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Ch. 4 - Gene Interaction
All textbooksSanders 3rd EditionCh. 4 - Gene InteractionProblem 6
Chapter 4, Problem 6

The ABO and MN blood groups are shown for four sets of parents (1 to 4) and four children (a to d). Recall that the ABO blood group has three alleles: IA, IB and i. The MN blood group has two codominant alleles, M and N. Using your knowledge of these genetic systems, match each child with every set of parents who might have conceived the child, and exclude any parental set that could not have conceived the child.
Table displaying ABO and MN blood groups for four parent sets and four children, illustrating genetic inheritance possibilities.
Table displaying ABO and MN blood groups for four children, with their respective blood types listed.

Verified step by step guidance
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Step 1: Determine the possible ABO genotypes of each set of parents based on their blood groups. Recall that the ABO blood group alleles are I^A, I^B, and i, where I^A and I^B are codominant and i is recessive. For example, a parent with blood group O must have genotype ii, blood group A could be I^AI^A or I^Ai, blood group B could be I^BI^B or I^Bi, and blood group AB must be I^AI^B.
Step 2: Determine the possible MN genotypes of each set of parents. Since M and N are codominant alleles, a parent with blood group M must be MM, with N must be NN, and with MN must be MN.
Step 3: For each child, analyze their ABO blood group and determine which parental genotypes could produce that blood group. Use Punnett squares or allele combinations to check if the child's ABO blood group is possible from the parents' genotypes. For example, a child with blood group AB must inherit I^A from one parent and I^B from the other.
Step 4: Similarly, analyze the MN blood group of each child and determine which parental MN genotypes could produce the child's MN blood group. Since M and N are codominant, a child with MN must inherit M from one parent and N from the other.
Step 5: Combine the ABO and MN results to match each child with the sets of parents who could have conceived them. Exclude any parental set where either the ABO or MN blood group inheritance is not possible based on the genotypes.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

ABO Blood Group Inheritance

The ABO blood group system is determined by three alleles: I^A, I^B, and i. I^A and I^B are codominant, meaning both can be expressed if present, while i is recessive. Blood types A, B, AB, and O result from different allele combinations, with O being homozygous recessive (ii). Understanding parental genotypes helps predict possible offspring blood types.
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MN Blood Group and Codominance

The MN blood group is controlled by two codominant alleles, M and N. Individuals with genotype MM express M antigen, NN express N antigen, and MN express both antigens. Since both alleles are equally expressed, offspring inherit one allele from each parent, allowing prediction of possible MN phenotypes.
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Genetic Compatibility and Exclusion

By comparing the blood groups of parents and children, one can determine if a parental pair could have conceived a child based on possible allele combinations. If a child's blood type cannot be derived from the parents' genotypes, that parental set is excluded. This principle is used in paternity testing and genetic counseling.
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Related Practice
Textbook Question

In a type of parakeet known as a "budgie," feather color is controlled by two genes. A yellow pigment is synthesized under the control of a dominant allele Y. Budgies that are homozygous for the recessive y allele do not synthesize yellow pigment. At an independently assorting gene, the dominant allele B directs synthesis of a blue pigment. Recessive homozygotes with the bb genotype do not produce blue pigment. Budgies that produce both yellow and blue pigments have green feathers; those that produce only yellow pigment or only blue pigment have yellow or blue feathers, respectively; and budgies that produce neither pigment are white (albino).

c. What are the genotype(s) and phenotype(s) of the F₁ progeny of the cross described in part (b)?

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Textbook Question

In a type of parakeet known as a "budgie," feather color is controlled by two genes. A yellow pigment is synthesized under the control of a dominant allele Y. Budgies that are homozygous for the recessive y allele do not synthesize yellow pigment. At an independently assorting gene, the dominant allele B directs synthesis of a blue pigment. Recessive homozygotes with the bb genotype do not produce blue pigment. Budgies that produce both yellow and blue pigments have green feathers; those that produce only yellow pigment or only blue pigment have yellow or blue feathers, respectively; and budgies that produce neither pigment are white (albino).

d. If F₁ males and females are mated, what phenotypes are expected in the F₂, and in what proportions?

615
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Textbook Question

In a type of parakeet known as a "budgie," feather color is controlled by two genes. A yellow pigment is synthesized under the control of a dominant allele Y. Budgies that are homozygous for the recessive y allele do not synthesize yellow pigment. At an independently assorting gene, the dominant allele B directs synthesis of a blue pigment. Recessive homozygotes with the bb genotype do not produce blue pigment. Budgies that produce both yellow and blue pigments have green feathers; those that produce only yellow pigment or only blue pigment have yellow or blue feathers, respectively; and budgies that produce neither pigment are white (albino).

e. The cross of a green budgie and a yellow budgie produces offspring that are 12 green, 4 blue, 13 yellow, and 3 albino. What are the genotypes of the parents?

646
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Textbook Question

The wild-type color of horned beetles is black, although other colors are known. A black horned beetle from a pure-breeding strain is crossed to a pure-breeding green female beetle. All of their F₁ progeny are black. These F₁ are allowed to mate at random with one another, and 320 F₂ beetles are produced. The F₂ consists of 179 black, 81 green, and 60 brown. Use these data to explain the genetics of horned beetle color.

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Textbook Question

Two genes interact to produce various phenotypic ratios among F₂ progeny of a dihybrid cross. Design a different pathway explaining each of the F₂ ratios below, using hypothetical genes R and T and assuming that the dominant allele at each locus catalyzes a different reaction or performs an action leading to pigment production. The recessive allele at each locus is null (loss-of-function). Begin each pathway with a colorless precursor that produces a white or albino phenotype if it is unmodified. The ratios are for F₂ progeny produced by crossing wild-type F₁ organisms with the genotype RrTt.

9/16 dark blue : 6/16 light blue : 1/16 white

329
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Textbook Question

Two genes interact to produce various phenotypic ratios among F₂ progeny of a dihybrid cross. Design a different pathway explaining each of the F₂ ratios below, using hypothetical genes R and T and assuming that the dominant allele at each locus catalyzes a different reaction or performs an action leading to pigment production. The recessive allele at each locus is null (loss-of-function). Begin each pathway with a colorless precursor that produces a white or albino phenotype if it is unmodified. The ratios are for F₂ progeny produced by crossing wild-type F₁ organisms with the genotype RrTt.

12/16 white : 3/16 green : 1/16 yellow

366
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