Genetic Inheritance and Mendel's Experiments
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Questions and Answers

What is the primary focus of Gregor Mendel's experiments?

  • The effects of environmental changes on plants
  • The method of plant cross-breeding and trait inheritance (correct)
  • The role of human behavior in genetic expression
  • The process of photosynthesis in pea plants

    • What does a Punnett square illustrate?

  • The physical appearance of the offspring
  • The history of traits in previous generations
  • The genotypes and their probabilities in offspring (correct)
  • The possibility of environmental influences on genetics

    • In Mendel's experiments with purple and white flowers, what ratio did he find in the offspring's phenotypes?

  • 1:1
  • 2:1
  • 4:1
  • 3:1 (correct)

    • To express a recessive genetic disorder, an individual must be what?

    <p>Homozygous recessive</p> Signup and view all the answers

    Which of the following statements about alleles is true?

    <p>Only one allele is inherited from each parent</p> Signup and view all the answers

    Which of the following is an example of a recessive genetic disorder?

    <p>Cystic fibrosis</p> Signup and view all the answers

    What do sperm and egg cells contain in terms of genetic information?

    <p>Only one copy of each chromosome pair</p> Signup and view all the answers

    Which factor can influence genetic expression besides heredity?

    <p>Environmental factors</p> Signup and view all the answers

    What term is used to refer to individuals who carry one copy of a faulty allele for a recessive genetic disorder?

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

    If a father is affected by a dominant genetic disorder and the mother is unaffected, what is the probability of their offspring being affected?

    <p>50%</p> Signup and view all the answers

    Which genotype represents an individual with normal pigmentation who is also a carrier for albinism?

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

    What is a characteristic of recessive genetic disorders in a pedigree?

    <p>Carriers can be unaffected.</p> Signup and view all the answers

    In the case of Huntington's Chorea, what can be inferred about the inheritance pattern of this disorder?

    <p>Individuals with the disorder express it if they carry one or two dominant alleles.</p> Signup and view all the answers

    Which of the following represents an offspring genotype of two unaffected parents in a pedigree for a dominant trait?

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

    What kind of trait is albinism classified as in genetic terms?

    <p>Recessive autosomal trait</p> Signup and view all the answers

    Which of the following phenotypes corresponds to the homozygous dominant genotype in the case of albinism?

    <p>Normal pigmentation</p> Signup and view all the answers

    Which statement about recessive traits is true?

    <p>Unaffected parents can have affected offspring.</p> Signup and view all the answers

    What is the result of a cross between two heterozygous individuals (Aa x Aa) for a recessive trait?

    <p>25% of offspring will show the affected phenotype.</p> Signup and view all the answers

    In a scenario where incomplete dominance occurs, what phenotype would an SC genotype exhibit?

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

    What does codominance mean in the context of blood types?

    <p>Phenotypes of both alleles are expressed together.</p> Signup and view all the answers

    If a person has genotype IB i for blood type, what phenotype would they exhibit?

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

    For the gene controlling hair texture, what would the expected phenotype of a genotype CC be?

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

    What is a characteristic of a complete dominance scenario?

    <p>An individual with one dominant allele always shows the dominant trait.</p> Signup and view all the answers

    In the ABO blood group system, how many alleles can control the blood type?

    <p>Three alleles</p> Signup and view all the answers

    What is the probability of a man with blood type A (heterozygous) and a woman with blood type AB having a child with blood type B?

    <p>50%</p> Signup and view all the answers

    Why do males express recessive X-linked traits more often than females?

    <p>Males only have one X chromosome.</p> Signup and view all the answers

    Which of the following statements is true regarding X-linked characters?

    <p>Females can be carriers of X-linked traits.</p> Signup and view all the answers

    What is Duchenne muscular dystrophy caused by?

    <p>A recessive mutation on the X chromosome.</p> Signup and view all the answers

    In terms of inheritance, how do daughters inherit X chromosomes?

    <p>One from each parent.</p> Signup and view all the answers

    What is a common example of an X-linked human disorder?

    <p>Hemophilia.</p> Signup and view all the answers

    How many sex chromosomes do females have?

    <p>Two X chromosomes.</p> Signup and view all the answers

    What is the role of the sex chromosome in determining biological sex?

    <p>It determines the biological sex of the child.</p> Signup and view all the answers

    What determines whether a son will be colour blind if his mother is a carrier?

    <p>The combination of both parents' genotypes</p> Signup and view all the answers

    What is the probability that a son will be colour blind if his mother is a carrier and his father has normal vision?

    <p>50%</p> Signup and view all the answers

    How does Androgen Insensitivity Syndrome (AIS) affect a genetic male's phenotype?

    <p>It causes female external genitals despite genetic male status</p> Signup and view all the answers

    What factor influences the phenotypic expression of height in humans?

    <p>A combination of genetic and environmental factors</p> Signup and view all the answers

    What is the inheritance mode of colour blindness?

    <p>X-linked recessive</p> Signup and view all the answers

    In individuals with complete Androgen Insensitivity Syndrome, which characteristic is expected?

    <p>Presence of testes in the abdomen</p> Signup and view all the answers

    What is the expected carrier probability for a child when one parent is colour blind and the other has normal vision?

    <p>25%</p> Signup and view all the answers

    Which statement accurately describes partial Androgen Insensitivity Syndrome?

    <p>Can result in genitalia with male and female characteristics</p> Signup and view all the answers

    What role do environmental factors play in gene expression?

    <p>They can alter the expression of genes through epigenetics.</p> Signup and view all the answers

    How does the diathesis-stress model explain the development of mental disorders?

    <p>It demonstrates the interaction between genetic predisposition and environmental stressors.</p> Signup and view all the answers

    What is one function of the genes identified in the study published in the Lancet?

    <p>Making membrane transport proteins that regulate calcium ion flow.</p> Signup and view all the answers

    What is an example of a psychological disorder that may have a genetic basis?

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

    What effect can abnormal calcium ion flow into neurons have?

    <p>It can influence neurotransmitter release.</p> Signup and view all the answers

    Which of the following statements best describes the influence of stress on genetic predisposition?

    <p>Stress can increase the likelihood of expressed genetic predispositions.</p> Signup and view all the answers

    How do identical twins demonstrate the concept of epigenetics?

    <p>They exhibit different traits due to environmental influences.</p> Signup and view all the answers

    Which statement is true regarding individuals with a family history of mental illness and environmental stress?

    <p>They have a higher vulnerability to mental illness when exposed to stress.</p> Signup and view all the answers

    Study Notes

    Genetic Inheritance

    • Gregor Mendel is considered the father of modern genetics
    • Mendel experimented with pea plants to study how traits are passed from one generation to the next
    • He cross-bred plants with specific traits, quantifying and analyzing the offspring's phenotypes (observable traits).

    Mendel's Experiment

    • Mendel's experiment involved crossing true-breeding (homozygous) plants (e.g., purple flowers x white flowers)
    • The F1 generation: all offspring displayed the dominant trait (purple flowers)
    • The F2 generation showed a 3:1 ratio of dominant to recessive traits (purple flowers to white flowers)

    Offspring Inheritance

    • Offspring inherit one allele from each parent
    • Sperm and egg cells each contain only one copy of each chromosome pair, hence one allele for each gene
    • The example given involves gene A with genotype Aa and a 50/50 chance of inheriting either allele.

    Punnett Square

    • A Punnett square is a grid used to predict the possible genotypes and phenotypes of offspring.
    • Rows represent possible gametes generated by parent 1
    • Columns represent possible gametes generated by parent 2
    • Boxes represent the possible genotypes of resulting offspring

    Recessive Genetic Disorders

    • To display a recessive disorder, an individual must be homozygous recessive for the faulty gene.
    • The faulty gene produces incorrect or absent proteins required to function correctly
    • Examples of recessive disorders include Albinism, Cystic Fibrosis, and Sickle-cell Disease

    Dominant Genetic Disorders

    • A dominant genetic disorder appears if an individual has one or two dominant alleles.
    • Examples include Achondroplasia (a form of dwarfism), Polydactyly (extra fingers/toes), and Huntington's Chorea (a degenerative disease)

    Genetic Pedigree

    • Genetic pedigrees are family trees used to follow the inheritance of a gene or trait.
    • More useful in tracking recessive traits because affected offspring can have unaffected traits in the pedigree (carriers)

    Levels of Dominance

    • Complete dominance: the presence of a dominant allele masks the expression of a recessive allele.
      • Example: Brown eyes are dominant over blue eyes. Heterozygous individuals have brown eyes.
    • Incomplete dominance: neither allele is completely dominant. Heterozygous individuals have intermediate phenotypes between the two homozygous forms.
      • Example: Wavy hair is an example of incomplete dominance.
    • Codominance: both alleles are expressed in the phenotype.
      • Example: ABO blood groups. IA and IB are codominant, and i (allele) is recessive to both

    Multiple Alleles

    • Most genes exhibit more than two possible alleles. Examples include blood type
      • A, B, and i are the alleles responsible for ABO blood groups
      • Note that in heterozygous individuals, all alleles are present in the blood, just two are the result for phenotype.

    Sex Chromosomes

    • Humans have two sex chromosomes: XX for females and XY for males.
    • Sex chromosomes contain genes determining sex.
      • Genes related to sex characteristics
      • Also genes to determine other characteristics distinct from the role in biological sex determination.

    Sex Determination

    • The sex chromosome present in the sperm determines the child's biological sex.
    • If the sperm contains X, the child will be female, and if the sperm contains Y, the child will be male.

    X-Linked Characters

    • Genes located on the X chromosome determine X-linked characters.
    • Males express recessive X-linked traits more frequently than females because they only have one X chromosome.
    • Daughters can receive an X-chromosome from each parent, but can be carriers.

    X-Linked Human Disorders

    • Examples of X-linked disorders include Hemophilia, Duchenne muscular dystrophy, and color blindness.

    Nature and Nurture

    • Environmental factors influence expression of genes

    Identical Twin Studies

    • Identical twins have the same genetic makeup (genome) but may have different phenotypes due to diverse environmental experiences.

    Epigenetics

    • Epigenetic changes alter how genes are expressed by adding molecules attached to chromosomes, effectively switching genes on or off

    Mental Health and Genes

    • Psychological Disorders often have a genetic basis; family members may exhibit a predisposition for particular diseases
    • However, environmental factors heavily influence a person's likelihood of expressing the disease and developing said disease.
    • 2013 study linked specific genes to various mental illnesses (schizophrenia, bipolar disorder, autism spectrum disorder)

    Diathesis-Stress Model

    • A model that shows the relationship between predisposition (diathesis) and environmental factors (stressors)

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    Behavioral Biology Lecture 13: Genetic Inheritance PDF

    Description

    Explore the fundamentals of genetic inheritance through Gregor Mendel's groundbreaking experiments with pea plants. This quiz covers key concepts such as the F1 and F2 generations, allele inheritance, and the application of Punnett squares. Test your understanding of how traits are passed down through generations.

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