what are the chances that a particular child will have Huntington\'s disease? Au

Question

what are the chances that a particular child will have Huntington's disease?

Autosomal Dominant Disorder: Huntington's Disease . Huntington's disease is a neurological disease affecting humans. It has a late-onset and symptoms include involuntary muscle movements due to degeneration of the nervous system. Huntington's Disease is an autosomal dominant genetic disorder. A woman with the phenotype of Huntington's disease and the genotype Hh has children with a man with a normal (no Huntington's Disease) phenotype and the genotype hh. What are the chances that a particular child will have Huntington's Disease? a. Phenotypes of the parents Mother b. Genotypes of the parents Mother c. Gamete genotype(s) Father Father Sperm : - Egg d. Punnett Square (sperm) (egg) e. List all possible genotypes of offspring of these parents a. Which of these genotypes are heterozygous? b. Which of these genotypes are homozygous? f. List all the possible phenotypes of offspring of these parents g. Calculate the probability of each genotype and phenotype as listed. Fill in table below on the following page

Explanation / Answer

a) Huntigon disease is an autosomal dominant disease. Therefore the disease allele wil be represent by H and normal allele by h. Since it is a dominant disease one disease causing allele H is sufficient to cause the disease.

phenotype of mother : affected

phenotype of father : normal

genotype of mother : Hh

genotype of father : hh

Gametes of mother : H and h

Gametes of father: h

Possible genotype of offsprings of these parents : Hh and hh

Hh genotype is heterozygous as it contains one H mutant disease causing allele and one h normal allele.

hh genotype is homozygous as it contains both h alleles.

The possible phenotypes of offsprings of these parents is one affected with huntington disease and one normal offspring.

The chances that a child has huntington disease is 1/2 (in fraction) and 1/2 x 100 =50% (in percent). In punnet square see that offsprings with two different genotypes are possible Hh and hh. Hh will be affected and hh will be unaffected. Therefore out of 2 offsprings one is affected with huntington disease.

Gametes h H Hh (affected) h hh (normal)

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