Lecture 11- Regulation of Gene Expression

Question 1

Housekeeping genes

Answer 1

Genes that are always on, and thus can be used as controls when testing for gene activity in experiments

Question 2

How do organisms respond to changing environmental conditions?

Answer 2

-They do so by altering their gene expression, with one of the mechanisms being to regulate the expression of mRNA from genomic DNA, or in other words, transcription. This is the predominant level of regulation in prokaryotes.

Question 3

LacZ

Answer 3

• The first structural gene in the lac operon after the operator
• Codes for beta-galactosidase enzyme, which breaks lactose into galactose and glucose

Question 4

LacY

Answer 4

• The second structural gene in the lac operon

- Codes for permease, which facilitates the transport of lactose into the cell

Question 5

LacA

Answer 5

-Codes for transacetylase

Question 6

Constitutively OFF Mutants in Lac Operon examples

Answer 6

• Mutations in the genes that code for LacZ and LacY ( and I would assume LacA as well) cause enzymes necessary for the processing of lactose to not be made, which prevents lactose from being made properly, leading to a constitutively off mutant. This problem arises in translation, however.

Question 7

cis-acting element

Answer 7

• a DNA sequence that regulates expression of a gene nearby on the same chromosome
• typically a promoter or operator

Question 8

trans-acting element

Answer 8

• factors (usually proteins) that control expression of a gene through interaction with a cis element
• Ex: transcription factor, repressor

Question 9

transcription factor

Answer 9

• a protein that controls the rate of transcription of genetic information from DNA to messenger RNA by binding to a specific DNA sequence.