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Blood Types and Sex-linkage

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Presentation on theme: "Blood Types and Sex-linkage"— Presentation transcript:

1 Blood Types and Sex-linkage

2 Human Blood Types Human Blood Types have a gene that displays multiple alleles and codominance The gene has three alleles: A codes for an A antigen (protein) on red blood cells B codes for a B antigen (protein) on red blood cells O codes for no antigen on red blood cells

3 The A and B alleles are codominant
O allele is recessive

4 Blood Type Phenotypes and Genotypes
Phenotypes Genotypes Type A blood AA or AO Type B blood BB or BO Type AB blood AB Type O blood OO

5 Blood Type Antigens

6 Sex-linked Genes Sex-linkage
Gene for trait is found on a sex chromosome Most (almost all) are found on the X chromosome; there are very few Y-linked disorders Can be sex-linked dominant or sex-linked recessive

7 Inheritance of X-linked recessive disorder

8 Inheritance of X-linked recessive disorder

9 X-linked Genotypes and Phenotypes
Genotypes of each parent are written as superscripts on their sex chromosomes Ex: H=“healthy” allele; h= hemophilia allele XHXh female carrier of hemophilia XHXH female w/o hemophilia XhXh female with hemophilia XHY male w/o hemophilia XhY male with hemophilia

10 Sex-linked Punnett Squares

11 Hemophilia Punnett Square
Hemophilia is x-linked recessive

12 Color blindness (X-linked recessive)

13 X-linked Recessive Disorders
Show up more in males Females have two X chromosomes rare to inherit two “bad” X’s to show disorder One “good” X masks the “bad” X; healthy dominant allele masks the recessive allele Male have only one X chromosome Males only need one recessive allele to show the trait b/c they don’t have another X which could carry a healthy dominant allele to mask the recessive allele.

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