Gene Expression

Question 1

operon

Answer 1

a group of genes that share a single promoter the genes often code for proteins that have related functions

Question 2

monocistronic

Answer 2

each promoter controls one gene - eukaryotic genes specify a signle protein, but splicing allows for variation

Question 3

polycistronic

Answer 3

one promoter controls more than one gene as prokaryotic genes with related function are situated in tandem on the DNA so

Question 4

what are the 2 types of gene regulation?

Answer 4

positive and negative

Question 5

what is a regulatory sequence

Answer 5

a segment on DNA where regulatory protein binds and is capable of increasing or decreasing the expression of a gene

Question 6

what are the types of regulatory sequences and describe them

Answer 6

enhancer - activator binds to increase transcription

operator - repressor binds to deacrease transcription

Question 7

describe positive gene regulation

Answer 7

active form of the regulatory protein turns on or increases the transcription of the operon

turns ON transcription

Question 8

describe negative gene regulation

Answer 8

operons are switched off by the active form of the regulatory protein (repressor)

turns OFF transcription

Question 9

describe a repressible gene

Answer 9

gene expression is normally ON but it can be turned off by an operon

a corepressor will activate a repressor to turn off transcription

Question 10

describe an inducible operon

Answer 10

gene expression is normally OFF but an be turned ON by an operon

an inducer will inactivate a repressor to turn on transcription

Question 11

describe constitutive gene expression

Answer 11

it is unregulated so genes are ALWAYS ON it effect housekeeping genes, regulatory genes

Question 12

describe the anabolic pathway and its relationship to repressible genes

Answer 12

anabolism is the synthesis of molecules from simpler subunits, it is repressed when the thing synthesizes is no longer needed

Question 13

describe the catabolic pathway and its relationship to inducible gene

Answer 13

catabolism is the breakdown of complex molecules into simpler units there is no need to catabolize molecules that are not resent in the cellular environment which leads to a waste of energy SOOOOO only turns on when the nutrient that needs to be broken down is present

Question 14

What is a regulatory gene? Describe it.

Answer 14

a region on DNA that codes for the productioon of the regulatory protein

it is upstream from the operon and has constitutive expression meaning it is continuously transcribed

it allosteric

Question 15

what are the two types of regulatory proteins and describe what they do

Answer 15

repressor - its active form binds to DNA and blocks RNAP fundtion by binding to operator

activator - its active form finds to DNA and enhances RNAPS function by binding to the enhancer

Question 16

what are the components of an operon and describe them

Answer 16

• promoter: region on DNA where RNAP binds to start transcription like an on-off switch for genes
• structural genes: genes to be transcribe by RNAP that have related functions
• regulatory sequence

Question 17

what are the components of operon regulation?

Answer 17

• regulatory gene
• regulatory protein
• effector
• operon (promoter, regulatory sequence)
• structural genes

Question 18

describe the repressible operon trp and the role regulatory genes have in it

Answer 18

it has a repressor coded by a regulatory gene trpR which it itself has a constitutive expression that constantly makes trp repressor and is allosteric

Question 19

effector

Answer 19

any molecule that can regulate the activity of a protein

Question 20

what is a corepressor

Answer 20

activates the repressor causes regulatory protein to bind to the oprator and inactivates gene expression

Question 21

what is an inducer

Answer 21

iactivates the repressor and presents regulatory protein from binding to the operator and activates gene expression

Question 22

what is the effector molecule for trp

Answer 22

corepressor

Question 23

what is the enzyme for lac Z and what is its function

Answer 23

beta galactosidase

lactose hydrolysis into glucose and galactose

Question 24

what is the enzyme for lac Y and what is its function

Answer 24

permease - it is a membrane protein that transports lactive into the cell

Question 25

what is the enzyme for LacA and what is its function

Answer 25

adds acetyl group to galactose