chp 2 extension to mendels laws

what is incomplete dominance

when an offspring does not resemble either homozygous parent but has a phenotype that is an intermediate between the two pure breeding parents.

what is codominance

when an offspring shows both homozygous parents traits in a new phenotype

what is dominance series

the order of alleles most dominant to least dominant

what is allele frequency, how is it calculated

proportion of a particular allele in a population, calculated by alleles in question / total alleles

what is a wild type allele

a common allele in the natural population, allele freq over 1%

what is a mutant allele

a rare or new allele

what is a monomorphic gene

a gene with only one wild type allele. aka, every individual in a population only has one allele for a specific gene

what is a polymorphic gene

a gene that has multiple wild type alleles

what are high frequency alleles of a polymorphic gene called

common variants

what is pleiotropy

when a single gene determines multiple traits

define a syndrome

A group of genetic problems usually seen together

what is a recessive lethal allele

an allele that affects both phenotype and viability, prevents the survival of a homozygote

describe additive interactions

when two genes interact with each other to produce trait phenotype

what is a novel phenotype

a brand new phenotype not seen in parents that arises from additive interactions

what is epistasis

interaction between alleles of different genes in which one genes phenotype mask another genes phenotype

in the context of epistasis, what is the term for gene that does the masking

epistatic

in the context of epistasis, what is the term for gene who’s phenotype is masked

hypostatic

what is recessive epistatis

when a recessive homozygote masks phenotype of another gene

explain how recessive epistasis happens

when a certain biochemical process is blocked or cannot happen by the absence of a specific protein or enzyme due to a recessive homozygote

what is dominant epistasis

when a dominant homozygote masks phenotype of another gene

explain dominant epistasis

when a dominant allele creates a block or does not create the needed protein or enzyme for a certain event to occur

what is a heterogeneous trait

a recessive phenotype caused by mutations in different genes

locus heterogeneity

property of a trait where mutations in any one of two genes results in the same mutant phenotype

what is complementation, give an example

when an offspring of parents with the same homozygous recessive mutation from different genes is wild type. Two deaf parents that are homozygous recessive at different genes have a hearing child .

what does 9:3:3:1 ratio indicate about two genes in question

they function in independent pathways and alleles interact additively

what are complex traits

traits controlled by the interactions of multiple genes that are polygenic and often multifactorial

what is penetrance

proportion of individuals with a particular genotype that show the associated phenotype

what is complete penetrance

all individuals who have the genotype show the associated phenotype

incomplete penetrance

all individuals with the genotype will not always show associated phenotype

variable expressivity

individuals with the same genotype may show associated phenotype but to different degrees

unvarying expressivity

individuals with the same genotype may show phenotype but will be in the same way

what is a modifier gene

genes that have a secondary or subtle effect on teh phenotype

explain why siamese cats are different colous on their extremities

their enzyme for coat colour is temperature sensitive and produces melanin in cooler temps rather than warmer temps

What is a conditional lethal allele

an allele that will be lethal under specific conditions

what are continuous or quantitative traits

traits that show a measurable variation between two extremes, most are polygenic