If a carrier haemophilic female (XHXh) is married to a haemophilic male (XhY). What will be the ratio of presence of haemophilia in the children. Select best answer from the given options.
Correct answer: C. Carrier female 25%, haemophilic female 25%, normal male 25%, and haemophilic male 25%
- A. 100% of all females and males will be haemophilic
- B. Females have a 50% chance of being haemophilic, and males will be 100% haemophilic
- C. Carrier female 25%, haemophilic female 25%, normal male 25%, and haemophilic male 25%
- D. Females and males both have a 50% chance of being haemophilic
Explanation
In the genetic cross between a carrier female (XHXh) and a haemophilic male (XhY), the possible genotypes of the offspring can be determined using a Punnett square. The resulting offspring can be:Carrier daughter: XHXhHaemophilic daughter: XhXhNormal son: XHYHaemophilic son: XhYThis results in four possible outcomes, each with an equal probability of 25%. Therefore, option C correctly describes this scenario.Option A is incorrect because it suggests all offspring will be haemophilic, which is not possible with the given genotypes. Option B is also incorrect as it implies all males must be haemophilic, which requires the mother to be XhXh. Option D simplifies the probabilities too much and does not accurately represent the distinct outcomes of the cross. Thus, option C is the most accurate representation of the ratios of haemophilia in the children.
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Mendel's laws explain segregation, independent assortment and the prediction of genetic ratios using alleles, genotypes and phenotypes. The chapter also covers linked genes, recombination and crossing over during meiosis, then applies pedigree reasoning to X-linked recessive traits, which show different inheritance patterns in males and females.
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