Varitation

Question 1

another term for variation

Answer 1

differences

Question 2

Basic types of variation

Answer 2

phenotypic variation and genetic variation

Question 3

refers to the actual variation we observe among animals for each trait of interest

Answer 3

phenotypic variation

Question 4

phenotypic variation

Answer 4

refers to the actual variation we observe among animals for each trait of interest

Question 5

what we can measure or touch

bonus: give examples

Answer 5

phenotype

bonus: growth rate, backfat depth, number of pigs born in a litter

Question 6

genes that make up an animal

Answer 6

genotype

Question 7

True or False:

Genotype does not contribute to phenotype

Answer 7

False, genotype contributes to the phenoype but many other factors also contribute to the phenotype (feeding, management, housing, disease, and other environmental factors)

Question 8

True or False:

observing the pheontype of an animal does not necessarily tell us much about its genotype

Answer 8

True

Question 9

Modify: (Provide two answers)

Genetic variation is the appearance or performance of the animal

Answer 9

Phenotypic variation is the appearance or performance of the animal

Genetic variation is the genetic make-up of the animal

Question 10

refers to the amount of variation that is controlled by genes

Answer 10

genetic variation

Question 11

what determines the potential amount of genetic improvement that can be made in a given breed or strain?

Answer 11

genes that are passed on from parents to offspring and the amount of genetic variation

Question 12

what are alleles?

Answer 12

different forms of the same gene

Question 13

different forms of the same gene

Answer 13

alleles

Question 14

traits that are controlled by alleles of a single gene

bonus: meaning?

Answer 14

categorical/qualitative genes

bonus: traits fall into clearly distinguishable categories (horned or not horned, black coat or red coat, etc.)

Question 15

_______________ can easily be fixed in the population so that no further genetic variation exists.

clue: for example, purebred Black Angus cattle are all black and show no variation for color

Answer 15

categorical/qualitative traits

Question 16

True or False:
Most economically important traits are qualitative

Answer 16

False, most economically important traits are quantitative

Question 17

quantitative traits (fall in categories / measured in a continuous scale)

bonus: give example

Answer 17

measured in a continuous scale

bonus: back fat, weaning weight, growth rate

Question 18

True or False:

quantitative traits are generally controlled by many genes

Answer 18

true

Question 19

__________________ are virtually impossible to eliminate genetic variation from a given population

bonus: why?

Answer 19

quantitative traits

bonus: because quantitative traits are generally controlled by many genes

Question 20

genetic variation is often attributed to different kinds of gene action

what gene actions?

Answer 20

additive gene action, dominance gene action, and epistatic gene action

Question 21

Differentiate phenotypic variation and genotypic variation

Answer 21

phenotypic variation
- refers to the actual variation observed among animals for each trait of interest
- appearance/performance of the animal

genetic variation
- refers to the amount of variation that is controlled by genes
- genetic make-up of an animal

Question 22

Differentiate qualitative and quantitative traits

Answer 22

Qualitative / Categorical traits
- controlled by alleles of a single gene
- falls into clearly distinguishable categories
- can be easily fixed in the population so that no further genetic variation exists

Quantitative traits
- most economically important traits
- controlled by many genes
- measured on a continuous scale
- virtually impossible to eliminate genetic variation from a given population

Question 23

Explain:

P = G + E

bonus: further expand the equation and explain

Answer 23

Genotype and environment (/ non-genetic factors) contribute to phenotype

bonus:
P = A + D + EG + E

genetic variation (hence, genotype) are often attributed to additive, dominace, and epistatic gene actions

Question 24

describes the summing up of effects of alleles of a gene and of effects of genes at a different chromosome locations to make up a trait

Answer 24

additive gene action

keywords to take note: sum and adding of effects of genes

Question 25

refers to one allele overriding or dominating another at the same locus

Answer 25

dominance gene action keyword: override and ominance of one allele

Question 26

True or False: dominance gene action is usually difficult to take advantage of in breeding programs and is often ignored except for a few single gene traits like coat colort

Answer 26

true

Question 27

refers to the interaction of different genes so that they tend to enhance or cancel each other out rather than adding together

Answer 27

epistatic gene action

Question 28

_____________ is the most important for genetic improvement since it can be influenced by selection programs

Answer 28

additive gene action

Question 29

true or false: dominance gene action contributes the most of the genetic variation behind most of the economically important traits

Answer 29

false, additive genetic action

Question 30

differentiate additive, dominance, and epistatic gene action

Answer 30

Additive Gene Action - describes the summing up of effects of alleles of a gene and of effects of genes at different chromosome locations to make up a trait - most important for genetic improvement since it can be influenced by selection programs - contributes most of the genetic varation behind most of the economiclly important traits Dominance Gene Action - refers to one allele overriding or dominating another at the same locus - usually difficult to take advantage of in breeding programs and is often ignored except for few single gene traits Epistatic Gene Action - refers to th interaction of different genes so that they tend to enhance or cancel each other out rather than adding together

Question 31

ratio of genetic variation to phenotypic variation

Answer 31

heritability

Question 32

heritability tells us what proportion of the differences in performance we observe between animals is due to _________ which can be passed on from generation to generation; and the remaining proportion is due to _______________ which cannot be passed on from generation to generation.

Answer 32

gene action; environmental and outside influences

Question 33

heritability is the ratio of genotypic variation to phenotypic variation give the equation for heritability

Answer 33

h^2 = genetic variance / phenotypic variane

Question 34

heritability value range from _________

Answer 34

0 to 1 or 0% to 100%

Question 35

True or False: low heritability value means that genes has low genetic control over the trait bonus: meaning?

Answer 35

true bonus: meaning trait is not easily heritable

Question 36

moderate value for heritability

Answer 36

0.3 - 0.5 (30% - 50%)

Question 37

given trait B and b BB is _______ while Bb is _______

Answer 37

BB - homozygous Bb - heterozygous