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Patterns of Inheritance quiz

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  • What does Mendel's law of segregation state about allele separation during gamete formation?
    It states that alleles for a gene separate so each gamete receives only one allele, resulting in haploid gametes.
  • During which phase of meiosis does independent assortment occur, and what does it result in?
    It occurs during metaphase I of meiosis I and results in genetic diversity by allowing random alignment of homologous chromosomes.
  • How does the law of independent assortment contribute to genetic diversity?
    It allows alleles of different genes to segregate independently, creating gametes with all possible combinations of alleles.
  • What is incomplete dominance, and what phenotype does it produce in heterozygotes?
    Incomplete dominance is when heterozygotes show a blended, intermediate phenotype between the two alleles.
  • How does codominance differ from incomplete dominance in terms of phenotype expression?
    In codominance, both alleles are equally and fully expressed in patches, rather than blending into an intermediate phenotype.
  • Which human trait is a classic example of codominance, and what are the codominant alleles involved?
    Human ABO blood type is a classic example, with IA and IB alleles being codominant.
  • What is epistasis, and how does it affect blood type expression?
    Epistasis is when one gene affects the expression of another; for example, a nonfunctional H protein gene prevents A or B molecules from attaching to red blood cells, resulting in type O blood regardless of IA or IB alleles.
  • What is a polygenic trait, and give an example?
    A polygenic trait is a single phenotypic trait affected by multiple genes, such as human height.
  • What is pleiotropy, and provide an example?
    Pleiotropy is when one gene affects multiple phenotypic traits; Marfan syndrome is an example, where a mutation in one gene affects many body systems.
  • In a pedigree chart, what do circles and squares represent, and what does shading indicate?
    Circles represent females, squares represent males, and shading indicates individuals affected by the phenotype of interest.
  • What is the difference between autosomal and sex-linked inheritance?
    Autosomal inheritance involves genes on non-sex chromosomes, while sex-linked inheritance involves genes on the X or Y chromosomes.
  • Why are X-linked traits more commonly expressed in males than females?
    Males have only one X chromosome, so they express whatever allele is present, while females have two X chromosomes and can be carriers without expressing the trait.
  • What is X inactivation, and what is a Barr body?
    X inactivation is the random turning off of one X chromosome in female cells, and the inactive X chromosome is called a Barr body.
  • How does X inactivation explain the patchy fur color in calico cats?
    Random X inactivation in female cats leads to different fur color alleles being expressed in different cells, resulting in color patches.
  • What is the probability of having a male or female child, and why?
    There is a 50% chance for each, because males contribute either an X or Y chromosome, while females always contribute an X.