Class Discussion exam 3

Question 1

What is the 5’ end of the strand called?

Answer 1

free phosphate group

Question 2

What is the 3’ end of the strand called?

Answer 2

Hydroxyl group (attachment site)

Question 3

Do eukaryotes have operons?

Answer 3

NO. just prokaryotes

Question 4

What is the lac repressor?

Answer 4

The PROTEIN that sits down and blocks RNA polymerase

Question 5

Regulatory elements

Answer 5

DNA

Question 6

What is the promotor?

Answer 6

Region of DNA that proceeds the coding sequence

Question 7

What is the TATA box?

Answer 7

Signal that says “hey there’s a coding sequence coming up”

Question 8

What are the steps of the hierarchy of eukaryotic compaction? (smallest to largest)

Answer 8

1) DNA double helix
2) Nucleosomes (“beads on strings”)
3) 30-nm fiber
4) Radial loop domains
5) Heterochromatin
6) Metaphase chromosome

Question 9

Why is prokaryotic gene regulation important?

Answer 9

Responds to changes in the environment

Question 10

What does lactose permease do?

Answer 10

transports lactose into the cell

Question 11

What does B-galactosidase do?

Answer 11

breaks down lactose (product = allolactose)

Question 12

What happens when lactose levels drop?

Answer 12

Proteins are no longer made

Question 13

_____ genes are unregulated and have essentially constant levels of expression.

Answer 13

Constructive

Question 14

All the cells contain the same genome but express different ______ due to ________.

Answer 14

Proteomes, gene regulation

Question 15

What are repressors?

Answer 15

Inhibit (restrain) transcription
(SHUTS IT DOWN)
- negative control

Question 16

What do activators do?

Answer 16

Increase the rate of transcription

- positive control

Question 17

What is an allosteric site?

Answer 17

If there’s a ligand binding, it’s going to initiate a conf. change or a shift in 3D structure

Question 18

What is a small effector molecule?

Answer 18

changes the shape and changes whether or not it can bind to DNA

Question 19

What is an operon?

Answer 19

a CLUSTER of genes under transcriptional control of one promotor
- ONLY in bacteria

Question 20

When the operon controls genes that function in CATABOLISM:

• Regulation is usually _____
• Gene product acts as an ________

Answer 20

inducible, inducer (TURN ON)

Question 21

When the operon controls genes that function in anabolism:

• Regulation is usually by _____
• Gene product acts as a ______

Answer 21

repression, inhibitor (TURN OFF)

Question 22

What does the lac operon do?

Answer 22

in E. coli genes for lactose metabolism

Question 23

What does the lacP (lac promotor) do?

Answer 23

lac promotor

• regulatory DNA sequence that resides in the beginning of genes
• “flashing red light” for RNA synthesis

Question 24

What does the lacZ (beta-galactosidase) do?

Answer 24

Breaks down galactose and produce allolactose

Question 25

What does the lacY (lactose permease) do?

Answer 25

transmembrane protein that allows lactose to enter cell

- encodes lactose permease

Question 26

What does the lacA (galactosidase transacetylase) do?

Answer 26

encodes galactoside transacetylase