Questions and Answers
Which symbol is used to label a male that expresses a sex-linked disorder on a pedigree?
Based on the pedigree that is shown, John has hemophilia.
False
Fathers always determine the gender of the offspring in humans.
True
What is the purpose of using a pedigree?
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How are the alleles for sex-linked traits inherited?
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What was Thomas Hunt Morgan's main contribution to science?
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What is the probability of the offspring having hemophilia for the given cross?
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A patient who is Rh- can receive only Rh- blood.
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Which Punnett square shows a cross in which the probability of offspring having red eyes is 100 percent?
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What is the probability that a female offspring would have a recessive allele for Duchenne muscular dystrophy disorder?
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What is the genotype for a recessive trait found on the female chromosome?
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Which allele combination represents a female who is a carrier for an X-linked recessive disorder?
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The alleles for sex-linked inheritance are found on either the X or Y chromosome.
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Which allele combination represents a female who is heterozygous for a sex-linked trait?
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Which pedigree symbol is used to represent a female carrier of a recessive X-linked trait?
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What is the probability that a female child of Charles and Marie would suffer from hemophilia?
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Which combination of alleles are always involved in the inheritance of a sex-linked trait?
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Study Notes
Sex-Linked Inheritance Key Concepts
- Male Symbol in Pedigree: Represented by a purple square (D) for individuals expressing a sex-linked disorder.
- Hemophilia in Pedigrees: An X-linked recessive disorder (Xh); John does not have hemophilia according to the analyzed pedigree.
- Gender Determination: In human offspring, fathers determine the gender.
- Purpose of Pedigree: Used to trace and understand the inheritance patterns of traits in organisms.
- Inheritance of Sex-Linked Traits: Passed from parents to offspring via the X and Y chromosomes.
Historical Insights
- Thomas Hunt Morgan's Contribution: Discovered the link between certain traits and the X chromosome.
Probability and Genetics
- Probability of Hemophilia: For specific crosses shown in a Punnett square, there is a 50 percent chance of offspring inheriting hemophilia.
- Duchenne Muscular Dystrophy: Affected female offspring from a given cross will definitely inherit the recessive allele (100 percent probability).
Genotype and Carrier Status
- Genotype for Recessive Trait in Females: Denoted as Xh.
- Allele Combination for Female Carriers: Represented as XRXr, indicating one normal and one recessive allele.
- Heterozygous Females: Also represented by XRXr for sex-linked traits.
Pedigree Symbols
- Carrier Symbol for Females: A half-filled circle (B) indicates a carrier of a recessive X-linked trait.
- Probability of Female Children with Hemophilia: In certain crosses, there is a 0 percent chance of a female child having hemophilia.
General Principles
- Allele Involvement in Sex-Linked Traits: Traits are inherited through alleles located on X and Y chromosomes.
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Description
Test your understanding of sex-linked inheritance through key concepts and examples. This quiz covers topics such as pedigree analysis and X-linked disorders like hemophilia. Challenge yourself with questions that reinforce your knowledge of genetic inheritance patterns.
