The genotype of F1 individuals in tetrahybrid cross is AaBbCcDd. Assuming independent assortment of these four genes, what are the probabilities that F2 offspring will have the following genotypes?

(a) aabbccdd

(b) AaBbCcDd

(c) AABBCCDD

(d) AaBBccDd

(e) AaBBCCdd

Short Answer

Expert verified

(a) The probability of F2 offspring with the genotype aabbccdd is 1/256.

(b) The probability of F2 offspring with the genotype AaBbCcDd is 1/16.

(c) The probability of F2 offspring with the genotype AABBCCDD is 1/256.

(d) The probability of F2 offspring with the genotype AaBBccDd is 1/64.

(e) The probability of F2 offspring with the genotype AaBBCCdd is 1/128.

Step by step solution

01

Pattern of inheritance and probability of inheritance of traits

Inheritance is the transfer of genes from the parents to the offspring. The inheritance occurs via sexual reproduction, and the offspring generated from the parents are known as F1 offspring.

F2 offspring are obtained by crossing the F1 hybrid.

In general, the probability of occurrence of a homozygous trait “XX or xx” is ¼, and the probability of occurrence of a heterozygous trait “Xx” is ½.

02

Explanation of part “a”

The given offspring is aabbccdd. All the traits are homozygous for the four recessive traits. Thus, the probability of the F2 offspring is as follows:

Probability=14×14×14×14=1256

03

Explanation of part “b”

The given F2 offspring is AaBbCcDd. All the given traits are heterozygous for each trait. Thus, the probability of the F2 offspring is as follows:

Probability=12×12×12×12=116

04

Explanation of part “c”

F2 offspring given in the question is AABBCCDD. The genotypic combination provided is homozygous for four dominant traits. Thus, the probability of the F2 offspring is as follows:

Probability=14×14×14×14=1256

05

Explanation of part “d”

F2 offspring given in the question is AaBBccDd. Aa and Dd are heterozygous for the traits, so they have a probability of ½ each. BB and cc are homozygous for dominant and recessive traits, respectively, so they have a probability of ¼ each.

Thus, the overall probability of the F2 offspring is as follows:

Probability=12×12×14×14=164

06

Explanation of part “e”

F2given in the question isAaBBCCdd. In this genotype, Aa is heterozygous for a trait with a probability is 1/2. BB, CC, and dd are homozygous for the traits, each with the probability of ¼.

Thus, the overall probability of the F2 offspring is as follows:

Probability=12×14×14×14=1128

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Most popular questions from this chapter

You are handed a mystery pea plant with tall stems and axial flowers and asked to determine its genotype as quickly as possible. You know that the allele for tall stems (T) is dominant to that for dwarf stems (t) and that the allele for axial flowers (A) is dominant to that for terminal flowers (a).

(a) Identify all the possible genotypes for your mystery plant.

(b) Describe the one cross you would do, out in your garden, to determine the exact genotype of your mystery plant.

(c) While waiting for the results of your cross, you predict the results for each possible genotype listed in part a. Explain how you do this and why this is not called “performing a cross.”

(d) Explain how the results of your cross and your predictions will help you learn the genotype of your mystery plant.

Two organisms, with genotypes BbDDand BBDd, are mated. Assuming independent assortment of the B/band D/dgenes, write the genotypes of all possible offspring from this cross and use the rules of probability to calculate the chance of each genotype occurring.

A man has six fingers on each hand and six toes on each foot. His wife and their daughter have the normal number of digits. Remember that extra digits are a dominant trait. What fraction of this couple's children would be expected to have extra digits?

Imagine that you are a genetic counselor, and a couple planning to start a family comes to you for information. Charles was married once before, and he and his first wife had a child with cystic fibrosis. The brother of his current wife, Elaine, died of cystic fibrosis. What is the probability that Charles and Elaine will have a baby with cystic fibrosis? (Neither Charles, Elaine, nor their parents have cystic fibrosis.)

Two pea plants heterozygous for the characters of pod color and pod shape are crossed. Draw a Punnet square to determine the phenotypic ratios of the offspring.

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