Genetic diversity

Question 1

What is a mutation?

Answer 1

An alteration to the base sequence of DNA
Can arise spontaneously during DNA replication

Question 2

Why might a mutation not change the amino acid sequence?

Answer 2

Genetic code is degenerate
Mutation may occur in the intron

Question 3

Define a substitution mutation

Answer 3

When a nucleotide is replaced by another in the DNA base sequence
No change occurs in the amino acid sequence

Question 4

Define a deletion mutation

Answer 4

When a DNA nucleotide is lost
Causes a frame shift which alters the amino acid sequence

Question 5

What is a mutagenic agent?

Answer 5

A factor that increases the rate of a gene mutation

Question 6

When chromosomes fail to separate during meiosis, what is this known as?

Answer 6

Chromosome non-disjunction

Question 7

How does meiosis differ from mitosis?

Answer 7

Meiosis = produces 4 different cells with half the chromosomes as the parent cells
Mitosis = produces 2 identical cells with the same number of chromosomes as the parent cells

Question 8

Outline the process of meiosis I?

Answer 8

1. Homologous chromosomes pair to form bivalents
2. Crossing over occurs at the chiasmata
3. Homologous chromosomes separate into 2 cells

Question 9

Outline the process of meiosis II?

Answer 9

1. Independent segregation of sister chromatids
2. Each cells divides again to produce 4 haploid cells

Question 10

How does meiosis produce genetic variation?

Answer 10

Crossing over
Independent segregation of homologous chromosomes + sister chromatids

Question 11

Define genetic diversity

Answer 11

Total number of different alleles in a population

Question 12

Why is it advantageous to have a higher genetic diversity?

Answer 12

Improves the ability to adapt to a change in the environment
Allows natural selection

Question 13

How does natural selection bring about new characteristics?

Answer 13

1. Random mutations result in new alleles
2. Certain alleles are better suited for survival and reproduction
3. These offspring receive the new allele
   (4. Frequency increases over many generations)

Question 14

What is directional selection?

Answer 14

Occurs when environment changes
Individuals with phenotypes suited to the new conditions will survive / pass on genes
Over time, the mean population moves towards these characteristics
e.g. antibiotic resistance

Question 15

What is stabilising selection?

Answer 15

Occurs when the environment stays the same
Individuals closest to mean are favoured
New characteristics are selected against
Low diversity
e.g. birth weight

Question 16

Name 3 types of adaptation

Answer 16

1. Anatomical (body structure)
   e.g. oily fur
2. Behavioural (actions)
   e.g. hibernation
3. Physiological (bodily processes)
   e.g. venom production