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: 3/16 black: 1/16 cream
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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 10
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?
Verified step by step guidance1
Identify the inheritance pattern: Red-green color blindness is an X-linked recessive trait. This means the gene causing the condition is located on the X chromosome, and the trait manifests in males who have only one X chromosome carrying the mutation, or in females who have two mutated X chromosomes.
Determine the genotypes of the parents: Both husband and wife have normal vision, but both of their fathers are color-blind. Since fathers pass their X chromosome to their daughters, the wife must be a carrier (X\^N X\^c), where X\^N is the normal allele and X\^c is the color-blind allele. The husband has normal vision and a color-blind father, so he must have inherited his Y chromosome from his father and a normal X chromosome from his mother (X\^N Y).
Set up the possible gametes: The wife can produce eggs with either X\^N or X\^c, each with a probability of 1/2. The husband can produce sperm with either X\^N or Y, each with a probability of 1/2.
Construct a Punnett square to combine the gametes and determine the genotypes of the children: The four possible combinations are X\^N X\^N (normal daughter), X\^c X\^N (carrier daughter), X\^N Y (normal son), and X\^c Y (color-blind son).
Calculate the probabilities for each child type: (a) normal son corresponds to X\^N Y, (b) normal daughter corresponds to X\^N X\^N, (c) color-blind son corresponds to X\^c Y, and (d) color-blind daughter corresponds to X\^c X\^c (which is not possible here since the mother is a carrier, not affected). Use the Punnett square ratios to find each probability.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
X-linked Recessive Inheritance
X-linked recessive traits are caused by mutations on the X chromosome. Males (XY) express the trait if they inherit the affected X, while females (XX) must inherit two affected X chromosomes to express the trait. Females with one affected X are carriers and usually phenotypically normal.
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09:30
X-Inactivation
Carrier Status and Phenotype in X-linked Traits
A female carrier has one normal and one mutated X chromosome, typically showing no symptoms but able to pass the mutation to offspring. Sons of carrier mothers have a 50% chance of being affected, while daughters have a 50% chance of being carriers.
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09:30X-Inactivation
Probability Calculation in Genetic Crosses
Genetic probabilities are calculated by considering parental genotypes and possible gametes. For X-linked traits, the sex of the child affects inheritance patterns, so probabilities differ for sons and daughters based on the mother’s carrier status and father’s genotype.
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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:
9/16 gray: 3/16 yellow: 4/16 albino
559
views
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
457
views
Textbook Question
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?
1181
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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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