Genetics Chapter: Independent Assortment and Meiosis
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Questions and Answers

What does the term 'genotype' specifically refer to in genetics?

  • The environmental factors affecting an organism's traits
  • The physical appearance of an organism
  • The trait that is expressed in the presence of a dominant allele
  • The genetic composition of an organism (correct)

    • In a monohybrid cross between a homozygous tall plant (TT) and a homozygous dwarf plant (tt), what will be the genotype of the F1 generation?

  • Tt (correct)
  • tt
  • TtTt
  • TT

    • Which of the following best describes a dominant allele?

  • An allele that appears only in a homozygous state
  • An allele that is masked by a recessive allele
  • An allele that is always expressed in the phenotype (correct)
  • An allele that contributes equally with another in a heterozygous condition

    • What is the purpose of a Punnett square in genetics?

    <p>To predict the traits of offspring resulting from genetic crosses</p> Signup and view all the answers

    In the context of a monohybrid cross, what does the F2 generation refer to?

    <p>The second generation of offspring from a genetic cross</p> Signup and view all the answers

    What does the principle of independent assortment state regarding gene pairs?

    <p>Gene pairs segregate independently during gamete formation.</p> Signup and view all the answers

    What type of cross is performed to determine the genotype of an individual with unknown genotype?

    <p>Test cross</p> Signup and view all the answers

    If a test cross results in a 50% proportion of both purple and white flowers, what can be concluded about the unknown genotype?

    <p>It is heterozygous.</p> Signup and view all the answers

    In incomplete dominance, what phenotype is expressed in the offspring when red and white snapdragons are crossed?

    <p>Pink flowers</p> Signup and view all the answers

    What will be the phenotypic ratio in the F2 generation after self-pollinating pink snapdragons resulting from a red and white cross?

    <p>1:2:1 red, pink, white</p> Signup and view all the answers

    Which of the following best describes the relationship between meiosis and allele segregation?

    <p>Chromosome movement in meiosis correlates with allele segregation.</p> Signup and view all the answers

    How can one determine if a tall, purple plant is homozygous or heterozygous for those traits?

    <p>By performing a test cross with a homozygous recessive plant.</p> Signup and view all the answers

    Which scenario exemplifies incomplete dominance in genetics?

    <p>Traits blend together to form an intermediate phenotype.</p> Signup and view all the answers

    What is the genotypic ratio of the offspring when Tt is crossed with Tt?

    <p>1:2:1</p> Signup and view all the answers

    Which of the following describes the phenotypic outcome of a monohybrid cross Tt x Tt?

    <p>3 tall, 1 dwarf</p> Signup and view all the answers

    When crossing a homozygous tall (TT) with a homozygous dwarf (tt), what is the expected phenotype of the offspring?

    <p>100% tall</p> Signup and view all the answers

    What is the phenotype of the offspring resulting from a cross between Tt and tt?

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

    What do the gametes of a homozygous tall parent (TT) produce in a Punnett Square?

    <p>Only T</p> Signup and view all the answers

    In a monohybrid cross, if one parent is TT and the other is tt, what genotypes will result?

    <p>All Tt</p> Signup and view all the answers

    If both parents are heterozygous (Tt), what percentage of the offspring will be homozygous?

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

    What is the significance of splitting the genotypes of parents when using a Punnett Square?

    <p>To identify all possible gametes</p> Signup and view all the answers

    What is the ratio of phenotypes observed in the F2 generation of a dihybrid cross involving flower color and stem length?

    <p>9:3:3:1</p> Signup and view all the answers

    Which of the following is a characteristic of Gaucher Disease?

    <p>It causes a lipid-storage disorder.</p> Signup and view all the answers

    What phenotype ratio corresponds to the genotype ratio of 9:3:3:1 in dihybrid crosses?

    <p>Tall, purple: Tall, white: Short, purple: Short, white</p> Signup and view all the answers

    In a dihybrid cross, which of the following represents dominant alleles?

    <p>T and P</p> Signup and view all the answers

    What is the incidence of Gaucher Disease in the general population?

    <p>1 in 100,000</p> Signup and view all the answers

    Which phenotype is expected from a parental cross of TT PP and tt pp?

    <p>All tall, purple flowers</p> Signup and view all the answers

    Which genetic principle states that alleles for different traits are passed independently of one another?

    <p>Principle of independent assortment</p> Signup and view all the answers

    How many different genotypes can arise from a dihybrid cross?

    <p>9</p> Signup and view all the answers

    In a dihybrid cross of Tt Pp x Tt Pp, how many phenotypes are expected?

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

    For the genotype TtPp in a dihybrid cross, what is true about its phenotype?

    <p>It expresses the dominant traits.</p> Signup and view all the answers

    What percentage of offspring from a cross between Tt and tt will be tall?

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

    In the F2 generation of a Pp x Pp cross, what is the phenotypic ratio of purple to white flowers?

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

    Which of the following statements accurately describes Mendel's Principle of Segregation?

    <p>It describes how pairs of hereditary factors separate during gamete formation.</p> Signup and view all the answers

    If two heterozygous parents for cystic fibrosis (C c) have a child, what is the probability that the child will be a carrier but not show symptoms?

    <p>1 in 2</p> Signup and view all the answers

    What is the expected genotype frequency for children of two carriers of cystic fibrosis?

    <p>1 CC, 2 Cc, 1 cc</p> Signup and view all the answers

    Which of the following is characteristic of a dominant allele?

    <p>It can be homozygous or heterozygous.</p> Signup and view all the answers

    In the inheritance pattern of cystic fibrosis, what is the expected outcome for 4 children of two carrier parents?

    <p>1 will have cystic fibrosis, 2 will be carriers, 1 normal.</p> Signup and view all the answers

    What is the probability that a child will be affected by cystic fibrosis if both parents are heterozygous?

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

    Study Notes

    Principle of Independent Assortment

    • Gene pairs segregate independently during gamete formation, contributing to genetic diversity.
    • Independent assortment allows for numerous gene combinations, enhancing the advantages of sexual reproduction.

    Meiosis and Gene Segregation

    • Chromosome movement during meiosis correlates with the segregation of alleles.

    Test Cross

    • A test cross determines the genotype of an unknown individual by crossing it with a homozygous recessive individual.
    • For example, crossing a purple flower (PP or Pp) with a white flower (pp) reveals the genotype:
      • 100% purple offspring indicates the unknown parent is PP.
      • 50% purple and 50% white offspring indicates the unknown parent is Pp.

    Incomplete Dominance

    • In cases of incomplete dominance, the heterozygous phenotype is intermediate between the two homozygous phenotypes.
    • Example: Crossing red (RR) and white (rr) snapdragons results in pink (Rr) flowers.
    • F2 generation from self-pollination of pink (Rr) leads to a 1:2:1 ratio of red, pink, and white flowers.

    Summary of Genetics

    • Chromosomes and genes occur in pairs, carrying hereditary information.
    • New gene combinations arise during sexual reproduction.
    • Key Terms:
      • Monohybrid Cross: Involves a single trait; P = parental generation, F1 = first offspring generation, F2 = second offspring generation.
      • Genotype: The genetic makeup of an organism.
      • Phenotype: The physical manifestation including environmental effects.

    Monohybrid Cross Example

    • Crossing TT (homozygous tall) with tt (homozygous dwarf) results in:
      • F1 generation: All Tt (heterozygous tall plants).
    • F2 cross of Tt with Tt results in:
      • Genotypic ratio: 1 TT : 2 Tt : 1 tt
      • Phenotypic ratio: 3 tall : 1 dwarf.

    Punnett Square

    • A Punnett square predicts offspring genotypes and phenotypes:
      • Determine parent genotypes.
      • Cross them in a square format.
      • Fill in possible genotypes and summarize results.
    • Shortcuts are available if one parent is homozygous.

    Mendel’s Principles

    • Principle of Dominance: One allele can mask the other in heterozygotes.
    • Principle of Segregation: During gamete formation, gene pairs are separated so each gamete receives one gene.

    Genetic Disorders

    • Cystic Fibrosis (CF): A recessive genetic disorder; one in 20 people of European descent are carriers.
    • Gaucher Disease: A rare genetic disorder primarily affecting individuals of Eastern European Jewish ancestry.

    Dihybrid Crosses

    • Involves parents differing in two traits simultaneously.
    • Example: Flower color (P = purple, p = white) and stem length (T = tall, t = short).
    • F1 generation from crossing TT PP with tt pp results in all Tt Pp offspring (tall and purple).
    • F2 generation shows a 9:3:3:1 phenotypic ratio (tall purple, tall white, short purple, short white).

    Dihybrid Cross Genotype Ratios

    • Nine genotypes correlate to observed phenotypes:
      • Tall purple: 9
      • Tall white: 3
      • Short purple: 3
      • Short white: 1

    Conclusion

    • Mendel's work laid the foundation for modern genetics, illustrating how traits are passed through generations and the significance of allele interactions.

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    Lecture 7: Genetics PDF

    Description

    Explore the principles of independent assortment and gene segregation in this genetics quiz. Learn how traits are inherited through test crosses and the implications of incomplete dominance. This quiz focuses on key concepts that illustrate the mechanisms behind genetic diversity during reproduction.

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