Gene Expression

Question 1

What must prokaryotes and eukaryotes must be able to do?

Answer 1

Regulate which genes are expressed at any given time

Question 2

Genes being turned “on/off” refers to

Answer 2

whether or not transcription will take place which allows for cell specialization

Question 3

Operons

Answer 3

A group of genes that can be turned on or off

Question 4

Three parts of operons

Answer 4

1. Promoter- where RNA polymerase can attach
2. Operator- on/off switch
3. Genes- Code for related enzymes in pathways

Question 5

Repressible operons (on to off)

Answer 5

Transcription is usually on, but can be repressed (stopped)

Question 6

Inducible (off to on)

Answer 6

Transcription is usually off, but can be induced (started)

Question 7

Regulatory gene

Answer 7

Produces a repressor protein that binds to the operator to block RNA
-Always expressed, but at low levels
-Binding of a repressor to an operator is reversible

Question 8

Allosteric Activator

Answer 8

Substrate binds to allosteric site and stabilizes the shape of the enzyme so that the active site remains open

Question 9

Allosteric inhibitor

Answer 9

Substrate binds to allosteric site and stabilizes the enzyme shape so that the active sites are closed.

Question 10

What does the trp operon in bacteria control? (repressible operon)

Answer 10

The synthesis of tryptophan
-Since it’s repressible, transcription is active ‘
-can be switched on/off by trp repressor
-Allosteric enzyme thats only active when tryptophan binds to it

Question 11

What happens when too much tryptophan builds up in bacteria?

Answer 11

Tryptophan is more likely to bind to the repressor turning it active, which will then temporarily shut-off transcription for tryptophan

Question 12

What does the lac operon control? (Inducible operon)

Answer 12

The synthesis of lactase, an enzyme that digests lactose (milk sugar)
-Since inducible, transcription is off
-Inducer for lac repressor is allolactose
*When present it will bind to the lac repressor and tun the lac repressor off
*Genes can now be transcribed

Question 13

Epigenetic inheritance

Answer 13

Chromatin modifications do not alter the nucleotide sequence of the DNA, but they can be heritable for future generations
-Modifications can be reversed unlike mutations

Question 14

Transcription initiation regarding gene expression

Answer 14

Once chromatin modifications allow the DNA to be more accessible, specific transcription factors bind to control elements

Question 15

Control elements

Answer 15

-Sections of non-coding DNA that serve as binding sites
-Gene expression can be increased or decreased by binding of activators or repressors to control elements

Question 16

RNA processing

Answer 16

Alternative splicing of pre-mRNA

Question 17

Translation initiation

Answer 17

-Translation can be activated or repressed by initiation factors
-MicroRNA’s and small interfering RNA’s can bind to mRNA and degrade it or block translation

Question 18

Eukaryotic Development

Answer 18

During embryonic development cell division occurs and cell differentiation occurs
-Cells become specialized in their structure and function

Question 19

Morphogenesis

Answer 19

physical process that gives an organism its shape

Question 20

How do cells differentiate during early development?

Answer 20

1. Cytoplasmic determinants
2. Induction

Question 21

Cytoplasmic determinants

Answer 21

Substances in the maternal egg that influence cells

Question 22

Induction

Answer 22

Cell to cell signals that can cause a change in gene expression

Question 23

What do cytoplasmic determinants and induction influence?

Answer 23

Pattern formation, a “body plan” for the organism

Question 24

Homeotic Genes

Answer 24

Map out the body structures

Question 25

What does apoptosis allow?

Answer 25

Cell death, allows structures to take their form