ometaa recessive doder Crom man oomal for blood detting and a woman whe is a camer of the condition 15 The genes for hemophilia, a condition that causes blood not to det property, are located on the X Man Gametes Genotype Phenotype Woman Gametes Genotype Phenotype Punnett square Genotype ratio Phenotype ratie 16 colorbilindnes isa recenive tralt carried on the X chromosome. Cross a colorbilind male with a female with no history of colorblindnes in her family Man Gametes Genotype Phenotype Woman Phenotype Gametes Genotype Punnet square
Human inheritance is studied by the technique known as pedigree analysis. Pedigree analysis is used to study the five types of inheritance patterns in humans. The patterns are autosomal dominant, autosomal recessive, X-linked dominant, X-linked recessive, and Y linked traits. Red-green color blindness and Hemophilia in humans are due to an X-linked recessive gene.
Characteristics of the X-linked recessive trait.
- More males are affected than females.
- The trait skips generations.
- Approximately half of the carrier mother's sons are affected.
- It is never passed from father to son
- All daughters of the affected father are carriers.
Haemophilia is an X linked recessive trait located in humans.
A normal male is crossed with a carrier female. Let XH be the allele for normal blood clotting factor and Xh be the allele for haemophilia. The normal male is hemizygous and will have only one X chromosome which is a normal blood clotting factor XH. The female is a carrier so the genotype will be XH Xh and will produce two types of gametes. The male transfers the only X chromosome it has to a daughter while the mother will transfer either of one chromosome.
| XH | Xh | |
| XH | XH XH | XH Xh |
So the genotype of the daughter will be XH XH or XH Xh in the ratio of 1:1. The phenotype will be normal blood clotting factor in all the daughters.
The male never transfers the X chromosome to the daughter and the female can transfer either of the X chromosomes.
So the genotype of the son can be XH AND Xh in the ratio 1:1. The phenotype is normal clotting factor to the haemophilia disease in 1:1 ratio.
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