I need help
Dear Anna,
Hemophilia is a rare genetic disorder in which the blood does not clot properly. This means that after an injury, a person who suffers from hemophilia bleeds more than someone without hemophilia. This bleeding can damage the organs and tissues of the individual and may be life threatening.
4 a) Haemophilia is more likely to occur in males than females. Because females have two X chromosomes and its rare chance for a female to have two defective copies of the gene so females are almost exclusively asymptomatic carriers of the disorder. But males have one X chromosome, which if defected definitely causes a disorder. Therefore, the pattern is that females will always be carrier (if father is affected) and sons (1/2) will also be affected (when their is carrier).
ii) From the third generation, as mother is a carrier, she will always pass on the trait to her sons (where 1/2 of them) will be affected. (As males have only one X chromosome, therefore, they are affected).
4 b) It is an X-linked recessive trait.
The explanation is as follows:
The term X-linked recessive trait refers to the condition in which the gene controlling a specific trait is present in its recessive form on the X-chromosome. You might be knowing that humans have 23 pairs of chromosomes, out of which 22 are autosomes and the one pair is sex chromosomes. Males have 22+XY chromosomes while females have 22+XX chromosomes. If any trait is recessive, then two copies of the gene is required for its expression. One such example for X-linked recessive trait is the gene coding for the disease haemophilia. Haemophilia is a congenital disease (hereditary disease) that is caused by the deficiency of Factor VIII, an important clotting factor. The mutation in this gene leads to this deficiency. The gene for this factor is carried on the X-Chromosome. This gene appears in the normal (dominant) and the mutant (recessive form). Because females have two X chromosomes while males have only one X chromosome, for a female to get affected by haemophilia she has to have the mutant gene on both the X chromosomes while males may be affected if the carry it on the one X chromosome. Moreover, haemophilia in females is lethal condition and these females may not survive past their childhood.
All the best
Regards
Hemophilia is a rare genetic disorder in which the blood does not clot properly. This means that after an injury, a person who suffers from hemophilia bleeds more than someone without hemophilia. This bleeding can damage the organs and tissues of the individual and may be life threatening.
4 a) Haemophilia is more likely to occur in males than females. Because females have two X chromosomes and its rare chance for a female to have two defective copies of the gene so females are almost exclusively asymptomatic carriers of the disorder. But males have one X chromosome, which if defected definitely causes a disorder. Therefore, the pattern is that females will always be carrier (if father is affected) and sons (1/2) will also be affected (when their is carrier).
ii) From the third generation, as mother is a carrier, she will always pass on the trait to her sons (where 1/2 of them) will be affected. (As males have only one X chromosome, therefore, they are affected).
4 b) It is an X-linked recessive trait.
The explanation is as follows:
The term X-linked recessive trait refers to the condition in which the gene controlling a specific trait is present in its recessive form on the X-chromosome. You might be knowing that humans have 23 pairs of chromosomes, out of which 22 are autosomes and the one pair is sex chromosomes. Males have 22+XY chromosomes while females have 22+XX chromosomes. If any trait is recessive, then two copies of the gene is required for its expression. One such example for X-linked recessive trait is the gene coding for the disease haemophilia. Haemophilia is a congenital disease (hereditary disease) that is caused by the deficiency of Factor VIII, an important clotting factor. The mutation in this gene leads to this deficiency. The gene for this factor is carried on the X-Chromosome. This gene appears in the normal (dominant) and the mutant (recessive form). Because females have two X chromosomes while males have only one X chromosome, for a female to get affected by haemophilia she has to have the mutant gene on both the X chromosomes while males may be affected if the carry it on the one X chromosome. Moreover, haemophilia in females is lethal condition and these females may not survive past their childhood.
All the best
Regards