Lecture 22: Gene Regulation

Question 1

Housekeeping genes

Answer 1

Genes that every cell must express for basic functions(transcription, metabolism)

Question 1

If all cells share the same alleles and genes why do they all look different?

Answer 1

Specific cells(skin cells, haemoglobin) express different genes

Question 2

Examples of housekeeping genes?

Answer 2

-RNA polymerase
-Mitochondria ATPase
-Actin
-Succinate Dehydrogenase

Question 3

True or False: All steps of the central dogma are subject to regulation?

Answer 3

True

Question 4

What is the main way to determine cell type?

Answer 4

Regulation of transcription, cells won’t express unnecessary mRNAs

Question 5

In both prokaryotes(operons) and eukaryotes what is regulated at transcription?

Answer 5

Promoter

Question 6

Promoter of eukaryotic organisms?

Answer 6

-Made up of a TATA Box

Question 7

Poly I
Poly II
Poly III

Answer 7

Poly I: Transcribes rRNA
Poly II: Transcribes mRNA
Poly III: Transcribes tRNA

Question 8

Transcription Factors

Answer 8

TFII are transcription factors that must prepare the way for RNA polymerase II to transcribe DNA.
Multiple TF bind before finally recruiting the RNA polymerase II. They then give RNA polymerase permission to start transcribing

Question 9

Two reasons why enhancers and silencers are special?

Answer 9

1. They can act at a great distance up to 20000 bp away
2. They can act in either orientation(inverted)

Question 10

What do enhancers and silencers do?

Answer 10

Enhancers: Recruit activator proteins and help RNA polymerase work more efficiently
Silencers: Recruits repressor proteins and decrease RNA polymerase transcription
FAR from the promoter

Question 11

Most important transcription factor ?

Answer 11

2D

Question 12

Porkaryotic vs Eukaryotic regulation ?

Answer 12

Prokaryotic: Help decide whether the RNA polymerase should start transcribing
Eukaryotic: Give the RNA polymerase permission to transcribe

Question 13

How do enhancers work from so far away?

Answer 13

1. DNA folds
2. The enhancers then bind to the transcription factors which are controlling the RNA polymerase
   3.It will change the configuration of the transcription factors to either enhance or repress transcription

Question 14

Do nucleosomes(DNA coiled around histones) prevent binding of transcription factors and transcription in general?

Answer 14

Yes

Question 15

Heterochromatin?

Answer 15

Tightly wound DNA, that is not transcribed
-Dark stripes on karyotype

Question 16

Eurchromatin?

Answer 16

DNA that is transcribed
-Light stripes on karyotype

Question 17

Why can women have more than one X chromosome?

Answer 17

Females inactivate one of the X chromosomes by condensing it into a state that prevents transcription

Question 18

What is it called when an X chromosome is turned off?

Answer 18

The X chromosome becomes a BARR BODY

Question 19

What is the number of Barr Body?

Answer 19

Number of chromosomes minus one(must have one active X chromosome always)

Question 20

Lyonization

Answer 20

Different cells will have different X chromosomes condensed. If the active X chromosomes have different alleles then different parts of a females body could have different phenotypes

Question 21

Gene Amplification

Answer 21

-An increase in the number of copies of genes
- Cancer cells

Question 22

Alternative Splicing

Answer 22

Sometimes while splicing out introns, exons are also spliced out this creates a protein missing a chunk. This can affect the protein function

Question 23

RNA Stability

Answer 23

mRNAs need to constantly be degraded as new ones are constantly being created. A more stable RNA = More resistant to degradation (will stick around longer). Therefore, we want RNAs to be unstable so that RNAs can be degraded

Question 24

mRNA similar to water??

Answer 24

The rate at which water flows out of the water reservoir is determined by the water level
Higher level = faster rate
-The rate of transcription and the rate degradation determines the level of mRNA

Question 25

Translational Control

Answer 25

The concentration of mRNA in a cell determines how much of a protein gets made

Question 26

RNA Interference

Answer 26

-When the cell makes small interfering RNAs that do not encode for a protein but are complementary to the mRNA of a gene
-With the help of a dicer these siRNAs bind to the complementary mRNA and block its transcription

Question 27

Post-translational controls

Answer 27

-The regulation of proteins
-Cyclin and CDK used to regulate the cell cycle by binding together to form kinase
- Kinase helps change the function of a protein from its active form to its inactive form

Question 28

Kinases

Answer 28

Catalyze the transfer of phosphates between substances

Question 29

How are proteins destroyed?

Answer 29

Ubiquitin binds to proteins and then the protein with the ubiquitin binds to a proteasome, the proteasome is a complex that’s job is to destroy proteins back into amino acids that can be reused

Question 30

Is regulating post-transcriptionally better?

Answer 30

Not necessarily.
-Rgulating before transcription is efficient since no energy is used to make mRNAs/proteins, but should a protein be required it will take a while to make the protein
-Regulating proteins post translationally is much faster but involves proteins that spend time doing nothing while waiting to be activated