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Chapter 4: Problem 10

A husband and wife have normal vision, although both of their fathers are red- green color-blind, inherited as an X-linked recessive condition. What is the probability that their first child will be (a) a normal son, (b) a normal daughter, (c) a color-blind \(\operatorname{son},(d)\) a color-blind daughter?

Short Answer

Expert verified
Answer: The probabilities are as follows: (a) normal son: 1/4, (b) normal daughter: 1/4, (c) color-blind son: 1/4, and (d) color-blind daughter: 0.

Step by step solution

01

Understanding the given information

Since both husbands and wives have normal vision, it means they are both carriers of the colorblind gene (Xc) inherited from their fathers, who were colorblind. Their genotypes are XcX for the wife and XcY for the husband.
02

Creating the Punnett Square

We will create a Punnett square for the possible genotypes of their children. In the rows, we will place the wife's alleles (Xc and X) and in the columns, we will place the husband's alleles (Xc and Y): Xc Y -------------- Xc | XcXc | XcY -------------- X | XX | XY
03

Identifying the outcomes

We can now identify the possible outcomes for their children based on the Punnett square: - XcXc (color-blind daughter) - XX (normal daughter) - XcY (color-blind son) - XY (normal son)
04

Calculating the probabilities

To find the probability of each outcome, we will calculate the ratio of the desired outcome among the four possibilities. (a) The probability of having a normal son (XY) is 1/4 (b) The probability of having a normal daughter (XX) is 1/4 (c) The probability of having a color-blind son (XcY) is 1/4 (d) The probability of having a color-blind daughter (XcXc) is 0/4 or 0, as it's not possible for them to have a color-blind daughter since the mother has a normal X chromosome. In conclusion, the husband and wife have probabilities of having: (a) a normal son: 1/4 (b) a normal daughter: 1/4 (c) a color-blind son: 1/4 (d) a color-blind daughter: 0

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Most popular questions from this chapter

The specification of the anterior-posterior axis in Drosophila embryos is initially controlled by various gene products that are synthesized and stored in the mature egg following oogenesis. Mutations in these genes result in abnormalities of the axis during embryogenesis, illustrating maternal effect. How do such mutations vary from those involved in organelle heredity that illustrate extranuclear inheritance? Devise a set of parallel crosses and expected outcomes involving mutant genes that contrast maternal effect and organelle heredity.

The maternal-effect mutation bicoid (bcd) is recessive. In the absence of the bicoid protein product, embryogenesis is not completed. Consider a cross between a female heterozygous for the bicoid mutation \(\left(b c d^{+} / b c d^{-}\right)\) and a homozygous male \(\left(b c d^{\left.-/ b c d^{-}\right)}\right.\) (a) How is it possible for a male homozygous for the mutation to exist? (b) Predict the outcome (normal vs, failed embryogenesis) in the \(\mathrm{F}_{1}\) and \(\mathrm{F}_{2}\) generations of the cross described.

Pigment in the mouse is produced only when the \(C\) allele is pres- ent. Individuals of the ce genotype have no color, If color is present, it may be determined by the \(A\) and \(a\) alleles. AA or Aa results in agouti color, whereas aa results in black coats. (a) What \(\mathrm{F}_{1}\) and \(\mathrm{F}_{2}\) genotypic and phenotypic ratios are obtained from a cross between \(A A C C\) and aace mice? (b) In the three crosses shown here between agouti females whose genotypes were unknown and males of the aacc genotype, what are the genotypes of the female parents for each of the following phenotypic ratios? (1) 8 agouti (2) 9 agouti (3) 4 agouti 8 colorless 10 black \(\quad 5\) black 10 colorless

What genetic criteria distinguish a case of extranuclear inheritance from (a) a case of Mendelian autosomal inheritance; (b) a case of \(\mathrm{X}\) -linked inheritance?

A geneticist from an alien planet that prohibits genetic research brought with him two true-breeding lines of frogs. One frog line croaks by uttering "rib-it rib-it" and has purple eyes. The other frog line croaks by muttering "knee- deep knee-deep" and has green eyes. He mated the two frog lines, producing \(\mathrm{P}_{1}\) frogs that were all utterers with blue eyes. A large \(\mathrm{F}_{2}\) generation then yielded the following ratios: \(27 / 64\) blue, utterer \(12 / 64\) green, utterer \(9 / 64\) blue, mutterer \(9 / 64\) purple, utterer \(4 / 64\) green, mutterer \(3 / 64\) purple, mutterer (a) How many total gene pairs are involved in the inheritance of both eye color and croaking? (b) Of these, how many control eye color, and how many control croaking? (c) Assign gene symbols for all phenotypes, and indicate the genotypes of the \(P_{1}, F_{1},\) and \(F_{2}\) frogs. (d) After many years, the frog geneticist isolated true-breeding lines of all six \(\mathrm{F}_{2}\) phenotypes. Indicate the \(\mathrm{F}_{1}\) and \(\mathrm{P}_{2}\) phenotypic ratios of a cross between a blue, mutterer and a purple, utterer.
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