Lecture 9 - Gathering Variability Flashcards
which generation has the most genetic variability and which has least (assuming parents where homozygous)
F2 has lots of genetic variability, F1 has none
t/f: crosses with multiple parents generate a F1 population with lots of genetic variability
t
how many f1 seeds do you need from a single cross
depends on how many you need to achieve target population and the type of species
pedigree
description of crosses made to develop a cultivar
natural selection is _____ happening
always
artificial selection is imposed by ________
the breeder
how is artificial selection imposed by the breeder
by saving the seed from the best plant or throwing away the worst
selection
choosing plants with the most desirable characteristics
what happens to allele and genotypic frequencies with selection
allele - increase frequency of desired alleles
genotype - less amount of genotypes
how to define the best plant
based on objectives and genetic vs. environmental variation
why are phenotypes not always representative of the genotype
gene action
gene action
how genes interact and influence each other in the genome
types of gene action
additive, dominance, or epistatic (or additive vs. non additive)
epistasis
the allele of the one gene in the genotype suppresses the effect of an allele of another gene on the phenotype (one masks another)
difference between dominance and epistasis
dominance: intra-allelic gene interaction where A dominates over a
epistasis - inter-allelic gene interaction where AA dominates over BB
mendels 2nd law
alleles of different genes segregate independently from each other
additive gene influence
alleles of both gene influence the same phenotype
why do changes in allelic frequency happen more rapidly in selfing species
it is random, so it is difficult to remove (MIGHT BE WRONG)
response to selection
change in population mean from selection
what is heritability/h2
a function of the amount of total variability due to genetic causes
2 types of heritability
broad-sense H2 (Vg/Vp)
narrow sense h2 (Va/Vp)
which type of heritability estimate is the most valuable to the plant breeder
narrow sense heritability
why are heritability estimates important to breeders
- response to selection is related to heritability (higher means phenotype is close to genotype = better selection)
- determines when selection should commence (higher means less environmental effect)
- which selection method to use
- shows resources needed
High heritability = _____ - ______
0.75 - 1.0
moderate heritability = _____ - _____
0.5 - 0.75
low heritability = <_____
0.5
