Lecture 6

Question 1

Why do TFs bind to several adjacent bp?

Answer 1

To increase specificity and strength

Question 2

Why do TFs bind to dsDNA?

Answer 2

opening the DNA would take too much time and energy

Question 3

What type of sugar is lactose?

Answer 3

disaccharide

Question 4

What does beta-galactosidase do?

Answer 4

breaks lactose to monosaccharides

Question 5

What does lactose break down into?

Answer 5

Glucose and galactose

Question 6

What is a gene?

Answer 6

DNA region responsible for the production of an RNA molecule (mRNA, rRNA, etc)

Question 7

A gene has a promoter, a transcribed region, and a terminator region. In detail, what does the promoter and terminator do?

Answer 7

promoter: upstream (5’ side) of the coding region of a gene

binding site for RNA polymerase and TFs

determines where transcription begins and which DNA strand is used as the template

transcription starts at +1 site immediately downstream

*TATA box for eukaryotes

-35 region and -10 region (pribnow box) recognized by sigma factor of RNA polymerase in prokaryotes

terminator region: downstream (3’ side) of the coding region

signals RNA polymerase to stop transcription and release RNA transcript

rho-independent and dependent terminator in prokaryotes

termination occurs after a poly-A-tail in mRNA in eukaryotes

Question 8

What does upstream mean?

Answer 8

toward the 5’ end

Question 9

A gene has a promoter, a transcribed region, and a terminator region. As a summary, what does the promoter and terminator do?

Answer 9

promoter: place where RNA Pol attaches

terminator: place where RNA Pol leaves

Question 10

In a gene, what does the transcribed region between the promoter and terminator do?

Answer 10

Make RNA

Question 11

Upstream of the promoter (where RNA pol) binds, there is a regulatory region. What does this region do?

Answer 11

TFs bind here

Positive TFs recruit RNA Pols

Negative TFs block the promoter

Question 12

What type of TF is MyoD

Answer 12

positive

Question 13

How do TFs bind to DNA?

Answer 13

with hydrogen bonds between amino acids and bases

Question 14

What does the E. coli lac operon do? Lacl?

Answer 14

lacZ: encodes B-galactosidase (break down lactose -> glucose + galactose)

lacY: encodes lactose permease (imports lactose into the cell)

lacA: encode transacetylase (less important)

all three genes share a single promoter and operator region

operator sites O3 and O1 (respectively) flank the promoter

when lacl binds O1 (and loops to O3), RNA polymerase is blocked -> transcription OFF

Question 15

What does the lacl gene do?

Answer 15

Encodes the lac repressor protein (lacl), which binds to the operator (O1, O2, O3) to block transcription when lactose is absent

when it binds, it bends the DNA into a loop

always present, controlled by lactose (has a decreased affinity for DNA when lactose is present)

It is a negative TF

homotetramer

Question 16

Is everything about the lac operon (lacl, lacZ, lacY, lacA) in eukaryotes or prokaryotes?

Answer 16

prokaryotes

Question 17

What is the purpose of lac operon?

Answer 17

allows e. coli to use lactose only when glucose is absent

Question 18

What is an allele?

Answer 18

different forms of a gene

shown with superscripts or capitalization

Question 19

What is a functional allele for an “A-gene?” non-functional?

Answer 19

A(superscript)+ or A

A(superscript)- or a

Question 20

What is the functional allele of LacZ? Non-functional?

Answer 20

LacZ(superscript)+

LacZ(superscript)-

Question 21

What else can B-Gal break down?

Answer 21

a synthetic molecule called X-gal

when X-gal is acted on by lacZ, it cleaves, and an insoluble blue compound is released