genetics lec19

expression of most traits

controlled by interaction of several genes and multiple nongenetic factors

for most genes…..

there are many alleles present in the population

many genes…..

show incomplete dominance, codominance, epistasis, and other nonmendelian relationships

mitochondria and chloroplasts

have their own dna and their genes make proteins that influence many phenotypic traits

some genotypes are lethal….

which distorts the expected ratios of genotypes and phenotypes in the offspring

genetic maternal effect

the copy of gene that gets inherited from dad is silenced so only mom’s genotype influence phenotype

imprinted genes

only one copy of imprinted gene is active, for each imprinted gene everyone silences the same copy either maternally derived or paternally derived in every cell

uniparental disomy

inheritance of both members of chromosome pair from the same parent

the degree of allelic diversity present in most genes

different gene allele may produce different protein isoforms with different levels of activity

dominance hierarchy

multiple alleles means there are more phenotypes where one is dominant over another which is dominant over another

incomplete dominance

neither phenotypic trait is fully expressed in the offspring

codominance

both phenotypic traits are fully expressed, ex is ab bloodtype

many allele interactions …………….

creates novel phenotypes that may not lie on the same continuum as parental phenotype

some allele combinations….

may be lethal

gene activity influenced by temperature

some genes may only be expressed in cold parts of the body and not warm

epistasis

suppression of the effect of a gene by another gene

epistatic/ dominanting gene

the gene masking the effect of another gene

regulated/ hypostatic gene

gene whose functionality of expression is masked

dominant epistasis

individual with one or more copies of dominant allele for the epistatic gene, it doesn’t matter what alleles the individual has at other gene

recessive epistasis

the individual has homozygous recessive genotype for the epistatic gene, it doesn’t matter what alleles the individual has at the other gene

duplicate recessive epistasis

occurs when you mate two people with recessive trait but are homozygous for the recessive alleles of the two different genes, the offspring will exhibit dominant trait

allelic disorders

different mutations in the same gene produce effects on the childs phenotype that are variable

sex influenced characteristics

individuals sex can influence phenotypic effects of gene alleles

sex limited characteristics

never appear in one sex, the gene mutations have zero penetrance in that sex

maternal effect genes

offsprings phenotype is determined by the mothers genotype by both alleles the mother has

mitochondrial inheritance is matrilineal

we inherit all our mitochondria from our mothers, affected females have affected children and affected males don’t

Uniparental disomy

heterodisomy

the child has one copy of each of the two chromosomes the parent has

Uniparental disomy

isodisomy

the child has two copies of one of the chromosomes the parent has

how does uniparental disomy occur

heterodisomy results from nondisjunction during meiosis one of anaphase one

how does isodisomy occur

nondisjunction during meiosis two of anaphase two