Chapter 16 pt.1

Question 1

Gene Regulation

Answer 1

The mechanism and systems that control the expression of genes

Question 2

Why do we need gene regulation?

Answer 2

In bacteria, it maintains an internal flexibility, turning genes on and off in response to environmental changes; in multicellular eukaryotic organisms, gene regulation also brings about cell differentiation /specialization

Question 3

Structural Genes

Answer 3

Proteins used in metabolism or biosynthesis which plays a role in the cell (housekeeping genes)

Question 4

Regulatory Genes

Answer 4

Either RNA or proteins interact with other DNA sequences and affect the transcription or translation of those sequences

Question 5

Constitutive Genes

Answer 5

They are genes that are not regulated

Question 6

Positive Control

Answer 6

Mechanisms that stimulate gene expression – regulatory protein is an activator

Question 7

Negative Control

Answer 7

Mechanisms that inhibit gene expression – regulatory protein is a repressor

Question 8

Regulatory genes

Answer 8

Either RNA or proteins interact with other DNA sequences and affect the transcription or translation rate

Question 9

Operon

Answer 9

A group of bacterial structural genes that are transcribed together

Promoter–Operator–geneA–geneB–geneC–

(gene A,B, C ==> structural genes)

Question 10

Operator

Answer 10

affects whether transcription can take place

Question 11

Explain the mechanism of an operon

Answer 11

1. –promoter+regulator– ==> transcription/translation ==> regulatory protein
2. An operon is a group of structural genes plus sequences that control transcription
3. The regulatory protein may bind to the operator site to regulate the transcription of mRNA
4. The products of mRNA catalyze reactions in a biochemical pathways

Question 12

Inducible Operons

Answer 12

Transcription is normally off – sometimes needs to be induced

Question 13

Repressible Operons

Answer 13

Transcription is normally on – something needs to be represented

Question 14

Negative Inducible Operon

Answer 14

• The regulatory protein is a repressor that binds to the operator and prevents transcription of the structural genes
• When an induce is present, it binds to the regulator, thereby making the regulator unable to bind to the operator
• Transcription now takes place

Question 15

Inducer

Answer 15

When bound to repressor protein, inactivate the repressor protein and allow for transcription to occur – the precursor molecule

Question 16

allosteric proteins

Answer 16

which change shape upon binding to another molecule

Question 17

Negative Repressible Operons

Answer 17

1. The regulatory protein is an inactive repressor, unable to bind to the operator
2. Transcription of the structural genes therefore takes place
3. Levels of the product build up
4. Product binds to the regulatory protein
5. Making it activate and able to bind to the operator
6. it prevents transcription

Question 18

Co-repressor

Answer 18

A small molecule that binds to the repressor and makes it capable of binding to the operator – the metabolic product

Question 19

Flip the card! Sums up everything :)

Answer 19

There are two basic types of transcriptional control: negative and positive
- In negative control, where a regulatory protein – acts as repressor – binds to DNA and transcription is inhibited
- In positive control, when a regulatory protein – activator – binds to DNA and transcription is stimulated
- Operons are Inducible: their transcription is normally off and must be turned on through a precursor/inducer
- Operons are repressible: their transcription is normally on and must be turned off through a product/co-repressor

Question 20

Lac operon

Answer 20

negative inducible operon

Question 21

B-galactosidase

Answer 21

• It is encoded by the LacZ gene
• Lactose is broken down into glucose and galactose

Question 22

Permease

Answer 22

• It is encoded by the LacY gene
• It transports lactose into the cell

Question 23

Transacetylase

Answer 23

• It is encoded by the LacA gene
• detoxification/preventing the accumulation of thiogalactoside

Question 24

Coordinate Induction

Answer 24

The simultaneous synthesis of several proteins stimulated by a specific molecule, the inducer

Question 25

Allo-lactose

Answer 25

A compound that plays an important role ins regulating the lac operon in bacteria and is produced by beta-galactoside when metabolizing lactose

***INDUCER –> binds to repressor and allows it to be removed from the operator…which allows transcription to continue to produce enzymes that break lactose into glucose and galactose

Question 26

LacP

Answer 26

Promoter region for the lac operon

Question 27

LacO

Answer 27

Operator for Lac operon – it occupies the 3’ end of the promoter and the 5’end of the LacZ gene therefore inhibits RNA polymerase to bind to the promoter region

Question 28

LacI

Answer 28

Contains the genes for the lac operon repressor – regulatory gene – and has its own promoter

Question 29

If beta-glacatosidase production is repressed, how can lactose metabolism be induced to produce allocates?

Answer 29

Repression never completely shuts down transcription of the lac operon – trace amounts of the enzyme are produced when the repressor is bound

Question 30

IPTG

Answer 30

Another inducer that does not require beta-galactoside (used in research laboratories to examine metabolism-independent process – extra info in brackets)

Question 31

Lactose

Answer 31

A major carbohydrate made up of glucose and galactose

Ex. Found commonly in milk products

Question 32

Partial-diploid

Answer 32

Strains of E.coli that possessed a full bacterial chromosome and an extra piece of DNA

Question 33

Cis Acting

Answer 33

Able to control the expression of genes on the same piece of DNA

Question 34

Trans Acting

Answer 34

Able to control the expression of genes on other DNA molecules

Question 35

What experimental evidence did lacZ and LacY partial diploid genes produce?

Answer 35

A single functional beta-galactosidase gene or a single permease gene was sufficient enough for a functional phenotype whether the function gene was coupled to other functional or other defective gene made no difference

Ex. LacZ+, LacY- / LacZ-, LacY+

MAKES NO DIFFERENCE

Question 36

LacI+

Answer 36

The gene is trans dominant: the repressor produced by lacI+ can bind to both operators – bacterial and plasmid DNA – and repress transcription in the absence of lactose

When lactose is present, it inactive the repressor, and functional Beta-galactosidase is produced from the lacZ+ gene

Question 37

LacI-s

Answer 37

The gene produces a superreppresor that does not bind lactose

The gene is trans dominant: the superrepressor binds both operators and prevents transcription in the presence and absence of lactose – NOT GOOD

Question 38

LacO-c

Answer 38

mutation in the operator inhibits the repressor protein to bind the operator when there is/there is not any lactose

***CIS-ACTING – can be inducible ONLY if when there is no lactose it produces a non-functional beta-galactosidase

Question 39

constitutive

Answer 39

Producing genes regardless of lactose or not

Question 40

LacP+

Answer 40

interfere with the binding of beta galactosidase
***CIS ACTING –an be inducible ONLY if when there is no lactose it produces a non-functional beta-galactosidase