Retinitis pigmentosa, a form of blindness in humans, may be caused by a dominant autosomal gene,...

Retinitis pigmentosa, a form of blindness in humans, may be caused by a dominant autosomal gene, R, or a recessive autosomal gene, a. Thus only A_ rr individuals have normal sight. An afflicted man whose parents are both normal marries a woman of genotype AaRr.

(A) What is the genotype of the afflicted man?

(B) What proportion of the children are expected to suffer from this affliction if R and A map to different chromosomes?

Expert Solution

Given that, there are two genes which control retinitis pigmentosa. It can be caused by dominant R allele, or recessive "a" allele.

This means only A_rr are unaffected, whereas aaR_ , A_R_ and aarr are affected.

The man is afflicted, and both of his parents were normal, A_rr. This means, the man will definitely inherit r allele from both parents, and thus it would be rr for the second gene. Thus, the only possible genotype of man is aarr. (Since affected ones cannot have dominant A allele, so the ma must be aa for the first gene).

The cross can be shown as :

(Man) aarr × AaRr (female)

Gamete from man : ar

Gametes from female : AR, Ar, aR and ar.

	ar
AR	AaRr (affected, due to R allele)
Ar	Aarr (normal)
aR	aaRr (affected, due to aa genotype)
ar	aarr (affected, due to aa genotype).

Thus, 3/4th children will be affected in this case.

Answer A: Genotype of man will be aarr.

Answer B: Proportion of children expected to suffer : 3/4 th or 75% or 0.75.

(kindly upvote if the answer was helpful).

gladiator answered 2 years ago

Genetic Inheritance Patterns: Retinitis pigmentosa (RP) can be autosomal recessive, autosomal dominant, or x-linked

Genetic Inheritance Patterns: Retinitis pigmentosa (RP) can be autosomal recessive, autosomal dominant, or x-linked. Apparently the dominant forms are often less severe. Usher’s Syndrome is an autosomal recessive inheritance (i.e., you must get a copy of the defective gene from your Mom and one from your Dad). Autosomal means it is not carried on one of the chromosomes that determines sex. One website (http://www.emedicine.com/oph/topic704.htm) says that Usher’s Syndrome Type II has been mapped to chromosome arm 1qe. Usher’s Type II...

In humans, hypercholesterolemia is a dominant autosomal disorder. Color-blindness is a recessive disorder carried on the...

In humans, hypercholesterolemia is a dominant autosomal disorder. Color-blindness is a recessive disorder carried on the X-chromosome. A woman with normal vision who does not have hypercholesterolemia takes her daughter to a doctor for an examination. In the course of the examination, the doctor discovers that the girl is color-blind and has hypercholesterolemia. What does the doctor automatically know about the genotype and phenotype of the girl’s father?

The human eye disease retinitis pigmentosa is caused by a loss of function mutation (rp) in...

The human eye disease retinitis pigmentosa is caused by a loss of function mutation (rp) in the gene PRPF31. The disease is expressed when combined with wildtype allele 1 (rp+1) in a heterozygote, but not expressed when combined with wildtype allele 2 (rp+2) in a heterozygote. When comparing the number PRPF31 mRNA transcripts in the eyes of rp/rp+1 and rp/rp+2 individuals, researchers have found a higher number of functional PRPF31 mRNAs in the eyes of rp/rp+2 individuals. This is an...

describe three autosomal dominant conditions in humans

Marfan syndrome (MFS) is an autosomal dominant hereditary disorder of connective tissue. It is caused by mutations in the glycoprotein gene, fibrillin-1 (FBN1).

7) Marfan syndrome (MFS) is an autosomal dominant hereditary disorder of connective tissue. It is caused by mutations in the glycoprotein gene, fibrillin-1 (FBN1). This syndrome can be described as a type of _______. a. epistasis b. haploinsufficiency c. aneuploidy d. trisomy --------------------------------------------- 8) Please refer to the following DNA sequence: 5’ GAGGCCTTAAATTT 3’ Which one of the changes listed below would be a structural chromosomal mutation to the sequence above? a. If first adenine is substituted with guanine....

Huntington's Disease is caused by an autosomal dominant allele. Suppose a prospective father is diagnosed with...

Huntington's Disease is caused by an autosomal dominant allele. Suppose a prospective father is diagnosed with this disease. His own mother also had it, but not his father. The prospective mother has no family history of the disease. a. What are the genotypes of these two prospective parents? (Tell how many copies of the dominant Huntington's allele the man and the woman each has.) b. What is the probability that a child of theirs would inherit the disease? Explain.

Red-green color blindness is caused by a mutation in a gene on the X chromosome. Xa...

Red-green color blindness is caused by a mutation in a gene on the X chromosome. Xa is the recessive mutant allele that causes color blindness; XA is the dominant, functional allele. You meet a patient who has Klinefelter syndrome (that is, he has an XXY karyotype). His mother is color blind, but his father has normal color vision. Your patient has both the XA and the Xa alleles. You hypothesize that your patient’s syndrome is due to a meiotic nondisjunction...

A certain type of congenital deafness in humans is caused by a rare dominant allele. In...

A certain type of congenital deafness in humans is caused by a rare dominant allele. In a mating involving a deaf man and a deaf woman, could all their children have normal hearing? a. Yes, because traits assort independently. b. No, because children favor their parents. c. No, because it is dominant. Children always get the dominant alleles. d. Yes, assuming that the parents are heterozygotes. e. Yes, because it must be recessive if it's rare.

Brachydactyly is a condition caused by an allele dominant to wild-type in humans, in which the...

Brachydactyly is a condition caused by an allele dominant to wild-type in humans, in which the fingers and toes are shortened. In a population of 10,000 people, 1,600 are BB, 4,800 are Bb, and 3,600 are bb. A)What percentage of people in this population have short fingers and toes? B)What is the frequency of the b allele? C)Is this population in Hardy-Weinberg equilibrium?

Another disease caused by a mutation in a single gene is Huntington’s disease (HD), an autosomal...

Another disease caused by a mutation in a single gene is Huntington’s disease (HD), an autosomal dominant condition. It is caused by mutations in a gene required for normal nerve cell function. The mutations cause abnormal proteins to be produced which “stick” together and accumulate in nerve cells, eventually interfering with normal cell operations. Suggest two ways you could treat the disease by targeting the translation step for the HD protein and justify why each approach might be effective.

Question