U4L4 - Mutations and Gene regulation

Question 1

What are proto-oncogenes?

Answer 1

A group of genes that control cell growth in normal cells, but can become cancerous when they are mutated.

Question 2

What are oncogenes?

Answer 2

When proto-oncogenes are mutated, they become oncogenes and cause uncontrolled cell division = malignant tumors,

Question 3

What are Carcinogens?

Answer 3

Agents that cause cancer (mutations). They include radiation, smoking, and viruses (HPV).

Question 4

What is a mutagen?

Answer 4

an environmental agent that directly alters the DNA within a cell

Question 5

What is a Spontaneous mutation?

Answer 5

caused by error in DNA replication
EX:
Alkylation – adding alkyl groups (C-groups) to DNA
Oxidation – oxidized bases in DNA

Question 6

What is a Induced mutation ?

Answer 6

caused by environmental agent
EX:
Radiation: UV, Gamma, Beta, Alpha,
Chemical: CO, smoke, nitrosamines (smoked meat & fish)

Question 7

What is a point mutation?

Answer 7

replacement of a single nucleotide in a gene (substitution, insertion, deletion, inversion of base pair)

Question 8

What is a silent mutation?

Answer 8

no change in a.a

Question 9

What is a missense mutation?

Answer 9

codon change results in a different a.a

Question 10

What is a nonsense mutation?

Answer 10

Codon change results in a premature stop codon

Question 11

What is a Frameshift Mutation?

Answer 11

insertions or deletions of nucleotides that is not divisible by 3. The reading frame “shifts” which gives a completely different a.a sequence

Question 12

What is controlling gene expression?

Answer 12

Not all proteins are needed by all cells at all times. It is Inefficient for a cell to transcribe and translate ALL of its genes at all times. Thus, some genes are turned off and on when needed = gene regulation

Question 13

What are the four ways eukaryotes control gene expression?

Answer 13

1) Transcriptional control
2) post-transcriptional control
3) Translational control
4) post-translational control

Question 14

What is Transcriptional control (as mRNA is synthesized) ?

Answer 14

selection of genes to be transcribed and the rate of transcription
E.g. methyl group added to promoter so RNA polymerase can’t bind and transcribe

Question 15

What is post-transcriptional control (as mRNA is processed)?

Answer 15

processing of mRNA and the rate at which mRNA leaves the nucleus.
E.g. masking proteins bind to mRNA and inhibit further processing or alternative splicing

Question 16

What is translational control (as protein is synthesized)?

Answer 16

how long mRNA remains in the cytoplasm
E.g. variation in length of poly-A tail related to rate of translation

Question 17

What is post-translational control (after protein synthesis)?

Answer 17

additional processing that proteins require to be functional or through feedback inhibition.
E.g. presence of hormones lengthen or shorten time that a protein is functional, or “tagged” proteins are degraded

Question 18

What controls gene expression in prokaryotes?

Answer 18

Gene expression is in response to the concentrations of two molecules:
Lactose (source of energy)
Tryptophan (aa used to make proteins)

Question 19

What is an Operon and what is it composed of?

Answer 19

it is a cluster of genes code for a protein commonly regulated and transcribed into mRNA and it consists of; Structural genes (genes encoding for protein), Promoter (nucleotide sequence allows for binding of RNA polymerase for transcription to begin), Operator (base sequence controls transcription), Regulatory genes (encodes for repressor protein), Repressor and activator proteins (proteins that bind to operator to repress or activate gene
transcription)

Question 20

How does Lactose metabolism in E. coli worl?

Answer 20

1) Transport lactose into the cell
2) Break down lactose into glucose and galactose
—-> The enzyme Beta-galactosidase breaks down lactose into glucose and galactose

Question 21

Explain the role of lactose

Answer 21

Lactose is called an inducer molecule because it signals the production of
1) Beta-galactosidase: the enzyme that cleaves lactose into glucose and galactose
2) Galactoside permease: the transport protein that allows lactose to enter a cell