Mendel's Principles of Inheritance Quiz
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Questions and Answers

What phenotypic ratio is expected in the offspring from a cross between a homozygous solid-winged dad and a homozygous polka-dotted mom?

  • 1 solid : 0 polka-dotted
  • All polka-dotted
  • 1 polka-dotted : 1 solid
  • All solid (correct)
  • Which of the following best describes the principle of incomplete dominance?

  • The phenotype is a blend of both alleles. (correct)
  • One allele completely masks the effect of another.
  • The trait is influenced by multiple alleles at once.
  • Both alleles are fully expressed in the phenotype.
  • How many alleles can an individual inherit for a single gene that has multiple alleles?

  • Three
  • Four
  • One
  • Two (correct)
  • In which genetic phenomenon do multiple genes influence a single trait?

    <p>Polygenic traits</p> Signup and view all the answers

    Which of the following statements is true regarding the inheritance of traits with multiple alleles?

    <p>Phenotypic expression can be limited due to dominance relationships.</p> Signup and view all the answers

    What is the expected outcome for daughters when a colorblind dad mates with a mom with normal vision?

    <p>50% daughters will be carriers, 50% will be unaffected.</p> Signup and view all the answers

    How does inbreeding primarily affect a population genetically?

    <p>It increases the likelihood of recessive alleles being expressed.</p> Signup and view all the answers

    What is a consequence of inbreeding in dog breeds?

    <p>Perpetuation of desirable traits in subsequent generations.</p> Signup and view all the answers

    What might be a safeguard against inbreeding in human populations?

    <p>Encouraging migrations from neighboring populations.</p> Signup and view all the answers

    What type of inheritance pattern is observed when a red carnation and a white carnation produce all pink offspring?

    <p>Incomplete dominance.</p> Signup and view all the answers

    In a TT x Tt cross, what is the expected ratio of tall to short plants?

    <p>3:1</p> Signup and view all the answers

    What requirement must be met for expressing an autosomal recessive disease?

    <p>Both parents must carry the recessive allele.</p> Signup and view all the answers

    What led to the genetic problems associated with the Hapsburg family and Queen Victoria's lineage?

    <p>Inbreeding due to close familial relationships.</p> Signup and view all the answers

    What does a diploid organism possess in terms of chromosomes?

    <p>Two copies of each chromosome, one from each parent.</p> Signup and view all the answers

    Which of the following best describes the function of a gene?

    <p>It is a part of DNA that directs specific protein manufacture.</p> Signup and view all the answers

    What characterizes a recessive allele?

    <p>It requires two copies to be expressed in the phenotype.</p> Signup and view all the answers

    How are homozygous and heterozygous individuals differentiated?

    <p>Homozygous individuals have two identical alleles, while heterozygous have two different alleles.</p> Signup and view all the answers

    What role do mutations play in the formation of different alleles?

    <p>They randomly modify the sequence of bases in a gene.</p> Signup and view all the answers

    What is a characteristic trait of dominant alleles?

    <p>They suppress the effects of recessive alleles.</p> Signup and view all the answers

    What is the phenotype of an individual primarily determined by?

    <p>The allelic makeup of the organism.</p> Signup and view all the answers

    In a genetic cross, what is the purpose of the controlled mating experiment?

    <p>To examine the inheritance of specific traits.</p> Signup and view all the answers

    What does Mendel's Law of Segregation state about alleles during gamete formation?

    <p>Each gamete carries only one of the two alleles from a gene.</p> Signup and view all the answers

    In a cross between true-breeding plants with purple flowers (YY) and white flowers (yy), which generation will be heterozygous?

    <p>F1 generation</p> Signup and view all the answers

    Which of the following describes the concept of dominant alleles as stated by Mendel?

    <p>Dominant alleles show their effects even when paired with recessive alleles.</p> Signup and view all the answers

    What ratio of dominant to recessive phenotypes is typically expected in the F2 generation?

    <p>3:1</p> Signup and view all the answers

    What is indicated by the term 'filial' in genetics as used by Mendel?

    <p>It refers to the generations that come from a cross between parental organisms.</p> Signup and view all the answers

    Which principle states that genes do not influence each other's sorting into gametes?

    <p>Law of Independent Assortment</p> Signup and view all the answers

    When crossing two heterozygous plants (Pp), what are the possible genotypes for their offspring?

    <p>PP, Pp, pp</p> Signup and view all the answers

    If a trait is controlled by alleles that show complete dominance, how would an organism with two recessive alleles appear?

    <p>It would express the recessive phenotype.</p> Signup and view all the answers

    How does a Punnett square help in genetic crosses?

    <p>It determines the actual probabilities of different genotypes and phenotypes among offspring.</p> Signup and view all the answers

    Which blood type combination would indicate a child has an AB blood type?

    <p>IAi and IBi</p> Signup and view all the answers

    What is the main difference between codominance and incomplete dominance in genetic traits?

    <p>Codominance shows both parental traits equally, while incomplete dominance produces a blend.</p> Signup and view all the answers

    In the context of epistasis, what is the primary role of Gene C as described?

    <p>Gene C suppresses the traits presented by Gene B.</p> Signup and view all the answers

    Which of the following describes pleiotropy correctly?

    <p>A single gene affects multiple traits or characteristics.</p> Signup and view all the answers

    Which of the following traits is considered polygenic?

    <p>Height</p> Signup and view all the answers

    How would a parent with a whole chromosome defect, such as Down Syndrome, affect their child's genetic inheritance?

    <p>The disorder can appear in the child without the parent showing symptoms.</p> Signup and view all the answers

    Which statement regarding the influence of environment on polygenic traits is true?

    <p>Polygenic traits may be modified by environmental factors.</p> Signup and view all the answers

    What characterizes the blood type of an individual with genotype IBi?

    <p>Type B blood</p> Signup and view all the answers

    What genetic disorder is caused by a mutation in the Fibrillin 1 gene?

    <p>Marfan's syndrome</p> Signup and view all the answers

    What could lead to a person with Type O blood having a child with Type AB blood?

    <p>The Type O parent is a carrier of the A allele.</p> Signup and view all the answers

    Study Notes

    Mendel's Principles of Inheritance

    • Mendel proposed that offspring inherit two "units" of genetic information - one from each parent, called alleles.
    • One allele is inherited from the egg (mother), and one from the sperm (father).
    • These units combine to form the offspring's genotype.

    Genetic Crosses

    • A true-breeding plant is one that produces offspring with the same phenotype as the parent.
    • The P generation refers to the true-breeding parental plants.
    • The F1 generation is the first filial generation.
    • The F2 generation is the second filial generation.
    • The F2 generation demonstrates a predictable ratio of dominant to recessive phenotypes (3:1).

    Summary of Mendel's Concepts

    • Alternative versions of genes cause variation in inherited traits.
    • Offspring inherit one copy of a gene from each parent.
    • A dominant allele has exclusive control over the phenotype when paired with a different allele (Law of Dominance).
    • Two copies of a gene segregate during meiosis and end up in different gametes (Law of Segregation).
    • Genes do not influence each other regarding the sorting of alleles into gametes (Law of Independent Assortment).
    • Gametes fuse during fertilization without regard to the alleles they carry.

    Law of Segregation

    • The Law of Segregation can be illustrated using a Punnett square.
    • The genotypes of each parent are listed, and alleles are segregated to represent the gametes.
    • A Punnett square shows the probability of genotypes and phenotypes in the offspring.

    Incomplete Dominance

    • Incomplete dominance occurs when the heterozygote displays an intermediate phenotype.
    • Neither allele exerts its full effect on the phenotype.
    • If heterozygous offspring are bred, the parental features reappear. (e.g., red + white snapdragons produce pink flowers).

    Multiple Alleles

    • Multiple alleles exist when there are three or more alleles for a gene (but an individual still inherits only two).
    • Example: Human blood groups have three alleles: IA, IB, and i.
    • These alleles produce four blood groups: A, B, AB, and O.

    Codominance

    • Codominance occurs when both parental alleles are equally visible in the heterozygote.
    • Both parental phenotypes are expressed together in the offspring.
    • Human blood groups show codominance. For example:
      • IAIA or IAi = Type A
      • IBIB or IBi = Type B
      • IAIB = Type AB
      • ii = Type O

    Epistasis

    • Epistasis refers to the interaction of genes where the phenotypic effect of alleles of one gene is dependent on the alleles present for another gene.
    • Example: In mice, coat color is determined by Gene B:
      • BB or Bb = black
      • bb = brown
    • Gene C also influences coat color:
      • CC or Cc = the color determined by Gene B.
      • cc = white, regardless of Gene B alleles.
    • Gene C is epistatic to Gene B.

    Pleiotropy

    • Pleiotropy occurs when a single gene influences multiple traits.
    • Example: Albinism affects different traits such as:
      • Absence or reduced melanin production
      • Skin color
      • Vision problems
    • Albino mice are white because of epistatic effects of Gene C on Gene B.

    Polygenic Traits

    • Polygenic traits are determined by two or more genes.
    • They result in a continuous distribution of the range of traits (e.g., body size, height, skin color).
    • Skin color is influenced by at least three genes that control melanin production and environmental factors.

    Human Genetic Disorders

    • Human genetic disorders can arise from gene or whole chromosome defects.
    • For a disorder to be inherited, the parent can:
      • Show and have the disorder.
      • Be asymptomatic and a carrier for the disorder.
      • Not have the disorder seen in the child because it is a whole chromosome condition and not allele-based.

    Genetic Testing

    • Genetic testing can be used to determine if an individual carries a gene for a specific disorder.
    • For example, a colorblind dad and a mom with normal vision can have offspring with the following outcomes:
      • Girls are carriers for the disorder.
      • Boys are affected by the disorder.

    Inbreeding

    • Inbreeding is the mating of closely related organisms by ancestry.
    • It increases the risk of recessive alleles remaining in the population.
    • This is more likely to occur in small or isolated populations.
    • Examples of inbreeding include:
      • Dog breeds
      • The Habsburg family
      • Queen Victoria of England
      • Racehorses

    Essential Terms in Genetics

    • Diploid: having two copies of each chromosome, one paternal and one maternal. In humans, 2n = 46.
    • Haploid: reproductive cells have only one copy of each chromosome (in humans, n = 23).
    • Gene: portion of DNA that governs one or more genetic traits.
    • Allele: an alternative version of a gene.
    • Genotype: the allelic makeup responsible for an individual's phenotype.
    • Phenotype: the expression of a genetic trait.

    Somatic Cells are Diploid

    • Somatic cells are body cells that have two sets of chromosomes (one from each parent).
    • This makes them diploid.

    Alleles in an Individual

    • Dominant allele: exerts control over the phenotype.
    • Recessive allele: has no effect on the phenotype when paired with a dominant allele.
    • Homozygote: an individual with two copies of the same allele.
    • Heterozygote/Heterozygous: an individual with two different alleles.

    Mutations in Alleles

    • Different alleles arise from mutations, changes in the DNA that make up a gene.
    • Mutations can be harmful, neutral, or beneficial.
    • Harmful mutations tend to be recessive alleles.
    • Neutral mutations produce almost identical protein to the original.
    • Beneficial mutations improve function.

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    Description

    Test your knowledge on Mendel's principles of inheritance, including the concepts of alleles, genetic crosses, and the F1 and F2 generations. Understand how traits are inherited and the significance of dominant and recessive alleles. This quiz covers the essential foundations of genetics as proposed by Gregor Mendel.

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