Mutations and genetic diversity

Question 1

Mutation definition

Answer 1

Change in a DNA base sequence

Question 2

How do gene mutations result in a non-functioning protein?

Answer 2

Change in the DNA base sequence changes amino acid sequence which changes tertiary structure and function of protein

Question 3

Why could a mutation potentially not change the function of a protein?

Answer 3

DNA is degenerate

Question 4

Substitution mutation definition

Answer 4

One base is substituted for another base

Question 5

Frame shift mutation definition

Answer 5

One base is added or deleted, meaning all the triplets/codons following the mutation will change

Question 6

Mutagenic agent definition

Answer 6

Increase the chance of mutations

Question 7

What are 4 examples of mutagenic agents?

Answer 7

1. Ionising radiation
2. UV radiation
3. Some viruses
4. Some chemicals

Question 8

What is chromosome non-disjunction?

Answer 8

Homologous chromosomes/sister chromatids aren’t separated during meiosis

Question 9

What is the result of chromosome non-disjunction?

Answer 9

One gamete will have an extra chromosome, one gamete will have one less chromosome

Question 10

Genetic diversity definition

Answer 10

The number of different alleles of genes in a population

Question 11

How is genetic diversity increased?

Answer 11

1. Random mutation in DNA
2. Different alleles being introduced (gene flow)

Question 12

How is genetic diversity reduced?

Answer 12

Geographical isolation or population reduction

Question 13

How does geographical isolation reduce genetic diversity?

Answer 13

1. A few organisms are geographically isolated
2. Only a small number of DIFFERENT alleles from the original gene pool
3. Gene pool may not be representative of population they came from

Question 14

How does reduced population reduce genetic diversity?

Answer 14

1. Event occurs which causes a huge reduction in a population
2. Reduces number of DIFFERENT alleles in a gene pool
3. Survivors reproduce, creating a larger population from a few individuals

Question 15

What are the consequences of low genetic diversity?

Answer 15

1. Greater incidence of genetic disease
2. If environment changes, population has less ability for natural selection

Question 16

What is the anagram for natural selection?

Answer 16

Mass Rift

Mutations (already present)
Alleles (advantage)
Selective advantage/pressure (environment change = different selective pressure)
Survive
Reproduce
Inherit alleles
Frequency of alleles increases
Time (over many generations)

Question 17

What are the 3 types of adaptation?

Answer 17

Behavioural, physiological and anatomical

Question 18

What is stabilising selection?

Answer 18

*Occurs in populations where the environment is stable

*Selective pressure at both ends of the distribution (e.g. low/high birth mass less likely to survive)

*Favours the average (e.g. middle birth mass)

*Tends to eliminate extremes (too high/low)

*Reduces variability, opportunity for evolutionary change and the range of possible characteristics

Question 19

What is directional selection?

Answer 19

*Mutation already present

*Environmental change produces a new selective pressure (e.g. antibiotics) that favours an extreme characteristic (e.g. high resistance allele)

*Over time selection means these will predominate and the mean will shift

E.g. Antibiotic resistance allele of bacteria

Question 20

What is disruptive selection?

Answer 20

Favours BOTH extremes and could lead to SPECIATION

Question 21

How do bacteria obtain multiple antibiotic resistance?

Answer 21

Random Mass Rift to antibiotic A

THEN

NEW random Mass Rift to antibiotic B (NEW selective pressure)

Question 22

What is vertical gene transfer?

Answer 22

Antibiotic resistance alleles are in PLASMIDS, passed through BINARY FISSION

Question 23

What is horizontal gene transfer?

Answer 23

1. Antibiotic resistance allele normally found on plasmid
2. Plasmid replicates
3. Pilus forms a conjugation tube between the resistant bacterium and another bacterium
4. Copy of the plasmid DNA passes through the tube
5. Both bacterial cells now contain the allele for antibiotic resistance

Question 24

What 3 genetic factors cause genetic diversity/variation?

Answer 24

1. Crossing over
2. Random fertilisation of gametes
3. Independent segregation

Question 25

What 2 environmental factors cause genetic diversity?

Answer 25

1. Mutations
2. Interbreeding

Question 26

Polygene definition

Answer 26

Effect on a phenotype is too small to be observed but can act together with others to produce observable variation

Question 27

What is continuous variation?

Answer 27

Can take any value in a range, results from many different genes (polygenic), environmental factors have a LARGE impact

Question 28

What is discontinuous variation?

Answer 28

Only has discrete categories, results from just genetics, environment has LITTLE/NO influence