Mendel's Laws of Inheritance
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Questions and Answers

What is a monohybrid cross in the context of Mendel's experiment?

  • Mating between individuals with heterogeneous genotypes
  • Mating between individuals with heterogeneous phenotypes
  • Mating between individuals that differed in only one trait (correct)
  • Mating between individuals with multiple traits

    • What is the genotype of a true-breeding plant?

  • Heterozygous
  • Homozygous recessive
  • Homozygous dominant
  • Homozygous (correct)

    • What is the purpose of a test cross?

  • To identify the genotype of an individual with a recessive phenotype
  • To identify the genotype of an individual with a dominant phenotype (correct)
  • To identify the phenotype of an individual with a recessive genotype
  • To identify the genotype of an individual with a heterozygous genotype

    • What is the Law of Dominance?

    <p>The law that states that dominant alleles are always expressed in a heterozygous condition</p> Signup and view all the answers

    What is the purpose of a Punnett square?

    <p>To predict the genotypes of a particular cross or breeding experiment</p> Signup and view all the answers

    What is an allele?

    <p>One of two or more alternative forms of a gene</p> Signup and view all the answers

    What is the difference between a heterozygous and homozygous genotype?

    <p>Heterozygous has two different alleles, while homozygous has two identical alleles</p> Signup and view all the answers

    What is the generation that is the offspring of the parental generation?

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

    Why was the garden pea used in Mendel's experiment?

    <p>Because it is easy to cultivate and has a short generation time</p> Signup and view all the answers

    What is the term for the physical expression of a trait?

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

    What proportion of offspring are expected to be albino in a monohybrid testcross?

    <p>1/4</p> Signup and view all the answers

    What is the genotype of a homozygous normal individual in the albinism example?

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

    In the dog example, what is the genotype of the smooth-haired female?

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

    What is the phenotype of a heterozygous individual in the rabbit example?

    <p>Short hair</p> Signup and view all the answers

    What is the expected ratio of wire-haired to smooth-haired dogs in the F1 generation?

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

    In the rabbit example, what is the probability of a bunny being homozygous for the short hair allele?

    <p>1/4</p> Signup and view all the answers

    What is the genotype of a homozygous affected individual in the albinism example?

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

    What is the primary factor that affects the expression of a gene?

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

    What is the term for a trait that is located on one of the two sex chromosomes?

    <p>Sex-linked trait</p> Signup and view all the answers

    What is the purpose of a pedigree in analyzing human inheritance?

    <p>To analyze the pattern of inheritance of a particular trait throughout a family</p> Signup and view all the answers

    What is the term for a gene that is phenotypically expressed over another allele?

    <p>Dominant allele</p> Signup and view all the answers

    What is the relationship between genotype and phenotype?

    <p>Genotype + environment = phenotype</p> Signup and view all the answers

    What is the term for the genetic makeup of an individual?

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

    What is the pattern of inheritance in which a single allele is sufficient to express the trait?

    <p>Autosomal dominant</p> Signup and view all the answers

    What is the purpose of pedigree analysis in human inheritance?

    <p>All of the above</p> Signup and view all the answers

    What is a common characteristic of individuals with Down syndrome?

    <p>Mental retardation</p> Signup and view all the answers

    What is the characteristic of Klinefelter syndrome?

    <p>Extra X chromosome</p> Signup and view all the answers

    Which syndrome is exclusive to females?

    <p>Turner syndrome</p> Signup and view all the answers

    What is a possible effect of Turner syndrome?

    <p>Failure of ovaries to develop</p> Signup and view all the answers

    What is the chromosomal makeup of an individual with Klinefelter syndrome?

    <p>47, XXY</p> Signup and view all the answers

    What is a common physical characteristic of individuals with Turner syndrome?

    <p>Short height</p> Signup and view all the answers

    What can a pedigree be used to determine?

    <p>The way certain alleles are inherited</p> Signup and view all the answers

    How do you determine if a trait is dominant or recessive when reading a pedigree?

    <p>By seeing if one of the parents has the trait</p> Signup and view all the answers

    What is a characteristic of autosomal traits?

    <p>Both males and females are equally affected</p> Signup and view all the answers

    What is the difference between autosomal and sex-linked traits?

    <p>Autosomal traits affect both males and females, while sex-linked traits affect only one sex</p> Signup and view all the answers

    What is the characteristic of an autosomal dominant trait?

    <p>A single copy of the mutated gene is enough to cause the disorder</p> Signup and view all the answers

    How do you determine if a pedigree shows an autosomal or sex-linked trait?

    <p>By comparing the traits of the males and females</p> Signup and view all the answers

    What is the probability of a male being affected by an X-linked recessive trait?

    <p>More than a female</p> Signup and view all the answers

    What is the location of the gene in an autosomal dominant trait?

    <p>On one of the autosomes</p> Signup and view all the answers

    Study Notes

    Patterns of Inheritance

    • Traits are controlled by a pair of genes (alleles)
    • Three main laws of inheritance:
      • Law of Dominance
      • Law of Segregation
      • Law of Independent Assortment

    Mendel's Experiment

    • Used garden pea plants (Pisum sativum) for easy cultivation and short generation time
    • Performed cross-breeding experiments between true-breeding plants
    • True-breeding plants have parents with a certain trait that consistently pass it to every offspring (homozygous)
    • Monohybrid cross: mating individuals that differ in only one trait
    • Performed reciprocal crosses: individuals pollinate one another
    • Generations: P (parental), F1 (first generation offspring), F2 (second generation offspring)

    Key Terms

    • Phenotype: observable traits
    • Genotype: set of alleles in an individual's chromosomes
    • Homozygous: same allele of a gene on both homologous chromosomes
    • Heterozygous: hybrid, different forms of an allele
    • Allele: one of two or more alternative forms of a gene
    • Punnett square: a square diagram used to predict the genotypes of a particular cross or breeding experiment
    • Test cross: an experimental cross of an individual organism with a dominant phenotype but unknown genotype and an organism with a homozygous recessive genotype and phenotype

    Laws of Inheritance

    • Law of Dominance: in a heterozygous condition, the allele whose characters are expressed over the other allele is called the dominant allele
    • Example: albinism, probability of a child having albinism

    Monohybrid Testcross

    • Example: wire-haired and smooth hair in dogs
    • Example: short hair and long hair in rabbits

    Polygenic Inheritance

    • Example: fur color in Labrador

    Nature vs Nurture

    • Environment affects the expression of a gene, which in turn affects the phenotype
    • Genotype + environment = phenotype

    Inheritance Patterns in Humans

    • Autosomal dominant
    • Autosomal recessive
    • X-linked dominant
    • X-linked recessive

    Pedigree Analysis

    • Used to analyze the pattern of inheritance of a particular trait throughout a family
    • Shows the presence or absence of a trait as it relates to the relationship among parents, offspring, and siblings
    • By analyzing a pedigree, we can determine genotypes, identify phenotypes, and predict how a trait will be passed on in the future

    Reading a Pedigree

    • Determine whether the trait is dominant or recessive
    • Determine if the chart shows an autosomal or sex-linked (usually X-linked) trait
    • Autosomal traits: both males and females are equally likely to be affected
    • X-linked traits: males are more commonly affected than females

    Autosomal Dominant

    • The gene in question is located on one of the autosomes (non-sex chromosomes)
    • A single copy of the mutated gene (from one parent) is enough to cause the disorder
    • Traits appear whether the individual is heterozygous or homozygous
    • Affects both males and females
    • Example: Down syndrome

    Klinefelter Syndrome

    • Occurs when males have an extra X chromosome (47, XXY)
    • Can inhibit growth of genitalia, hormone production, and fertility

    Turner Syndrome

    • A condition that affects only females, resulting from one of the X chromosomes (sex chromosomes) being missing or partially missing (45, XO)
    • Can cause a variety of medical and developmental problems, including short height, failure of ovaries to develop, and heart defects

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    Description

    This quiz covers the fundamental principles of genetics, including the Law of Dominance, Law of Segregation, and Law of Independent Assortment, as discovered by Gregor Mendel through his experiments on garden peas.

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