gene expression regulation

Question 1

central dogma

Answer 1

the concept that cells follow a particular direction/flow of genetic information

genes provide the information for making proteins —> genes move from DNA —> RNA —> proteins

transcription makes pre-mrna/mrna
translation —> creates polypeptide genes (proteins)

Question 2

difference between transcription and translation in prokaryotes and eukaryotes

Answer 2

location that they occur

prokaryotes—> cytoplasm bc they don’t have a nucleus

eukaryotes—> transcription occurs in nucleus and translation occurs in the cytoplasm

Question 3

nearly all cells in your body have the same DNA.. how

Answer 3

we start from a single cell, and DNA from that cell gets copied every time we make a new cell

Question 4

how can two cells with the same set of genes function differently

Answer 4

gene regulation

Question 5

gene regulation

Answer 5

process of turning on/off different genes when they are needed

— occurs due to both internal and external environment of the cell

Question 6

where does most gene regulation occur in prokaryotes and eukaryotes

Answer 6

happens in transcription

however for eukaryotes gene regulation occurs in many other steps as well

Question 7

differential gene expression

Answer 7

allows certain cells to be or to not be expressed based on needs

Question 8

transcription factors

Answer 8

proteins that bind to dna sequence and initiate transcription

Question 9

rna polymerase II

Answer 9

protein that pulls apart 2 dna strands and joins RNA nucleotides complementary to the dna template strand

Question 10

transcription regulation involves transcription factors that exert negative or positive control

what are two types of transcription factors

Answer 10

repressor protein
activator protein

Question 11

repressor protein

Answer 11

binds to dna and decreases(or inhibits) the rate of transcription

negative control

Question 12

activator protein

Answer 12

binds to dna and increases the rate of transcription

positive control

Question 13

small effector molecules

Answer 13

binds to repressor and causes conformational change

impacts whether or not regulatory transcription factor can bind to DNA

sometimes acts as inducer core press or

Question 14

prokaryotic gene regulation parts

Answer 14

operon ( containing two or more structural genes, promoter, and operator) and regulatory genes

Question 15

operon

Answer 15

made up of two or more structural genes, promoter, and operator

Question 16

structural genes

Answer 16

get transcribed and get turned into proteins

their gene products lead to cellular structures/proteins

Question 17

promoter

Answer 17

controls where/when transcription occurs

Question 18

operator

Answer 18

regulatory dna sequence like an on/off switch

Question 19

regulatory genes

Answer 19

regulate gene expression

encodes gene products that regulate gene expression

Question 20

organization of lac operon

Answer 20

contains a lac promoter(lacP), lac operator(lacO), and lac genes(lacZ,lacY, lacA)

Question 21

what do lac genes in lac operon do

Answer 21

they encode for proteins that break down lactose when transcribed

Question 22

lac regulatory gene

Answer 22

lacl
encodes lac repressor

has its own promoter (i promoter)

Question 23

example of negative control

Answer 23

lac operon with a repressor protein

Question 24

how does the presence/ absence of lactose affect the lac operon

Answer 24

when lactose is absent, the lac repressor binds to the operator and transcription is blocked

when lactose is present, the lac repressor is released from the operator and transcription proceeds at a slow rate

Question 25

why does transcription occur when lactose is present

Answer 25

in its presence, allolactose(small effector molecule) is made and binds to the lac repressor, preventing it from binding to the operator and transcription proceeds

Question 26

inducible operon

Answer 26

usually off but can be stimulated (induced) to turn on when a specific small molecule interacts with the repressor protein

lac operon with a repressor protein q

Question 27

example of positive control

Answer 27

lac operon with an activator protein
E.Coli

Question 28

what does e.coli use to determine its activity

Answer 28

glucose and lactose

when glucose and lactose are both present in the environment, bacteria prefers glucose

when lactose is present, and glucose conc. is low, then bacteria uses lactose

Question 29

Catabolite activator protein CAP

Answer 29

an activator of lac operon

also known as cAMP receptor protein
CRP

Question 30

cAMP

Answer 30

small effector molecule
controls CAP
accumulates when glucose is low

Question 31

how does cAMP regulate transcription

Answer 31

when cAMP binds to CAP, complex binds to CAP site near the lac promoter, which increases RNA polymerase binding and transcription occurs

Question 32

glucose conc. levels effects on cAMP

Answer 32

when glucose is low, cAMP increases
when glucose is high, cAMP decreases

Question 33

when lactose is present and glucose is low

Answer 33

the lac operon is turned on

abundant lac mRNA is synthesized

cAMP levels will be high and CRP is active

CRP binds to CRP-binding site, and the cAMP-CRP complex stimulates the RNA polymerase binding to the promoter, increasing transcription

Question 34

when lactose and glucose are present, the lac operon

Answer 34

is turned on but is working less

cAMP levels will be low, then CRP is inactive

less CRP binds to the site so RNA polymerase less likely to bind to the promoter, leading to lower transcription rates

Question 35

example of negative control: trp operon with a repressor protein

what does trp operon do

Answer 35

trp—> tryptophan amino acid
repressive operon
builds things up unlike lac operon
biosynthesizes

Question 36

in the absence of tryptophan what occurs to trp operon

Answer 36

the trp repressor dissociates from the operator and RNA synthesis proceeds

Question 37

when tryptophan is present..

Answer 37

the trp repressor binds the operator and RNA synthesis is blocked

Question 38

repressible operon

Answer 38

usually on, but can be inhibited(repressed) when specific small molecules interact with the repressor

Question 39

trp how it works

Answer 39

O= operator
P = promoter
trpR = trp regulatory gene

when tryptophan is low, trp repressor is inactive and can’t bind to operator site, trp operon transcription occurs

when tryptophan is present, trp repressor is activated and binds to operator site, and trp operon stops which inhibits transcription