Ch. 3 - Mendelian Genetics

Klug - Concepts of Genetics 12th Edition

Klug12th EditionConcepts of Genetics ISBN: 9780135564776Not the one you use?Change textbook

Klug 12th Edition

Ch. 3 - Mendelian Genetics

Problem 22b

Chapter 3, Problem 22b

Draw all possible conclusions concerning the mode of inheritance of the trait portrayed in the following limited pedigree.

Verified step by step guidance

Step 1: Identify the affected and unaffected individuals in the pedigree. The filled square represents an affected male, while all other symbols (open squares and circles) represent unaffected individuals.

Step 2: Determine the generation and family relationships. The pedigree shows two generations: the first generation consists of unaffected parents, and the second generation includes their children, among whom one male is affected.

Step 3: Consider the mode of inheritance possibilities. Since only one male is affected and the parents are unaffected, consider whether the trait could be autosomal dominant, autosomal recessive, X-linked dominant, or X-linked recessive.

Step 4: Analyze the likelihood of each mode: - Autosomal dominant traits usually appear in every generation, so an affected child with unaffected parents is less likely. - Autosomal recessive traits can appear in offspring of unaffected parents if both are carriers. - X-linked recessive traits often affect males more frequently and can be passed from carrier mothers to sons. - X-linked dominant traits usually affect both males and females and often have affected mothers.

Step 5: Conclude that the trait is most consistent with an X-linked recessive inheritance pattern because only one male is affected, the parents are unaffected, and the trait appears only in a male child, which fits the pattern of X-linked recessive traits.

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Key Concepts

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

Pedigree Analysis

Pedigree analysis is a tool used to study the inheritance patterns of traits through generations in a family. It uses standardized symbols to represent individuals and their traits, helping to identify whether a trait is dominant, recessive, autosomal, or sex-linked.

Modes of Inheritance

Modes of inheritance describe how traits are passed from parents to offspring, including autosomal dominant, autosomal recessive, X-linked dominant, and X-linked recessive patterns. Recognizing these patterns in pedigrees helps determine the genetic basis of a trait.

Interpretation of Affected and Unaffected Individuals

In pedigrees, affected individuals are typically shaded, while unaffected are unshaded. Analyzing the distribution of affected individuals across generations and sexes provides clues about the trait's inheritance, such as whether it skips generations or affects one sex more frequently.

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Textbook Question

For decades scientists have been perplexed by different circumstances surrounding families with rare, early-onset auditory neuropathy (deafness). In some families, parents and grandparents of the proband have normal hearing, while in other families, a number of affected (deaf) family members are scattered throughout the pedigree, appearing in every generation. Assuming a genetic cause for each case, offer a reasonable explanation for the genetic origin of such deafness in the two types of families.

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Textbook Question

Draw all possible conclusions concerning the mode of inheritance of the trait portrayed in the following limited pedigree.

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Textbook Question

Draw all possible conclusions concerning the mode of inheritance of the trait portrayed in the following limited pedigree.

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Textbook Question

The basis for rejecting any null hypothesis is arbitrary. The researcher can set more or less stringent standards by deciding to raise or lower the p value used to reject or not reject the hypothesis. In the case of the chi-square analysis of genetic crosses, would the use of a standard of p = 0.10 be more or less stringent about not rejecting the null hypothesis? Explain.

Textbook Question

Draw all possible conclusions concerning the mode of inheritance of the trait portrayed in the following limited pedigree.

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Textbook Question

Consider the following pedigree.

Predict the mode of inheritance of the trait of interest and the most probable genotype of each individual. Assume that the alleles A and a control the expression.

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