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Special Crosses II: Blood and Sex-Linked

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

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Special Crosses II: Blood and Sex-Linked

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  1. Special Crosses II: Blood and Sex-Linked

  2. 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 • IA IB ii IAB • A, B, O & AB • A and B are codominant with each other. • BUT both A & B are dominant over O.

  3. ii universal donor O only IAIB AB only universal recipient IAIA A or O A or AB IAi IBIB B or O B or AB IBi

  4. How common are the different blood types? 45 % 40 % 4 % 11 %

  5. 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.

  6. 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.

  7. 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.

  8. Hemophilia Blood clotting disorder X-linked Recessive

  9. Color Blindness

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