Variations on Mendel

1. INCOMPLETE DOMINANCE Neither trait is completely dominant over the other Get a BLEND of the two traits The new phenotype is somewhere between the original two

W = white R = Red White Carnation x Red Carnation Parent Genotypes? –WW x RR Do the Punnett Square What do you get????

WW R R WR WR = 4 / 4 are pink carnations

What happens if you cross 2 Pink Carnations? –WR x WR –Do the Punnett Square –What phenotypes occur?

WR W R WWWR RR WW = 1 / 4 white WR = 2 / 4 pink RR = 1 / 4 red

Another Incomplete Dominance example….. White bunny x brown bunny = ?? WW x BB = WB WB = tan WB W W B B

2. CODOMINANCE Two traits are dominant at the same time Both traits are fully expressed at the same time

EX: Speckled Chickens These birds have BOTH black and white feathers Both black and white are dominant

BB = black feathers WW = white feathers BW = speckled Cross a black with a speckled- -what are possible phenotypes?

BB B W BB BW BB = 2 / 4 black BW = 2 / 4 speckled

Blood Type: based on 2 gene groups (1)ABO: --Two dominant genes ( I A and I B ) --One recessive gene ( i ) –Genotype of I A I B makes phenotype of ___ (codominant) – I A i or I A I A makes _________ – I B i or I B I B makes __________ – i i makes __________

Can a Type A and a Type B have a: –Type AB child? Yes –Type A child? Yes..if Type B parent is I B i –Type B child? Yes…. if Type A parent is I A i –Type O child? Yes…if both are heterozygous

Blood Type: based on 2 groups of genes (2) Rh Factor: -- One dominant gene (Rh+) -- One recessive gene (Rh-) I A i Rh+ Rh- makes _________ I B i Rh+ Rh+ makes __________ i i Rh- Rh- makes __________

3. MULTIPLE ALLELES –Genes that have more than just one dominant and one recessive allele –Ex: Blood type –Ex: Rabbit Coat Color (see pg. 273) Full, chinchilla, himalayan, albino

4. POLYGENIC TRAITS Trait controlled by more than one gene “poly” = many EX. Skin color-controlled by 4 different genes EX: Hair Color, Height, Weight

Section 11-5: Gene Maps Gene Map: shows location of each gene on a chromosome EX: fruit fly chromosome #2: pg. 280 Gene Linkage: genes on the same chromosome are usually “linked” together--they are passed on together –Ex: blue eyes / blonde hair