Varitation Flashcards
another term for variation
differences
Basic types of variation
phenotypic variation and genetic variation
refers to the actual variation we observe among animals for each trait of interest
phenotypic variation
phenotypic variation
refers to the actual variation we observe among animals for each trait of interest
what we can measure or touch
bonus: give examples
phenotype
bonus: growth rate, backfat depth, number of pigs born in a litter
genes that make up an animal
genotype
True or False:
Genotype does not contribute to phenotype
False, genotype contributes to the phenoype but many other factors also contribute to the phenotype (feeding, management, housing, disease, and other environmental factors)
True or False:
observing the pheontype of an animal does not necessarily tell us much about its genotype
True
Modify: (Provide two answers)
Genetic variation is the appearance or performance of the animal
Phenotypic variation is the appearance or performance of the animal
Genetic variation is the genetic make-up of the animal
refers to the amount of variation that is controlled by genes
genetic variation
what determines the potential amount of genetic improvement that can be made in a given breed or strain?
genes that are passed on from parents to offspring and the amount of genetic variation
what are alleles?
different forms of the same gene
different forms of the same gene
alleles
traits that are controlled by alleles of a single gene
bonus: meaning?
categorical/qualitative genes
bonus: traits fall into clearly distinguishable categories (horned or not horned, black coat or red coat, etc.)
_______________ 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
categorical/qualitative traits
True or False:
Most economically important traits are qualitative
False, most economically important traits are quantitative
quantitative traits (fall in categories / measured in a continuous scale)
bonus: give example
measured in a continuous scale
bonus: back fat, weaning weight, growth rate
True or False:
quantitative traits are generally controlled by many genes
true
__________________ are virtually impossible to eliminate genetic variation from a given population
bonus: why?
quantitative traits
bonus: because quantitative traits are generally controlled by many genes
genetic variation is often attributed to different kinds of gene action
what gene actions?
additive gene action, dominance gene action, and epistatic gene action
Differentiate phenotypic variation and genotypic variation
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
Differentiate qualitative and quantitative traits
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
Explain:
P = G + E
bonus: further expand the equation and explain
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
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
additive gene action
keywords to take note: sum and adding of effects of genes
refers to one allele overriding or dominating another at the same locus
dominance gene action
keyword: override and ominance of one allele
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
true
refers to the interaction of different genes so that they tend to enhance or cancel each other out rather than adding together
epistatic gene action
_____________ is the most important for genetic improvement since it can be influenced by selection programs
additive gene action
true or false:
dominance gene action contributes the most of the genetic variation behind most of the economically important traits
false, additive genetic action
differentiate additive, dominance, and epistatic gene action
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
ratio of genetic variation to phenotypic variation
heritability
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.
gene action;
environmental and outside influences
heritability is the ratio of genotypic variation to phenotypic variation
give the equation for heritability
h^2 = genetic variance / phenotypic variane
heritability value range from _________
0 to 1 or 0% to 100%
True or False:
low heritability value means that genes has low genetic control over the trait
bonus: meaning?
true
bonus: meaning trait is not easily heritable
moderate value for heritability
0.3 - 0.5 (30% - 50%)
given trait B and b
BB is _______ while Bb is _______
BB - homozygous
Bb - heterozygous
