Make a Punnett square for the following test cross: A black hamster of unknown genotype is crossed with a white hamster (aa). The offspring are 50% white. What was the genotype of the unkown black hamster?

Dominance relationships

Heterozygotes have a mixed phenotype Aa = pink

Both genes are expressed Aa = spotted

 More than 2 alleles of a gene  4 genes for rabbits  C=agouti C ch =chinchilla C h =himalayan c=albino  Dominance C > C ch > C h > c

One allele hides the other One gene needed to “turn on” another gene B = dark pigment b = light pigment E gene needed for color eebb= yellow fur Eabb= chocoalte fur Analyzed with a dihybrid cross

Trait controlled by many genes Continuous range of phenotypes

Internal Hormones External Temperature, nutrition, etc.

Thomas Hunt Morgan Used fruit fly XX=female, XY= male Gene on X chromosome Males XY Often have disease Females XX Often carriers (heterozygous) Passed from mothers to sons “Skips a generation”

X R X R X r X R Y

11 Single allele traits (dominant) Huntington ’ s disease, dwarfism, cataracts Single allele traits (recessive) Albinism, cystic fibrosis, hereditary deafness Polygenic traits Hair/skin/eye color, foot size, nose length, height X-linked traits Colorblindness, hemophilia, muscular dystrophy Multiple allele traits ABO blood groups

12 Three alleles control blood type: I A, I B, i Blood types are: A, B, or O GenotypeBlood Type IAIAIAIA A IAiIAiA IBIBIBIB B IBiIBiB IAIBIAIB AB iiO

If A is blue and a is yellow, what will Aa be if there is incomplete dominance? If there is codominance? An X A X a female (normal) mates with a colorblind (X a Y) male. What percentage of male offspring will be colorblind? Female offspring?

14 Punnett squares are helpful, but provide only information on one generation at a time Pedigree analysis provides a pattern of inheritance within a family grouping Phenotypes of family members are studied Rules for making a pedigree 1.) Circles are females; squares are males 2.) Horizontal lines represent marriage unions or linkage between brothers & sisters 3.) Vertical lines represent offspring; offspring in order L  R oldest  youngest 4.) Filled in = infected, ½ filled in = carrier

Given the pedigree to the left… How many males are colorblind? How many females are colorblind? How many females are carriers? How many married couples are shown?