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Ch. 4 - Modification of Mendelian Ratios
Klug - Essentials of Genetics 10th Edition
Klug10th EditionEssentials of GeneticsISBN: 9780135588789Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoKlug 10th EditionCh. 4 - Modification of Mendelian RatiosProblema 21b
Capitolo 4, Problema 21b

Consider the three pedigrees below, all involving a single human trait.

For each combination that you excluded, indicate the single individual in generation II (e.g., II-1, II-2) that was most instrumental in your decision to exclude it. If none were excluded, answer 'none apply.'

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Step 1: Identify the trait pattern in each pedigree by noting which individuals are affected (shaded) and which are unaffected (unshaded). This helps determine if the trait is dominant or recessive.
Step 2: For each pedigree, analyze the inheritance pattern by considering the genotypes of the parents (generation I) and their offspring (generation II). Use the rules of Mendelian inheritance to predict possible genotypes.
Step 3: Check for inconsistencies in each pedigree. For example, if the trait is dominant, an affected individual must have at least one affected parent. If this is not the case, exclude that inheritance pattern and identify the individual in generation II who contradicts it.
Step 4: For recessive traits, ensure that affected individuals have parents who are either carriers or affected. If an affected individual has two unaffected parents who cannot be carriers, exclude that pattern and identify the key individual in generation II.
Step 5: Summarize your exclusions by listing the specific individual in generation II from each pedigree that led to the exclusion of a particular inheritance pattern. If no contradictions are found, state 'none apply.'

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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 determine whether a trait is dominant, recessive, autosomal, or sex-linked. Understanding how to interpret these symbols and relationships is essential for analyzing genetic inheritance.
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Pedigree Flowchart

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. Each mode has distinct characteristics, such as affected individuals appearing in every generation for dominant traits or skipping generations for recessive traits, which are critical for excluding or confirming possible inheritance patterns in pedigrees.
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Organelle Inheritance

Genotype-Phenotype Correlation in Pedigrees

Genotype-phenotype correlation involves linking the observed traits (phenotypes) in a pedigree to the underlying genetic makeup (genotypes). Identifying which individuals must carry or lack certain alleles based on their phenotype helps exclude incompatible inheritance patterns. This concept is key to pinpointing individuals in generation II who are instrumental in ruling out specific genetic models.
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Autosomal Pedigrees
Pratica correlata
Domanda del libro di testo

Consider the three pedigrees below, all involving a single human trait.

Which combination of conditions, if any, can be excluded? dominant and X-linked dominant and autosomal recessive and X-linked recessive and autosomal

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Domanda del libro di testo

Consider the three pedigrees below, all involving a single human trait.

Given your conclusions in part (a), indicate the genotype of the following individuals: II-1, II-6, II-9 If more than one possibility applies, list all possibilities. Use the symbols A and a for the genotypes.

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Domanda del libro di testo

Labrador retrievers may be black, brown (chocolate), or golden (yellow) in color (see chapter-opening photo). While each color may breed true, many different outcomes are seen when numerous litters are examined from a variety of matings where the parents are not necessarily true breeding. Following are just some of the many possibilities.

(a) black x brown → all black

(b) black x brown → 1/2 black, 1/2 brown

(c) black x brown → 3/4 black, 1/4 golden

(d) black x golden → all black

(e) black x golden → 4/8 golden 3/8 black 1/8 brown

(f) black x golden → 2/4 golden 1/4 black 1/4 brown

(g) brown x brown → 3/4 brown 1/4 golden

(h) black x black → 9/16 black 4/16 golden, 3/16 brown

Propose a mode of inheritance that is consistent with these data, and indicate the corresponding genotypes of the parents in each mating. Indicate as well the genotypes of dogs that breed true for each color.

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