Week 6 - The nature of genetic variation

Question 1

What are traits

Answer 1

Any observable or measurable characteristics of an individual, Eg Observable trait - coat colour, measurable trait - lactation yield, littler size

Question 2

What is phenotype

Answer 2

Appearance or observed performance for a trait in an animal

Question 3

How do you measure value of an animal as a genetic parent

Answer 3

Breeding value

Question 4

What is heritability

Answer 4

a measure of the strength of the realtionship between breeding values and phenotypic values for a trait in a population

Question 5

What are the components the make up phenotype

Answer 5

P = G + E + GE
G = A + D + I
E + TE + PE
A = additive genetic effects
D= dominance effects
I = epistatic effects
TE = temporary environmental effects
PE = permanent environmental effects

Question 6

What is selection

Answer 6

-The process of choosing the parents of the next generation

• The animals that perform better (gain faster, produce more milk, lay more eggs, etc.)
• Have good genes for those traits, desirable to pass on to the progeny

-The poor performing animals have undesirable genes
-Not desirable to pass on to the
offspring

-Goal of selection - to increase the frequency of the good genes in the population

Question 7

what is ASBV

Answer 7

The assessment for how valuable the animal is

Question 8

How are animal populationsimproved genetically?

Answer 8

Selection- choosing animals with best breeding values (the animals that would contribute best genes to next generation) to increase frequency of good genes

Mating - Selected males to be bred with selected females to change genotypic frequencies

Question 9

Gene Frequency

Answer 9

The gene frequency is the proportion of loci in a given
allelic series occupied by a particular gene.

There are N individuals and 2N alleles for a given locus.
What is the proportion of A or a alleles out of these 2N
alleles?

Question 10

Genotypic frequency

Answer 10

the proportion of the N
individuals in the population with a particular genotype.
What proportion are AA? What proportion are Aa?

Question 11

three method to select several traits

Answer 11

• tandem selection
• independent culling levels
• index selection

Question 12

What is index selection

Answer 12

• Involves calculating a total score for each animal
  
  • Add up the animal’s merit in each trait and arrive at a total score
• Most efficient of these three methods of selection
  
  • Results in maximum genetic improvement

Question 13

How do you obtain phenotypic variance

Answer 13

squaring the phenotypic standard deviations

Question 14

What is inbreeding coefficient F

Answer 14

Measure the intensity of inbreeding

F =  (1/2)^n+1  x  (1 + Fc)
n = the number of segregation (number of arrows or steps) from the sire back through the common ancestor to the dam
Fc = inbreeding coefficient for inbred common ancestor

Question 15

Generation interval

Answer 15

average age of a parent is able to provide the next generation