11.2 COMPLEX PATTERNS OF INHERITANCE REFLECT simple dominance--traits are either dominant or recessive CONSIDER traits such as height OBSERVE differences in height: shortest to tallest HYPOTHESIZE: is height simple dominance?

MENDEL’s EXPERIMENTS -ALL 7 traits were simple dominance -ALL 7 traits were inherited independently EXCEPTIONS TO MENDEL’S LAWS -INCOMPLETE DOMINANCE -CO-DOMINANCE -SEX LINKAGE -MULTIPLE ALLELES -POLYGENIC TRAITS  Complex Inheritance of Traits do NOT follow Inheritance Patterns Mendel Described

 INCOMPLETE DOMINANCE INCOMPLETE DOMINANCE -”blended” traits Heterozygous genotype results in “mixture” of the 2 traits R=red r=white then Rr = pink R R R r rrrr RrRr Rr RR Rr Rr rr 100% pink 25% red/50% pink/25% white *different amounts pigment— R most  r least

 INCOMPLETE DOMINANCE

 CODOMINANCE CODOMINANCE-”both” traits present in heterozygous R=red cow r=white cow Rr=roan cow (red & white) R R R r rrrr RrRr Rr RR Rr Rr rr 100% roan 25% red/50% roan/25% white *roan—BOTH red & white hairs

 CODOMINANCE

Sickle cell: BB-normal Bb=both bb=sickle cell

 SEX DETERMINATION 23 rd pair chromosomes determine gender XX = XY = FEMALE MALE X y XXXX XX Xy 50%

 SEX LINKED TRAITS -Genes are carried on the sex chromosomes -Sex-linked genes on X chromosome ONLY – X B X B normal female – X B X b carrier female – X b X b affected female – X B Y normal male – X b Y affected male

 SEX LINKED TRAITS— “X-LINKED” SEX CHROMOSOMES—some genes only on larger X chromosome, NOT on the smaller y chromosome X B = dominant trait X b = recessive trait Red-green color-blindness w/parents not CB (mom hetero) males---- X b y50% CB females— X B X b 0% CB *8% males have red-green CB rare in females X B y XBXbXBXb X B X B X B y X B X b X b y

 SEX LINKED TRAITS— “X-LINKED” X b y X B X b X B Y X b X B X b X B y X b X b X b Y X B X b X b y X B X b X b Y 50% girls CB/50% boys CB 0 girls CB/100% boys CB

Exceptions to Mendel’s Laws Sex Linkage

Sex linked Inheritance in Drosophila

 MULTIPLE ALLELES More than 2 possible alleles for a trait ABO BLOOD TYPES I A I B i IAIA IBIB i I A I A I A I B I A i -A- -AB- -A- I A I B I B I B I B i -AB- -B- -B- I A i I B i ii -A- -B- -O- PHENOTYPE/GENOTYPES A I A I A, I A i B I B I B, I B i AB I A I B O ii

 MULTIPLE ALLELES Blood Group (Phenotype) O Genotypes Antibodies Present in Blood Reaction When Blood from Groups Below Is Mixed with Antibodies from Groups at Left OABAB A B ii I A or I A i I B or I B i I A I B Anti-A Anti-B Anti-A

 MULTIPLE ALLELES I A I B i I A i I B i I A I B I B i I A i ii I A i I B i AB / B / A / O 50% A / 50% B

 HIEARCHY OF DOMINANCE IN ALLELES -heirarchy of dominance in multiple alleles Example: rabbit coloring C-full coat colorall black C ch -chinchilablended C h -himilayanspots c-albinowhite Order of dominance— C > C ch > C h > c

 POLYGENIC TRAITS MELANIN leastmost aabbcc AaBbCc AABBCC

 POLYGENIC TRAITS- HAIR COLOR

-WHAT POSSIBLE EYE COLORS ARE THERE? -blue, green, brown  EXAMINE EACH OTHER’S EYES -What else do you notice about eye color? HYPOTHESIZE: Is eye color inherited in a simple dominant/recessive manner -exact inheritance not determined -polygenic models have been made THINK –PAIR- SHARE

 POLYGENIC TRAITS- EYE COLOR

 POLYGENIC TRAITS HETEROCHROMIA IRIDIUM—2 different color eyes Can result from trauma to the eye Can be a altered gene