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Questions and Answers
What determines whether an allele is classified as dominant or recessive?
What determines whether an allele is classified as dominant or recessive?
In the case of codominance, what occurs between the alleles?
In the case of codominance, what occurs between the alleles?
Why is hemophilia more common in males than in females?
Why is hemophilia more common in males than in females?
What is the phenotype of a person with the genotype XH Xh?
What is the phenotype of a person with the genotype XH Xh?
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How many copies of a recessive allele are required to show its effect in an individual?
How many copies of a recessive allele are required to show its effect in an individual?
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What happens if both alleles in an individual are dominant?
What happens if both alleles in an individual are dominant?
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What are the two versions of a gene referred to as?
What are the two versions of a gene referred to as?
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If a male inherits an X chromosome with a hemophilia allele, what can be concluded?
If a male inherits an X chromosome with a hemophilia allele, what can be concluded?
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Study Notes
Dominant and Recessive Alleles
- Different versions of a gene are called alleles. Alleles can be dominant or recessive, affecting traits.
- Humans have two versions of each gene, inherited from each parent.
- Dominant alleles express their effect even if only one copy is present (heterozygous).
- Recessive alleles only express their effect when two copies are present (homozygous).
- Brown eyes are a dominant trait, blue eyes are a recessive trait. To have blue eyes, you must inherit two copies of the blue eye allele, one from each parent.
- Codominance occurs when both alleles are dominant, and both traits are expressed equally. An example is blood type AB.
Sex-Linked Genes
- Certain genes are located on the sex chromosomes (X).
- These genes are passed down with the X chromosome from either the mother or father to a child, depending on the sex of the child in question.
- Females have two X chromosomes and males have one X and one Y chromosome.
- Females have two alleles for sex-linked genes, and males have one.
- Sex-linked genetic diseases like haemophilia are often recessive, meaning that in females two copies are needed to show the disease.
- Males only need one copy of the recessive gene to display the sex-linked trait. This makes sex-linked traits more common in males than in females.
- Haemophilia is a disease caused by a sex-linked gene that is recessive.
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Description
Test your understanding of dominant and recessive alleles as well as sex-linked genes. This quiz covers basic genetic concepts, inheritance patterns, and examples such as eye color and blood types. Explore how traits are passed down through generations based on allelic interactions.
