Alleles

1. Alleles • Two alleles for each gene • Half from your mom and half from your dad • A capital letter for dominant allele and a lower-case letter for the recessive allele • Dominant allele takes over a recessive allele • Recessive produces only when its paired allele is identical • The dominant chromosome is represented as XH • The recessive chromosome is represented as Xh

2. HemophiliaPunnett Squares XH Y • Punnett squares are used to show the probability of receiving a genetic disorder from a parent. XH XHXH XHY XHXh XhY Xh Xh Y Xh Y XH XHXh XHY XH XHXh XHY XH XHXh XHY XhXh XhY Xh Male w/ hemophilia and female non-carrier Male w/ hemophilia and female carrier Normal Male and female carrier

3. Punnett Square Probability Ratios: 2: 2: 2 XHXh 2 XHY Percentages: 50%: 50%: 50% XHXh 50% XHY Xh Y XH XHXh XHY Male w/ hemophilia and female non-carrier XH XHXh XHY

4. Punnett Squares Genotypes and Phenotypes • What do the letters mean ? • Uppercase letters represent dominant genes • Lowercase letters represent recessive genes • H is the dominant allele • h is are the recessive allele Xh Y Phenotype/What We See H = Normal Hh = Hemophilia Carrier XH XHXh XHY Male w/ hemophilia and female non-carrier XH XHXh XHY Genotype/What Is In Our Genes H is the Homozygous dominant Hh is the heterozygous dominant