Population genetics in breeding

Question 1

What are the benefits of using genetics for animal improvement

Answer 1

Assist in meeting market requirements
Improve overall productivity and profitability
Improve specific traits of an animal including:
- growth rate
- carcase yield
- fleece weight
- fibre diameter
- variation in birth weights
- disease resistance

Question 2

what are the sources of genetic variation

Answer 2

Mutations
Gene flow - movement of genes from one population to another
Sex - introduction of new gene combinations

Question 3

What are germ-line mutations

Answer 3

Mutation that occurs in the gametes
These mutations will be passed on to the next generations

Question 4

Describe gene flow within and across populations

Answer 4

Within a population:
- can introduce or reintroduce alleles to a population
- increases genetic variation of population
Across populations:
- genes move around
- can make distant populations genetically similar to one another
- reducing the chance of speciation

Question 5

What is genotype frequency?

Answer 5

the proportion of animals with each genotype

Question 6

A herd of 100 cows: 30 red (RR), 50 roan (RW), 20 white (WW)
Calculate the frequency of R and W allele

Answer 6

Question 7

What is the hardy-weinberg law?

Answer 7

Question 8

If the gene frequency of p=0.6 and q=0.4
Use the hardy-weinberg law to calculate genotype frequencies in the offspring

Answer 8

Question 9

Describe qualitative traits

Answer 9

Qualitative traits - characterised by segregation in classical mendelian ration, purely genetic
e.g., coat colour

Question 10

Describe quantitative/continuous traits

Answer 10

can be given a numerical value on a scale
often polygenic and depend on environmental mechanisms
usually multiply gene loci
e.g., growth rate or milk yield

Question 11

When can a quantitative trait arise from a single genetic loci?

Answer 11

• single polymorphic locus with multiple, differentially expressed alleles
• expression of a quantitative trait controlled by a mutant allele at a single locus with a high degree of variable expressivity

Question 12

what are epigenetics?

Answer 12

heritable changes in gene expression that not caused by changes in DNA sequence
Environmental factors cause genes to behave or be expressed differently