Lactose

Answer 5

Operon on
-adenylyl is active
-operator is not blocked, RNA polymerase starts transcription
-allolactose binds to repressor protein, causing a conformation change that prevents its binding to the inhibitor

Question 6

+Glucose, +Lactose

Answer 6

Operon off
- adenylyl is inactive bc of presence of glucose
- CAP binding site is empty do no RNA polymerase for transcription
- few molecules of premise and allolactose is formed

Question 7

-Glucose, -lactose

Answer 7

operon off
- transcription is blocked
- no mRNA thus no protein

Question 8

Transcription factors

Answer 8

are proteins that bind to specific DNA sequences and control the transcription of genetic information from DNA to RNA

Question 9

Cis-acting elements

Answer 9

are DNA sequences that regulate the expression of a gene located on the same molecule of DNA

Question 10

Tans-acting elements

Answer 10

are proteins that recognize cis-acting elements and regulate RNA synthesis. They are commonly called transcription factors.

Question 11

Gene expression is regulated by

Answer 11

hormones

Question 12

liquid soluble hormones

Answer 12

can go through the plasma membrane and go into cells

• hydrophobic signal molecules

Question 13

water soluble molecules

Answer 13

they deliver signals outside the cell

Question 14

transcription by lipid soluble hormone receptors

Answer 14

1) They can go through the plasma membrane and go into the cells.

2) They bind to hormone receptors and go directly into the nucleus.

3) Hormone receptors bind to specific regions of the DNA called hormone response elements (HRE)) and activate gene expression.

4) Nuclear hormone receptors are transcription factors.

5) Nuclear hormone receptors have two highly conserved domains: 1) The DNA binding domain and 2) the ligand binding domain.

Question 15

tamoxifen

Answer 15

antagonist of estrogen receptor, competitively binds to receptor, anti-breast cancer drug

Question 16

antagonist to the estrogen receptor are called

Answer 16

elective estrogen receptors modulators

Question 17

first messenger in water soluble hormones

Answer 17

Insulin, Epinephrine, Glucagon (water soluble Hormones)

Question 18

second messenger in water soluble hormones

Answer 18

cAMP, cGMP, calcium

Question 19

alternative splicing

Answer 19

the process of selecting different combinations of splice sites within a messenger RNA precursor (pre-mRNA) to produce variably spliced mRNAs

Question 20

alternative splicing increases the _____ and _____ of an orgasm

Answer 20

functional diversity, complexity

Question 21

Transferrin receptor (TfR)

Answer 21

is a carrier protein for transferrin. It is needed for the import of iron into the cell and is regulated in response to intracellular iron concentration. It imports iron by internalizing the transferrin-iron complex through receptor-mediated endocytosis.

Question 22

Ferritin

Answer 22

is a protein that stores iron, releasing it when the body needs it.

Question 23

Production of the transferrin receptor (TfR) and ferritin is regulated at the
level of mRNA by iron regulatory proteins (IRPs), which bind to
iron response elements (IREs) on the 3’- (TfR) and 5’- (ferritin)
untranslated regions of their respective mRNAs.

Answer 23

• • Binding of IRPs to the IRE of TfR on the 3’ end of mRNA stabilizes the mRNA, facilitating the translation.

-Binding of IRPs to the IRE of ferritin on the 5’ end of mRNA inhibits the translation.

Question 24

Production of the transferrin receptor (TfR) and ferritin is regulated at the level of mRNA by ____, which bind to
_____ on the 3’- (TfR) and 5’- (ferritin)
untranslated regions of their respective mRNAs.

Answer 24

iron regulatory proteins (IRPs),

iron response elements (IREs)

Question 25

Epigenetics

Answer 25

is the study of heritable changes
in gene expression (active versus inactive
genes) that does not involve changes to the
underlying DNA sequence — a change in phenotype without a
change in genotype — which in turn affects how cells read the genes.

Question 26

DNA does not normally exist as the simple double helix described in the module on DNA structure. Instead, eukaryotic DNA is found packaged with protein, forming a substance called

Answer 26

chromatin

Question 27

Modification of the ____ tails of the histones alters chromatin accessibility and gene expression.

Answer 27

N-terminal tails

Question 28

Chemical ____ of chromatin influences both chromatin structure and gene expression

Answer 28

modifications to DNA

Question 29

histone code hypothesis

Answer 29

proposes that specific combinations of modifications, as well as the order in which they occur, help determine chromatin configuration and influence transcription.

Question 30

Inactivation of Tumor suppressor:

Answer 30

meCpG to TpG mutation: account for 1/3 of transition mutation in human. more than 50% of all of the p53 mutations which are acquired in sporadic colorectal cancer occurs at sites of cytosine methylation