Lecture 12 - Control of Gene Expression (Ch 8)

Question 1

Proteins that all cell types have are called

Answer 1

housekeeping proteins

Question 2

Of the genes a cell has, how many of the genes would a typical differentiated cell express?

Answer 2

About half

Question 3

Cells from an adult cow or carrot can be de differentiated True or False?

Answer 3

True

Question 4

What can change gene expression? Give an example

Answer 4

External signals like hormones and enzymes can turn a gene off or on- i.e. hormones like cortisol

Question 5

In bacterial transcriptional regulation, what do bacterial promoters bind to and what is it called?

Answer 5

Bacterial promoters bind RNA polymerase using the sigma factor unit

Question 6

In transcriptional regulation, what type of promoters are used for eukaryotes?

Answer 6

Eukaryotic promotors bind general transcription factors, that promote binding of RNA polymerase

Question 7

Regulatory DNA sequences can act on their own, true or false?

Answer 7

False- transcription regulator proteins have to BIND onto DNA sequences

Question 8

How do transcription regulator proteins BIND onto DNA sequences?

Answer 8

noncovalent interactions, in the major groove, and to intact DNA double helix

Question 9

How do transcription regulator proteins increase their contact area, making them stronger and more specific?

Answer 9

They bind as dimers

Question 10

What’s the difference between transcription regulatory sequences and transcription promoter sequences?

Answer 10

One affects levels of RNA produces, and the other affects where transcription starts

Question 11

How are transcription switches typically regulated?

Answer 11

Via food sources (available or not)

Question 12

What happens to the trp
operator when there are high levels of tryptophan?

Answer 12

The trp operon is NOT made (not transcribed, basically) because trp binds to a repressor and activates it, so that means more tryptophan is not made

Question 13

What happens to a trp operon when there are low levels of tryptophan?

Answer 13

The trp operon is MADE (it is transcribed) because the repressor is not activated, so that means it can make more tryptophan

Question 14

The promoter is the middle part of the operator? True or false? What does the promotor do and what does the operator do?

Answer 14

False- the operator is a part of the promoter; operator is a region of DNA that overlaps with or lies just downstream of the RNA polymerase binding site (promoter). That is, it is in between the promoter and the genes of the operon.

Question 15

The repressor is always present in the cell for trp, True or False? What mechanism does the repressor use?

Answer 15

True, but it is not always activated; it uses feedback inhibition

Question 16

What does it mean to use feedback inhibition? Using the trp example

Answer 16

The trp repressor, for example, gets controlled by trp itself

Question 17

What 2 things is the lac operon controlled by?

Answer 17

The lac repressor and the CAP activator

Question 18

What happens when glucose is present near a lac operon and lactose is not? What about when lactose IS?

Answer 18

Even if there is lactose, the lac operon will use the glucose because it likes it more :) buttt if lactose is NOT there and glucose is, then the lac repressor binds to the operator and operator is not transcribed

Question 19

What happens in a non-glucose environment where lactose is present?

Answer 19

If lactose is present and glucose is NOT, then the operon is turned on. CAMP will also bind on CAP site. (ask about this)

Question 20

What happens if a lactose is not there, and glucose is not there either?

Answer 20

If both are not there, cyclic AMP binds to the CAP binding site ANDDD the repressor is free to bind to the mRNA meaning no operon is transcribed

Question 21

CAMP concentrations increase when? what do they do?

Answer 21

when glucose goes down, they metabolise sugars other than glucose

Question 22

What are eukaryotic activators called? How far away do they have to be?

Answer 22

Enhancers; they can work from 1000s of nucleotides away

Question 23

What binds the activator AND the general transcription factors so that they can work together and promote transcription?

Answer 23

Mediator protein complexes

Question 24

Where does the chromatin remodeling complex attach itself to? What does it modify?

Answer 24

It attaches near the TATA box, and what is does is that it covalently changes the histone part of nucleosomes

Question 25

What histone modification helps activate transcription? And what deactivates transcription?

Answer 25

Histone acetyltransferases activate transcription (and deacetylases deactivate transcription aka repress it)

Question 26

How does our body make sure that enhancers are working properly? What do they do?

Answer 26

DNA loops called TADS regulate them; they hold genes and regulatory regions together

Question 27

What does rthe lac operon even do?

Answer 27

It breaks down and digests sugars (it can ONLY digest lactose. bc our body prefers to digest glucose, glucose’s pressence turns lac operon OFF)

Question 28

What dos the trp open even do?

Answer 28

It MAKES trptophan molecules