Explain inheritance of haemophilia
Answers
Answer:
HEMOPHILIA
Explanation:
Hemophilia A and hemophilia B are inherited in an X-linked recessive pattern . The genes associated with these conditions are located on the X chromosome, which is one of the two sex chromosomes . In males (who have only one X chromosome), one altered copy of the gene in each cell is sufficient to cause the condition.
Haemophilia haemophilia is a defect of blood which prevents its clotting.Haemophilic persons bleed excessively when injured . It is caused by a reccesive gene (h) located in the X chromosome.
This recessive gene loses its ability to produce the coagulent.
Man has one X chromosome and one Y chromosome . The gene for haemophilia is located in the X chromosome is able to produce the defect because there is no homologue of this gene in the Y chromosome to check its expression.
Woman has two X chromosomes . For her to be haemophilic , it is necessary for both the X chromosomes' gene to be haemophilic. Such feamales are not born as the combination of two reccesive gene is fatal.
If only one X chromosome bears a gene for haemophilia , its dominant homologous gene in the other X chromosome will check the expression of the reccesive gene. Such females are carriers.
The three cases are discussed in the attachment :-
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• These are chromosome pairs of approximately same length, centromere position and staining pattern, with genes for the same characteristics at the corresponding loci
• In an organism, one homologous chromosome is inherited from mother and other from the father .
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