Questions and Answers
Which of the following traits is classified as Y-linked?
What is a characteristic of Y-linked inheritance?
What condition is described as the thickening and darkening of the skin with bristle-like outgrowths?
What defines a sex-limited trait?
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What must be true for a recessive allele on the X chromosome to be expressed in females?
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Which of the following is a sex-influenced trait?
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Which of these conditions does NOT skip generations?
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Why are sex-linked disorders often more prevalent in males than females?
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What characteristic is typical of sex-influenced traits?
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Which trait is influenced by genetic factors present on autosomes but expressed differently based on sex?
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Which of the following traits is NOT an example of an X-linked recessive trait?
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What would render a pedigree to not be classified as X-linked recessive inheritance?
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What describes a characteristic of X-linked dominant inheritance?
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Which sex-linked trait is classified as recessive?
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How can the probability of a child inheriting a sex-linked trait be calculated?
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Study Notes
Sex-Linked Inheritance Overview
- Sex-linked traits are determined by genes located on the sex chromosomes (X or Y).
- X-linked traits have the gene on the X chromosome, while Y-linked traits have the gene on the Y chromosome.
X-Linked Recessive Traits
- Disorders like hemophilia and color blindness are examples of X-linked recessive traits.
- Females require two copies of the recessive allele (one on each X chromosome) to express the trait. Males, having one X, express the trait with just one recessive allele.
Hemophilia Example
- In a cross between a woman with hemophilia (XhXh) and a normal man (XHY):
- Punnett square can be used to calculate probabilities for offspring.
- Sons have a probability of 100% being hemophiliac.
- Daughters have a 0% probability of being hemophiliac.
Inheritance Patterns
- X-linked dominant inheritance affects both sons and daughters if the mother is affected.
- X-linked recessive inheritance often presents differently in pedigree analysis, where affected males directly influence the likelihood of affected sons.
Y-Linked Inheritance
- Traits linked to the Y chromosome affect only males and do not skip generations.
- Hypertrichosis pinnae auris is a Y-linked trait where affected males show hair growth from their external ears.
Other Y-Linked Traits
- Conditions such as Porcupine man (skin condition) and webbed toes (connection between toes) are examples of Y-linked traits.
Sex-Influenced and Sex-Limited Traits
- Sex-Influenced Traits: Traits controlled by genes on autosomes with expression influenced by the individual's sex, such as baldness.
- Sex-Limited Traits: Traits expressed only in one biological sex, like breast development in females and beard growth in males.
Assignment Guidelines
- Infographic/poster project about a sex-linked trait or disorder (excluding hemophilia).
- Emphasis on content accuracy, organization, creativity, and mechanics with a total grading scale of 100%.
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Description
This quiz covers the fundamentals of sex-linked inheritance, focusing on X-linked and Y-linked traits. It highlights specific disorders such as hemophilia and color blindness, detailing their inheritance patterns and implications for offspring probabilities. Understand key concepts with the use of Punnett squares and explore different inheritance scenarios.
