Special Crosses II: Blood and Sex-Linked

What are multiple alleles? Multiple Alleles: when two or more alleles contribute to the phenotype. Example- Human blood types (I) are determined by three alleles I A I B ii I AB A, B, O & AB A and B are codominant with each other. BUT both A & B are dominant over O.

ii universal donorO only I A I B AB only universal recipient I A I A A or OA or AB I A i I B I B B or O B or AB I B i

How common are the different blood types?

Example: A man with type AB blood marries a woman with type B blood whose father has type O blood. Give the expected phenotypic and genotypic ratios for their children. Example: A man that is heterozygous for type B blood marries a woman who is heterozygous for type A blood. What blood types will their children potentially have? Example: A man is accused of fathering two children, one with type O blood and another with type A blood. The mother of the children has type B blood. The man has type AB blood. Could he be the father of both children? Explain your answer.

What are Sex-Linked Traits? Sex-Linked Traits: trait carried by a sex chromosome, especially an X chromosome, X much larger than Y Every living organism has 46 chromosomes in autosome or somatic cells (body cells). 2 of those 46 are sex chromosomes.

What’s sex got to do with it? an organism’s sex can affect the chances of inheriting a gene Most sex-linked genes are found the X chromosome. Why? X is much larger.

Hemophilia Blood clotting disorder X-linked Recessive

Color Blindness