Lesson 8 Gene Regulation in Bacteria Flashcards Preview

Genetics > Lesson 8 Gene Regulation in Bacteria > Flashcards

Flashcards in Lesson 8 Gene Regulation in Bacteria Deck (44)
Loading flashcards...
1

What is transcriptional regulation?

Gene regulation that occurs during transcription.

2

What kind of gene regulation is most common in bacteria?

Transcriptional regulation

3

What are the two types of regulatory proteins?

Repressors and activators

4

Repressor protein

Regulatory protein that binds to the DNA to inhibit transcription

5

Activator protein

Proteins that increase the rate of transcription

6

Negative control

Transcriptional regulation by repressor proteins

7

Positive control

Transcriptional regulation by activator proteins

8

How does an effector molecule exert its effects?

It binds to a regulatory protein such as an activator or a repressor.

9

Inducer

Small molecule that will cause transcription to increase

10

Corepressor

Small molecule that binds to a repressor protein and causes protein to bind to the DNA

11

Inhibitor

A molecule that binds to an activator protein and prevents it from binding to the DNA

12

operon

Area in which two or more structural genes are under the transcriptional control of a single promoter

13

Is it common for bacteria to have genes in operons?

yes

14

What surrounds an operon?

A promoter to signal beginning of transcription and a terminator to signal the end of transcription.

15

What regulates the promoter of an operon?

An operator site

16

What does the lac operon do?

encodes proteins that are involved in lactose metabolism

17

What is structure of lac operon?

It is made up of two units. The first is known as the lac Oberon and it contains a promoter and three structural genes, lacZ, lacY, lacA. Second unit, with its own promoter, is the lacI gene.

18

What protein regulates the lac Oberon? H
ow?

Lac repressor protein. It binds to the operator site and prevents RNA polymerase from sliding past the operator site and transcribing the lacZ, Y and A genes.

19

What dictates the ability of lac repressor to bind to operator site?

It depends on whether or not allolactose is bound to it. When allolactose binds to the repression, it causes a conformational change that prevents the lac repression from binding to the operator site. Under these conditions, RNA polymerase will transcribe the Oberon.

20

What is induced?

Transcription is startedf

21

What is repressed?

Repression is bound to the operator site, so there is no transcription.

22

Experiment 14A: lacI gene
Hypothesis

If the lacI gene encodes a repressor protein, then the lacI gene itself does not have to be physically next to the lac Oberon to repress it; the protein can diffuse throughout the cell and bind to an operator site regardless of the physical location of the lacI gene.

23

Experiment 14A: lacI gene
How were the data interpreted?

Yellow production in original mutant strain was same with or without lactose. This was expected because beta-galactosidase there was constitutive.
In merozygote, an absence of lactose repressed lac operons. With lactose, both operons (the one on chromosome and the one on the F' factor) were induced, yielding a higher level of beta-galactosidase activity in the merozygote.

24

Trans-effect

Form of genetic regulation that can occur even though two DNA segments are not physically adjacent.

25

cis-effect or CIS-acting element

DNA segment that must be adjacent to the gene(s) it regulates

26

Experiment 14A: lacI gene
What was difference between mutant and merozygote strains?

Mutant strain was lacI-, lacZ+, lacY+, lacA+
Merozygote was lacI+ and above

27

Why does intracellular concentration of cAMP decrease when a bacterium is exposed to glucose?

The presence of glucose inhibits adenylate cyclase, which is necessary for cAMP synthesis. This decreases rate of transcription. This enables bacteria to use two sugars in a more efficient way. First, they will use glucose, then lactose.

28

How many operator sites does lac operon have?

Three. O1, O2, and O3

29

How do the operator sites of the lac operon work?

The lac repressor must bind to two out of three operators to cause maximal repression. O1 to O2, or O1 to O3, but not O2 to O3.

30

What regulates the trp operon?

A repression protein and attenuation.