Questions and Answers
Which inheritance pattern is characterized by the presence of a recessive trait requiring two copies of the recessive allele for phenotype expression?
What type of allelic interaction occurs when both alleles in a heterozygote are expressed equally, resulting in a phenotype that is a blend of both traits?
Which inheritance pattern would most likely affect males more than females, as it is located on the X chromosome and is inherited in a recessive manner?
Which of the following best describes a scenario where three or more alleles exist for a single trait within a population?
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In which type of inheritance pattern would a daughter inherit the trait from either one of her parents, but sons would inherit it only from their mother?
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Study Notes
Inheritance Patterns of Traits
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Autosomal Recessive:
- Trait expressed only when an individual has two copies of the recessive allele.
- Individuals with one dominant allele are carriers and display no symptoms.
- Examples include cystic fibrosis and sickle cell anemia.
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Autosomal Dominant:
- Trait expressed with just one copy of the dominant allele.
- Affected individuals can pass the trait to offspring with a 50% chance.
- Examples include Huntington’s disease and Marfan syndrome.
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X-Linked Recessive:
- Trait linked to genes on the X chromosome; predominantly affects males.
- Males with one affected X will express the trait, while females need two affected X chromosomes.
- Common conditions include hemophilia and Duchenne muscular dystrophy.
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X-Linked Dominant:
- Trait expressed in individuals with one copy of the dominant allele on the X chromosome.
- Both males and females can be affected, but males may exhibit more severe symptoms.
- Conditions include Rett syndrome and X-linked hypophosphatemia.
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Y-Linked:
- Traits associated with genes on the Y chromosome, affecting only males.
- Passed from father to son with a 100% inheritance rate.
- Examples include certain forms of male infertility and Y chromosome microdeletions.
Allelic Interactions
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Incomplete Dominance:
- Heterozygous phenotype is a blend of both alleles, clearly different from both homozygous phenotypes.
- Example: In snapdragons, crossing red and white flowers results in pink flowers.
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Codominance:
- Both alleles are fully expressed in the phenotype of heterozygotes.
- Example: Blood type AB expresses both A and B antigens.
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Multiple Allelism:
- More than two alleles exist for a single gene within a population, though an individual can only possess two alleles.
- Example: ABO blood group system has three alleles (I^A, I^B, i) with combinations determining blood type.
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Description
Test your understanding of inheritance patterns such as autosomal recessive, autosomal dominant, and sex-linked traits. Explore concepts of allelic interaction, including incomplete dominance, codominance, and multiple allelism. This quiz covers essential genetic principles and mechanisms.
