Topic B

Question 1

mutation

Answer 1

A mutation is a heritable alteration/change in the nucleotide
sequence of cellular DNA.

The effect of a mutation can depend on where it occurs in the genome

Question 2

mutant

Answer 2

A mutant is an organism/cell bearing a mutation that expresses itself in the phenotype of the organism/cell

Question 3

Genetic variation is the result of:

Answer 3

Mutation

Recombination (new combinations of genetic material through crossing over in meiosis)

Mutation is the ultimate source of evolutionary change and mutants are one of the best tools available to geneticists

Question 4

Somatic mutations

Answer 4

In the soma(body) of organism.

results in a patch of affected are however, none of the gametes carry the mutation

Question 5

Germline Mutations

Answer 5

Occurs in gametes

All cells in gamete have the mutation therefore the mutation will be passed on to next generations.

Mut is found throughout body and half the gametes carry the mutation

Question 6

Spontaneous mutations

Answer 6

Mutations may arise Spontaneously (without outside forces)

Result from normal cellular / biological processes

Question 7

Induced mutations

Answer 7

Mutations may be Induced by agents called Mutagens

Three broad classes of mutagens

Chemical

Physical
-Ionizing radiation
-Non-ionizing radiation (UV light)

Biological
-Transposable elements (GENE 369/370)
-Viruses / Bacteria (infectious agents)

Question 8

point mutations

Answer 8

Mutations may affect
Single base pairs, or a small number of adjacent base
pairs (point mutations)

Question 9

gene

Answer 9

A gene is a unit of heredity that may influence the outcome of an organism’s traits
A gene contains the information to make a functional product – either an RNA or a protein
Genes reside at fixed locations on a chromosome called a locus or loci (plural)

Question 10

The central dogma

Answer 10

DNA—> RNA—> Protein

Replication
- DNA Polymerase
- New DNA

Transcription
- RNA Polymerase
- mRNA

Translation
- Ribosomes/tRNA
- Polypeptide

Question 11

Diploids

Answer 11

Diploids have two copies of each chromosome — homologous chromosomes
- Therefore diploids have two copies of each gene
- Mutation can result in the production of different forms of a single gene – called alleles

Two alleles of each gene
- Heterozygous
- Homozygous

Wildtype alleles
- Most commonly seen alleles

A single gene may have many different alleles

Question 12

Consequences of point mutation at the promoter

Answer 12

Impact on RNAP binding: prevented
Impact on transcript levels: no transcript
Impact on gene product levels: no polypeptide
Impact on total gene product activity: no activity
Term to describe mutation: knockout/null

Impact on RNAP binding: decreases
Impact on transcript levels: decreases
Impact on gene product levels: less
Impact on total gene product activity: less
Term to describe mutation: knockdown

Impact on RNAP binding: increases
Impact on transcript levels: increases
Impact on gene product levels: more
Impact on total gene product activity: more
Term to describe mutation: overexpression

Impact on RNAP binding: no diff in expression
Impact on transcript levels: no change
Impact on gene product levels: no change
Impact on total gene product activity: no change
Term to describe mutation: silent

Question 13

Consequences of point mutation at the coding region

Answer 13

Impact on polypeptide function/activity: no impact in function
Term to describe mutation: silent

Impact on polypeptide function/activity: abolished
Term to describe mutation: loss of function/knockout/null

Impact on polypeptide function/activity: reduced
Term to describe mutation: knockdown

Impact on polypeptide function/activity: increased or new
Term to describe mutation: gain of function

Question 14

Amino acid properties

Answer 14

nonpolar
polar,uncharged
polar,negativelycharged
(acidic)
polar,positivelycharged (basic)

Question 15

Nonsense mutation

Answer 15

Causes replication to stop

Huge impact on polypeptide

Would probably be worse than missense b/c of potentially stopping too early.

Question 16

Missense conservative

Answer 16

New amino acid —> missense
But chemical properties are the same —> conservative

Ex: basic —> basic
Same biochemical family but could still change function, just won’t know until do experiment

Question 17

Missense non-conservative

Answer 17

New amino acid —> missense

Diff chemical properties —> non-conservative

This more likely to be detrimental to function of polypeptide

Question 18

Deleterious mutations

Answer 18

• decrease the fitness of individuals (impede the organism’s ability to transmit its genes).
• change the end-product of a gene to a less efficient or non-functional form.
• the effect can range from being only slightly negative to being lethal.

Question 19

Beneficial mutations

Answer 19

• increase the fitness of individuals (improve the organism’s ability to transmit its genes).
• change the end-product of a gene to a more efficient form or create a new function altogether.
• beneficial mutations are those that make individuals stronger, or more resistant to a particular disease, or more tolerant to a particular environmental stress.

Question 20

Neutral mutations

Answer 20

• have no effect on the fitness of individuals (do not alter the organism’s ability to transmit its genes).
• includes: mutations in non-coding regions of DNA, mutations that occur in a gene but do not affect the product of that gene, mutations that result in a new phenotype that has neither a positive nor negative effect on an individual in their current environment.

Question 21

Defective Repair

Answer 21

1. Recognition of damage
2. Damage is marked
3. DNA is cleaved around the damaged area
4. Damaged region is excised
5. Repair is carried out through DNA synthesis
6. New and preexisting DNA are joined

Question 22

INDELS

Answer 22

Insertion or deletion mutations