Complex Patterns of Inheritance

Complex Patterns of Inheritance

Sometimes two traits can be dominant at the same time

Whats the difference between incomplete dominance and co-dominance?Incomplete Dominance: Complex inheritance pattern in which the heterozygous phenotype is intermediate between those of the two homozygous parent organismshuh?RRWW

RW

RW

RW

RWMixes like paint!

Whats the difference between incomplete dominance and co-dominance?Co-Dominance: Complex inheritance pattern that occurs when neither allele is dominant and both alleles are expressed.BBWWBWBWBWBW

Multiple AllelesInheritance that involves more than 2 alleles for a traitEx: Blood types!

ABO Blood Groups AllelesType A: IAType B: IBType O: i

i recessive to IA & IBIA & IB codominant with each other

Multiple Alleles Lets list all the possible genotypes for each blood type.

Human Blood Group GenotypesA: IAIA (homozygous dominant) or IAi (heterozygous)

B: IBIB (homozygous dominant) or IBi (heterozygous)

AB: IAIB (co-dominant)

O: ii (homozygous recessive)

Sex DeterminationSex chromosomes 1 pair of your 232 types : X and YXX: femaleXY: male(the other 22 pairs of chromosomes are autosomes)

X-linked Genes (Sex-linked)An allele inherited on the X chromosomeX-linked recessive: more males are affected than femalesFemales have 2 Xs 1 likely to be normal, mask the effectXHXh (Carrier female)Males have 1 X if he gets the bad allele, he has the disorder for sureXhYPolygenic InheritanceMany gene pairs act together to produce a single traitExamples: skin color, fingerprints, height

Polygenic TraitsMore intermediate phenotypes than extremes (Example: Height)

KaryotypeMicrograph showing pairs of homologous chromosomes22 matching autosomes and pair of sex chromosomes

Review from last unit: NondisjunctionChromosomes fail to separate properly during meiosisGamete does not have correct # of chromosomes Results in zygote with too many or few chromosomes3 copies trisomy1 copy monosomy

Nondisjunction

Down SyndromeTrisomy 21 3 copies of chromosome 21Distinct facial features, heart defects, mental disabilitiesFrequency increases with age of mother1 out of 800 in born in US

Which person has Down Syndrome?