A man has a condition called hypophosphatemia, an electrolyte disorder in which there are low levels of phosphate in the blood. When investigating his family tree, he finds that his condition appears to be inherited but never passes from father to son. Which of the following types of disorder does he likely possess? Somatic. X-linked dominant. X-linked recessive. Y-linked.
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The condition hypophosphatemia is inherited but does not pass from father to son. This suggests that the gene responsible for the condition is not located on the Y chromosome, as Y-linked disorders would pass from father to son. Show more…
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Hypophosphatemia causes a deficiency of phosphates in the blood. Affected males pass on the disease to all their daughters and none of their sons. Affected females pass the disease on to about 50% of their children of both sexes. Assuming the above affected individuals married healthy individuals, identify the most likely inheritance pattern of this disorder. Explain how you were able to draw that conclusion. (4 marks)
Madhur L.
X-linked Disorders Traits carried on the sex (X or Y) chromosomes have a different inheritance pattern than those on the autosomal chromosomes. Although the X and Y chromosomes line up in meiosis I, they are not homologous and do not carry the same genes. For this reason, there is often only one allele present for a trait rather than two. X-linked disorders are carried on the X chromosome. Females have two copies of the X chromosomes, while males only have a single copy of the X chromosome. The cells of males only contain a single X chromosome; therefore, they cannot be considered homozygous or heterozygous for that allele. Instead, they are considered hemizygous, meaning that they only carry a single allele for that gene. For X-linked recessive disorders, because XY individuals are hemizygous, they are more commonly affected compared to XX individuals. X-linked Dominant For X-linked dominant traits, if the allele is present, it is expressed. Hypophosphatemic rickets is an X-linked dominant disease that causes rickets (weakening of the bone due to abnormal ossification). XR represents the Hypophosphatemic rickets allele. Xr represents the normal allele. Answer the following questions about a cross between a father who is Xr Y and a mother who is XR XR. What is the father's genotype (hemizygous dominant or hemizygous recessive)? What is the mother's genotype (heterozygous, homozygous dominant, or homozygous recessive)? What is the father's phenotype (affected or unaffected)? What is the mother's phenotype (affected, unaffected, carrier)? What are the potential gametes produced by the father? What are the potential gametes produced by the mother? Complete a Punnett square for a cross between these two individuals. Parent #1 -> Parent #2 -> What is the predicted ratio of phenotypes for the cross described? X-linked Recessive X-linked recessive traits are more likely to be expressed in males than in females. This is due to the hemizygous genotype. If only a single allele is present, and that allele is recessive, it will be expressed. In females, there are two alleles, and a dominant allele can mask the recessive allele. Hemophilia A affects approximately 1 in 4,000 males (NIH 2009). Hemophilia is caused by a lack of blood clotting factors. This can result in excessive bleeding that does not slow at a normal pace. XH represents the normal allele. Xh represents the hemophilia A allele. Answer the following questions about a cross between a father who is Xh Y and a mother who is XH Xh. What is the father's genotype (hemizygous dominant or hemizygous recessive)? What is the mother's genotype (heterozygous, homozygous dominant, or homozygous recessive)? What is the mother's phenotype (affected or unaffected)? What are the potential gametes produced by the father? What are the potential gametes produced by the mother? Complete a Punnett square for a cross between these two individuals. Parent #1 -> Parent #2 -> What is the predicted ratio of phenotypes for the cross described?
Katlin K.
In a pedigree of five generations of a family, at least one man in each generation displays symptoms of "condition alpha". None of the women are display symptoms of this genetic disorder. What is "condition alpha"? A sex-linked recessive trait. An autosomal recessive trait. A dominant trait. A co-dominant trait.
Mystique T.
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