Chapter 18 Reg Gene Exp

Question 1

Operon

Answer 1

Found in bacteria and is a model for us to study. It consists of a gene cluster.

Question 2

Inducible operon

Answer 2

Normally not functioning but can be activated when needed.

Question 3

Repressible operon

Answer 3

Normally functioning but can be shut off.

Question 4

Lac Operon

Answer 4

Inducible system. 3 parts:
A) Operator: binding site available for repressor protein that can prevent transcription. On/off switch
B) Promoter: Site for RNA polymerase
C) Operon genes

Question 5

Coding region and regulatory region

Answer 5

Structural genes are in the coding region. Operator and repressor are in the regulatory region.

Question 6

E.coli and Lac Operon

Answer 6

E.coli can use lactose as an energy source when glucose levels are low. Cyclic AMP also accumulates and binds to catabolic activator protein (CAP). CAP binds to upstream of the promoter and aids in the attachment of RNA polymerase to the promoter.

Question 7

Lac operon dual control

Answer 7

1) Negative control by the lac repressor protein

2) Positive control by CAP

Question 8

Trp Operon

Answer 8

Tryptophan, repressible operon. Trp is the correpressor. Anabolic process.

Question 9

Eukaryotic Gene Expression

Answer 9

2% of DNA codes for proteins.

Question 10

Chromatin structure can be regulated

Answer 10

A) Genes with heterochromatin are highly condensed and not normally expressed
B) Histones are actylated allowing for less tightly packing of chromatin- Histone acetylation promotes transcription.
C) DNA methylation reduces gene expression. Demethylation can activate genes.

Question 11

Non coding RNA molecules are

Answer 11

Involved with gene expression control

Question 12

MicroRNA and siRNA

Answer 12

miRNA and small interefering RNA molecules can bind to mRNA.

1) Degrade mRNA
2) Bind to mRNA and there block translation