inheritance

Question 1

what is a locus?

Answer 1

gene occupying a specific section of a chromosome

Question 2

what is codominance?

Answer 2

when both alleles are homozygous dominant, both are expressed in the phenotype

Question 3

what is sex linkage?

Answer 3

characteristics that are influenced by genes on the sex chromosomes (usually X chromosome as it has more genes)

Question 4

what is an example of a sex-linked disease?

Answer 4

haemophilia

Question 5

what is autosomal linkage?

Answer 5

when both alleles occur on the same autosome so the alleles are inherited together unless crossing over occurs

Question 6

what is incomplete dominance?

Answer 6

neither allele is dominant hence both alleles contribute to the phenotype

Question 7

what is epistasis?

Answer 7

interaction between different genes, where the expression of one gene is affected by the expression of another gene at a different locus

Question 8

what is mendels expected ratio of dihybrid crosses?

Answer 8

9:3:3:1

Question 9

what factors affect evolution?

Answer 9

• sexual selection
• gene flow
• genetic drift
• natural selection

Question 10

what is a genetic bottleneck?

Answer 10

50% or more of a population are killed which reduces the gene pool

Question 11

what is the founder effect?

Answer 11

a new colony has started by a few members of the original population

Question 12

what are two isolating mechanisms?

Answer 12

• geographical isolation
• reproductive isolation

Question 13

what is the selective breeding process?

Answer 13

• select organisms with best characteristics
• breed them and select the best offspring
• continue over several generations

Question 14

what are the pros and cons of selective breeding?

Answer 14

pros: maximise crop yield
cons:
- smaller gene pools
- animal discomfort/ethical problems
- inbreeding

Question 15

why is a large gene pool necessary?

Answer 15

effect of chance variation in gene frequencies are minimised

Question 16

what events are involved of the formation of a new species?

Answer 16

• gene pool
• selection pressures
• change in the environment

Question 17

how can autosomally linked genes be arranged?

Answer 17

• different segments of the same chromatid
• same place on opposite chromatid that might have a different allele

Question 18

what is meant by the term monogenic inheritance?

Answer 18

inheritance of a single gene

Question 19

what is meant by the term gene pool?

Answer 19

the total number of different genes present in an interbreeding population

Question 20

what is meant by the term genetic drift?

Answer 20

a change in the allele frequency of a population due to chance

Question 21

what is stated by the Hardy Weinberg principle?

Answer 21

in a stable population with no disturbing factors, the allele frequencies of a gene will remain the same from one generation to the next

Question 22

list the conditions which must be met for the Hardy Weinberg principle to apply

Answer 22

• there is no mutations, selection or migration
• the population is very large or big and genetically isolated
• mating is random