Variation & Mutations

Question 1

What is a “species”?

Answer 1

A group of individuals that are able to breed and produce fertile offspring.

Question 2

What is a “population”?

Answer 2

A group of organisms of a particular species living in the same place at the same time.

Question 3

What is an allele?

Answer 3

Alternative form of a gene.

Question 4

What is the gene pool?

Answer 4

Sum of all alleles in a given population.

Question 5

What is allele frequency?

Answer 5

How often a particular allele for a gene appears in a given population.

Question 6

What is a genotype?

Answer 6

The genetic constitution of an individual organism

Question 7

What is a phenotype?

Answer 7

The observable characteristics of an organism resulting from the interaction of the genotype with the environment.

Question 8

What is a mutation?

Answer 8

A spontaneous change in a gene or chromosome leading to new characteristics in an organism.

Question 9

What is a gene mutation?

Answer 9

A change in a single gene.

Question 10

What is a chromosomal mutation?

Answer 10

All or part of a chromosome is affected.

Question 11

What is an induced mutation?

Answer 11

A mutation caused by a mutagenic agent.

Question 12

What is a mutagenic agent? Give 3 examples.

Answer 12

An environmental agent that increases the rate of mutation.

Formaldehyde, ionising radiation, mustard gas.

Question 13

What are spontaneous mutations?

Answer 13

Mutations caused by an error in natural biological processes (e.g. non-disjunction in anaphase)

Question 14

What are somatic mutations?

Answer 14

Mutations occurring in body cells.

Individual is affected, offspring will not be affected.

Question 15

What are the 2 classifications of mutations by amount of gene affected?

Answer 15

Gene mutations

Chromosomal mutations

Question 16

What are the 2 classifications of mutations by cause?

Answer 16

Spontaneous mutation

Induced mutation

Question 17

What are the 2 classifications of mutations by cell type affected?

Answer 17

Somatic and germ-line

Question 18

What are germ-line mutations?

Answer 18

Mutations occurring in gametes/sex cells.
Individual can be unaffected.
Mutation will be passed on to offspring.

Question 19

What are the 4 classifications of mutations by effect?

Answer 19

Missense
Nonsense
Neutral
Silent

Question 20

What are missense mutations?

Answer 20

Mutations which cause a change in the amino acid, and therefore the protein produced.

Question 21

What are nonsense mutations?

Answer 21

Mutations which change the base code to “STOP”.

Synthesis of the protein stops, the shorter protein produced may unable to carry out its function.

Question 22

What are neutral mutations?

Answer 22

Mutations which cause a change in an amino acid.

Codon is changed, but is still coded for the same amino acid.

Question 23

What are silent mutations?

Answer 23

Mutations which cause no change in the amino acid.

Question 24

What are the 3 types of point mutations? Provide a brief explanation.

Answer 24

Insertion - new nucleotide is added

Substitution - existing nucleotide is replaced by one with a different base

Deletion - nucleotide is removed

Question 25

What is a frameshift?

Answer 25

A process which occurs when bases have been added or removed, resulting in the codon starting at a different base.

Question 26

What are 5 sources of variation?

Answer 26

1) Crossing over
2) Independent assortment
3) Non-disjunction
4) Random fertilisation
5) Mutations

Question 27

What is trisomy 13? What are the symptoms?

Answer 27

Patau syndrome.

Intellectual disability, microcephaly (small head), extra fingers, cleft palate.
More than 80% die within first month of life.

Question 28

What is monosomy X? What are the symptoms?

Answer 28

Turner syndome.

Short stature, infertility, lack of sexual characteristics

Question 29

What are the 5 main ways that the frequency of alleles in the gene pool change?

Answer 29

1) Genetic drift/founder effect
2) Mutations
3) Natural selection
4) Migration
5) Barriers to gene flow

Question 30

What is random genetic drift?

Answer 30

When the frequency of an allele within a population changes due to chance rather than natural selection.

More prevalent in small populations, as a higher proportion of the population will express the change.