Huntigtons disease is a genetic disorder caused by a dominant lethal allele. The condition is a progressive breakdown of nerve cells that causes uncontrolled movement. The disorder can be found on the dominant H allele (which is rare ..... because usually disorders are recessive!). If the father is homozygous dominant for the trait and the mother does not have the trait, what is the phenotypic probability for their children?

MONOHYBRID CROSS

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Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]

Huntigton’s disease is a genetic disorder caused by a dominant lethal allele. The condition is a progressive breakdown of nerve cells that causes uncontrolled movement. The disorder can be found on the dominant H allele (which is rare ____ because usually disorders are recessive!). If the father is homozygous dominant for the trait and the mother does not have the trait, what is the phenotypic probability for their children?

A	1 HH:1 Hh
B	1 Hh:1 hh
C	1 HH:2 Hh:1 hh
D	1 Have Huntington’s:1 Does not have Huntington’s
E	1 Have Huntington’s

Explanation:

Detailed explanation-1: -Huntington’s disease is an autosomal dominant disorder, which means that a person needs only one copy of the nontypical gene to develop the disorder. With the exception of genes on the sex chromosomes, a person inherits two copies of every gene-one copy from each parent.

Detailed explanation-2: -HD is caused by a mutation in the gene for a protein called huntingtin. The defect causes the building blocks of DNA called cytosine, adenine, and guanine (CAG) to repeat many more times than they normally do. Most people have fewer than 27 CAG repeats in their HD gene, so they are not at risk for the disease.

Detailed explanation-3: -No treatments can alter the course of Huntington’s disease. But medications can lessen some symptoms of movement and psychiatric disorders. And multiple interventions can help a person adapt to changes in abilities for a certain amount of time.

There is 1 question to complete.

AP BIOLOGY

HEREDITY

MONOHYBRID CROSS