Evolutionary Biology 2

Question 1

Types of selection

Answer 1

• Directional selection - shifts towards one extreme
• Divergent selection - favours variants of opposite extremes
• Stabilising selection - Shifts population towards middle (heterozygotes)

Question 2

How is Genetic variation maintained

Answer 2

• Diplody
• Gene flow (migration)
• Mutation
• Balancing selection

Question 3

Gene flow

Answer 3

transfer of genetic material from on population to another

Question 4

Diploidy

Polyploidy

Answer 4

• 2 sets of chromosomes

- more than 2 sets of chromosomes

Question 5

Types of mutation

Answer 5

Somatic (often has no effect)

Germline - can affect the whole organism

Question 6

Types of germline mutation

Answer 6

• Block mutation - changes to segments of a chromosome, leading to large scale changes to the DNA of an organism, often caused by transposons.
• Point mutation - A mutation affecting only one or a few nucleotides in a gene sequence

Question 7

Types of point mutation

Answer 7

• Subsitution (ATG > ACG) one base is changed
• Insertion (ATG > ATGC) one base is added
• deletion (ATG > AG) one base is removed
• inversion (ATG > AGT) the order is reversed

Question 8

Synonymous/silent substitution

Answer 8

a change in the DNA sequence that codes for amino acids in a protein sequence, but does not change the encoded amino acid.

• occurs due to redundancy of the genetic code (multiple codons coding for one amino acid)

Question 9

non-synonymous substitution

Answer 9

a nucleotide mutation that alters the amino acid sequence of a protein.

Question 10

types of non-synonymous substitution

Answer 10

• Missense
• Nonsense
• Frame shift

Question 11

Missense mutation

Answer 11

point mutation in which a single nucleotide change results in a codon that codes for a different amino acid

Question 12

Nonsense mutation

Answer 12

A nonsense mutation results in a shorter, unfinished protein product. It changes a codon coding for an amino acid into a stop codon.

Question 13

Frame shift mutation

Answer 13

Causes a change in how the DNA sequence is read. Is caused by an insertion or deletion of base pairs (of a number other than 3)

Question 14

2 mechanisms of balancing selection

Answer 14

Heterozygote advantage

Frequency - dependant selection

Question 15

Frequency- dependant selection (FDS)

Answer 15

when the fitness of a genotype depends on its frequency in a population.

Can be both positive and negative

Question 16

Positive FDS

Answer 16

Mullerian mimicry - when two toxic organisms develop similar physical appearance to deter predators

cytotype exclusion

Question 17

Negative FDS

Answer 17

Batesian mimicry - when a harmless organism imitates a toxic one to deter predators

Host-parasite cycles

Question 18

Heterosis

Answer 18

improved function in a hybrid offspring

Question 19

Selection coefficient

Answer 19

measure of differences in relative fitness

Question 20

genetic load

Answer 20

presence of unfavourable genetic material in a population

Question 21

Associative over-dominance

Answer 21

when heterozygote individuals have a higher fitness then homozygote counterparts.