Textbook Question
Given the inheritance pattern of coat color in rats described in Problem 17, predict the genotype and phenotype of the parents who produced the following offspring:
9/16 gray: 3/16 yellow: 4/16 albino
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Ch. 4 - Modification of Mendelian Ratios
Klug10th EditionEssentials of GeneticsISBN: 9780135588789
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Table of contents
- Ch. 1 - Introduction to Genetics16
- Ch. 2 - Mitosis and Meiosis28
- Ch. 3 - Mendelian Genetics37
- Ch. 4 - Modification of Mendelian Ratios53
- Ch. 5 - Sex Determination and Sex Chromosomes32
- Ch. 6 - Chromosome Mutations: Variation in Number and Arrangement37
- Ch. 7 - Linkage and Chromosome Mapping in Eukaryotes36
- Ch. 8 - Genetic Analysis and Mapping in Bacteria and Bacteriophages24
- Ch. 9 - DNA Structure and Analysis38
- Ch. 10 - DNA Replication29
- Ch. 11 - Chromosome Structure and DNA Sequence Organization22
- Ch. 12 - The Genetic Code and Transcription36
- Ch. 13 - Translation and Proteins27
- Ch. 14 - Gene Mutation, DNA Repair, and Transposition34
- Ch. 15 - Regulation of Gene Expression in Bacteria22
- Ch. 16 - Regulation of Gene Expression in Eukaryotes37
- Ch. 17 - Recombinant DNA Technology27
- Ch. 18 - Genomics, Bioinformatics, and Proteomics30
- Ch. 19 - The Genetics of Cancer21
- Ch. 20 - Quantitative Genetics and Multifactorial Traits37
- Ch. 21 - Population and Evolutionary Genetics45
Chapter 4, Problem 11
In humans, the ABO blood type is under the control of autosomal multiple alleles. Color blindness is a recessive X-linked trait. If two parents who are both type A and have normal vision produce a son who is color-blind and is type O, what is the probability that their next child will be a female who has normal vision and is type O?
Verified step by step guidance1
Determine the genotypes of the parents for the ABO blood group. Since both parents are type A but have a child with type O, each parent must be heterozygous with genotype \(I^A i\) (where \(I^A\) is the allele for type A and \(i\) is the allele for type O).
Analyze the inheritance of the ABO blood group for the next child. Use a Punnett square to find the probability that the child will inherit the \(i\) allele from both parents, resulting in blood type O (\(ii\) genotype).
Determine the genotypes of the parents for the X-linked color blindness trait. Both parents have normal vision, but they have a color-blind son. Since color blindness is recessive and X-linked, the mother must be a carrier with genotype \(X^N X^c\) (where \(X^N\) is the normal allele and \(X^c\) is the color-blind allele), and the father must have normal vision with genotype \(X^N Y\).
Calculate the probability that the next child will be female and have normal vision. The child must inherit an \(X^N\) from the mother and an \(X^N\) from the father to have normal vision and be female (\(X^N X^N\)).
Combine the probabilities from the ABO blood group and the X-linked trait, and multiply by the probability that the child is female (which is 1/2), to find the overall probability that the next child will be a female with normal vision and blood type O.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Multiple Alleles and ABO Blood Group Inheritance
The ABO blood group is determined by three alleles (IA, IB, and i) located on an autosome. IA and IB are codominant, while i is recessive. Blood type A can be genotype IAIA or IAi, and blood type O is ii. Understanding these allele interactions is essential to predict offspring blood types.
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02:45
Haploid Genetics
X-linked Recessive Inheritance and Color Blindness
Color blindness is caused by a recessive allele on the X chromosome. Males (XY) express the trait if they inherit the affected X, while females (XX) must inherit two copies to be affected. Carrier females have one normal and one affected allele and show normal vision but can pass the trait to offspring.
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00:52Purpose of X Inactivation
Probability Calculation in Genetic Crosses
Calculating the probability of offspring traits involves combining independent probabilities of genotype and sex. This requires determining parental genotypes, using Punnett squares for autosomal and sex-linked traits, and multiplying probabilities for combined traits like blood type, vision, and sex.
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07:41Probability
Related Practice
Textbook Question
Given the inheritance pattern of coat color in rats described in Problem 17, predict the genotype and phenotype of the parents who produced the following offspring: 27/64 gray:
16/64 albino: 9/64 yellow: 9/64 black: 3/64 cream
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Textbook Question
A husband and wife have normal vision, although both of their fathers are red–green color-blind, an inherited 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 son, (d) a color-blind daughter?
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Textbook Question
In goats, the development of the beard is due to a recessive gene. The following cross involving true-breeding goats was made and carried to the F₂ generation:
Offer an explanation for the inheritance and expression of this trait, diagramming the cross. Propose one or more crosses to test your hypothesis.
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