Module 4 Quantitative inheritance Flashcards
Quantitative trait: ____
gradation from one phenotype to the next; continuum of phenotypes
* examples: growth rate, crop yield, weight
In general, their values in a population follow the NORMAL DISTRIBUTION
Continuous trait
Quantitative trait: ____
- phenotype falls into discrete, integral categories; discontinuous
- examples: ability to roll tongue, litter size in cats
include those which are of the and/or type like hairline can be widow’s peak or straight, earlobes can be attached
meristic trait
Quantitative trait: ____
threshold trait
- only 2 or a few phenotypic classes, but their inheritance is determined by multiple genes and environment
- expression implies affected individuals has liability over the threshold
underlying quantitative distribution, but the trait appears only if a threshold is crossed
- examples: diabetes, schizophrenia, certain cancers
All of the factors which influence the development of a polygenic disorder, whether genetic or environmental, can be considered as a single entity known as ____
LIABILITY
____ – any group of non-allelic genes, each having a small quantitative effect, that together produce a wide range of phenotypic variation;
- also called multiple factor, quantitative gene.
The loci act in concert in an additive fashion
Polygene
➢ additive variance (VA)
➢ dominance variance (VD) and
➢ epistatic variance (VI).
Together, the values for each of these subcategories yield the total amount of ___ responsible for a particular phenotypic trait.
genetic variation (VG)
represents the cumulative effect of individual loci; therefore, the overall mean is equal to the summed contribution of these loci.
Additive variation (VA)
represents interaction between alleles.
If a trait is controlled by a dominant allele, then both homozygous and heterozygous individuals will display the same phenotypic value.
Dominance variation (VD)
All instances of phenotypic variance (VP) within a population are the result of ___and/or ___
genetic sources (VG)
Environmental sources (VE).
The total phenotypic variation of a population (VP) is the sum of the variation in ____
additive (A),
dominance (D),
gene-interaction (I),
environmental (E)
gene-environment interaction (GE)
The total phenotypic variation of a population (VP) is the sum of the variation in ____
additive (A),
dominance (D),
gene-interaction (I),
environmental (E)
gene-environment interaction (GE)
Meaning:
VA =
VD =
VI =
VGE =
VA = Expression of a trait IS NOT controlled by the other allele at the locus.
VD = Expression of a trait IS affected by the other allele at the locus.
VI = Expression of a trait is affected by alleles at another loci.
VGE = A given genotype is superior to another in one environment
(differential local adaptation).
Plant and animal breeders should know:
* how much of the ____ of a trait is due to genetic variance
* how much is due to ___factors. This will give the breeder an idea on how to improve the quality of the products.
phenotypic variability
non-genetic environmental
Theoretically, any phenotypic differences between monozygotic twins are ____, because we know that they share the most similar genome.
environmental
