Problem The only member of Arlenes family who is color blind is her brotber. Wha

Question

Problem The only member of Arlenes family who is color blind is her brotber. What is her brother's genotype her father's genotype?her mother's gcnosype?What is Arlene's genotype if she later has a color-blind son? Ability to Taste PTC PTC (phenylthiocarbamide) is an antithyroid drug that prevents the thyroid gland from incorporating iodine isto the thyroid hormone. The ability to taste PTC is associated with the functioning o s the thyroid gland. As with many patter of human iaheritance, the nature of the relationship between "tasting" and disease is unknown. The ability to taste PTC is an autosomal trait. Tasting (T) is dominant to nontasting (o) Your Genotype Taste a piece of paper impregnated with PTC. Can you taste this chemical?o, what is your genotype? If you are able to taste the chemical, then you must sest your parents and any other childrem in your family in arder to determine your complete genotype. Obrain suficient strips of PTC paper to test your parents and sibliags. Do not warn those you test of the possible results, since this may make them think they taste something. If you are not liwing with your family, choose another family to test TSC Can your father taste the chemical? Can your mother taste the chemical, Can your brothers and sisters taste the chemical? What is your complete genotype? How do you know? Problem Joe cannot taste PTC, but both his mother and father can taste PTC. Do a Punnett square to calculate the expectod phenotypic ratio among the offspring. Ratio Square What are the chances that a child in this family will be able to taste PTC?will not be able? 20-3

Explanation / Answer

1.The only member of Arlene’s family who is coloblind is her brother.

C-Normal gene

c-colorblind gene

Brother's genotype :XcY

father's genotype:XCY

Mother's genotype:XCXc

Arlene's genotype:XCXc

Explanation: Color blindness is a X linked recessive trait.In males, a single recessive gene present on X chromosome expresses the trait while in females presence of two recessive genes on 2X chromosomes are required to express tha trait.Females can be normal but carriers when they possess one copy of the normal dominant gene and other copy of the recessive gene.Females pass their recessive colorblind gene on X chromosome to sons and they are affected.Affected sons will have either carrier mother or affected mother.Affected daughters will have either carrier /affected mother and affected father.

2.This is to be done by self family activity.

3.Since Joe cannot taste PTC,it means that he is recessive(tt) for the trait.

Tasting(T) is dominant to no tasting (t)

As Joe cannot taste PTC and hence is recessive and his parents can taste PTC, it means they will be either TT or Tt.But Joe is recessive and he must have received one recessive allele from each parent.

Punnet square will be:

father

Genotype ratio: TT:Tt:tt = 1:2:1

phenotype ratio: tasting:non tasting = 3:1

Chances that a child will be able to taste PTC = 3/4 = 0.75

Chances that a child will not be able to taste PTC =1/4 =0.25

mother T t T TT tasting Tt tasting t Tt tasting tt non tasting

Related Questions

Navigate

• Browse (All)
• Browse P
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.