Genetics Review for Chapters 12-14
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Questions and Answers

Which of the following statements about mutations is FALSE?

  • Mutagens can be chemical or physical agents in the environment.
  • All mutations lead to significant changes in an organism's traits. (correct)
  • Some mutations can be caused by errors during DNA replication.
  • Most mutations have little or no effect on the organism.

    • What does Chargaff's Rule state about the base pairing in DNA?

  • The percentage of Guanine is equal to that of Thymine.
  • The percentages of Adenine and Thymine are equal, as are Guanine and Cytosine. (correct)
  • The percentages of all four bases are equal.
  • The percentage of Adenine is greater than Thymine.

    • Which type of mutagen includes UV light and x-rays?

  • Natural mutations
  • Physical mutagens (correct)
  • Chemical mutagens
  • Biological mutagens

    • What percentage of mutations typically affect the outcome of the protein being produced?

    <p>Approximately 10% (C)</p> Signup and view all the answers

    Why is the genetic code referred to as 'universal'?

    <p>It is consistently passed from one generation to the next across species. (A)</p> Signup and view all the answers

    Which process during meiosis contributes to genetic variation through the exchange of chromosome segments?

    <p>Crossing-over (C)</p> Signup and view all the answers

    What is the correct base pairing rule in DNA replication?

    <p>Adenine bonds with Thymine (C)</p> Signup and view all the answers

    During which phase of the cell cycle does DNA replication occur?

    <p>S phase (A)</p> Signup and view all the answers

    What role does helicase play in DNA replication?

    <p>It unzips the DNA molecule (D)</p> Signup and view all the answers

    Which structure is not a component of a nucleotide?

    <p>Helicase (A)</p> Signup and view all the answers

    What is produced at the end of meiosis?

    <p>Four genetically different haploid cells (D)</p> Signup and view all the answers

    Which term describes the segments of DNA that are exchanged during crossing-over?

    <p>Gene segments (B)</p> Signup and view all the answers

    What is the final result of the DNA replication process?

    <p>Two identical DNA molecules (D)</p> Signup and view all the answers

    What is the result of crossing two heterozygous parents for a single trait?

    <p>The offspring will exhibit a phenotypic ratio of 3:1. (C)</p> Signup and view all the answers

    What does the principle of independent assortment state?

    <p>Genes for different traits segregate independently during gamete formation. (D)</p> Signup and view all the answers

    What describes a diploid cell?

    <p>A cell that has both homologous chromosomes. (D)</p> Signup and view all the answers

    How many rounds of cell division occur in meiosis?

    <p>Two, resulting in four cells. (C)</p> Signup and view all the answers

    Which process results in genetically identical cells?

    <p>Mitosis, which features single cell division. (D)</p> Signup and view all the answers

    What is the primary purpose of meiosis?

    <p>To generate genetic diversity and reduce chromosome number. (B)</p> Signup and view all the answers

    What term describes the different forms of a gene?

    <p>Alleles (D)</p> Signup and view all the answers

    In the context of Mendel's experiments, what does the F1 generation represent?

    <p>The first filial generation produced by a cross. (D)</p> Signup and view all the answers

    What is the main function of a Punnett square in genetic studies?

    <p>To predict the possible gene combinations that offspring may inherit (A)</p> Signup and view all the answers

    If a homozygous round pea plant (RR) is crossed with a homozygous wrinkled pea plant (rr), what will be the genotype of their offspring?

    <p>Rr (B)</p> Signup and view all the answers

    Which of the following statements about alleles is NOT correct?

    <p>All traits expressed in offspring originate solely from the homozygous parent. (C)</p> Signup and view all the answers

    In Mendel's experiments, what was the significance of analyzing only one or two traits at a time?

    <p>It allowed for clear observation of dominance relationships. (C)</p> Signup and view all the answers

    In the context of genetic inheritance, what does the term 'heterozygous' mean?

    <p>An organism with two different alleles for a trait. (D)</p> Signup and view all the answers

    What is meant by the Principle of Dominance in genetics?

    <p>A dominant allele can mask the expression of a recessive allele. (D)</p> Signup and view all the answers

    What might indicate that a trait not seen in the parent generation appears in the offspring?

    <p>At least one parent is heterozygous. (B)</p> Signup and view all the answers

    In a genetic cross of Pp x Pp, what would be the expected phenotypic ratio of purple to white flowers?

    <p>3 purple : 1 white (A)</p> Signup and view all the answers

    Flashcards

    Chargaff’s Rule

    In DNA, A=T and G=C; percentages equal.

    Start Codon

    AUG codon that begins protein translation.

    Stop Codon

    Codons that end the process of translation.

    Mutagens

    Agents causing mutations, can be chemical or physical.

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    Effects of Mutations

    Mutations can be harmful, helpful, or neutral; source of variability.

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    Meiosis

    Two rounds of cell division producing 4 haploid daughter cells.

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    Haploid

    A cell with half the number of chromosomes than diploid.

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    Prophase 1

    Stage in meiosis where homologous pairs join and crossing-over occurs.

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    Crossing-over

    Exchange of genetic material between homologous chromosomes during prophase 1.

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    Structure of DNA

    DNA is made of nucleotides consisting of a phosphate, sugar, and nitrogenous base.

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    Hydrogen Bonds in DNA

    Weak bonds forming between complementary nitrogenous base pairs in DNA.

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    DNA Replication

    Process during the S phase where DNA strands separate and complementary strands are synthesized.

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    Helicase

    Enzyme that unzips the DNA molecule by breaking hydrogen bonds during replication.

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    Genotype

    The genetic makeup of an organism, represented by alleles (e.g., PP, Pp, pp).

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    Phenotype

    The observable traits of an organism (e.g., purple or white flowers).

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    Homozygous

    An organism with two identical alleles for a gene (e.g., GG or gg).

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    Heterozygous

    An organism with two different alleles for a gene (e.g., Gg).

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    Punnett Square

    A grid used to predict the genotypes and phenotypes of offspring from a genetic cross.

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    Principle of Dominance

    The concept that dominant alleles mask the effect of recessive alleles in a heterozygous genotype.

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    Crossing Plants

    When two plants breed, each contributes one allele to the offspring; e.g., PP x pp = Pp.

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    Offspring Traits

    Traits may appear in offspring that were not evident in the parents if genotypes are heterozygous.

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    Genes

    Factors passed from parents to offspring that determine traits.

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    Alleles

    Different forms of a gene that produce variations in traits.

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    Independent Assortment

    Principle stating genes for different traits can segregate independently during gamete formation.

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    P Generation

    The true breeding plants crossed to produce the F1 generation in Mendel's experiments.

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    Study Notes

    Part 1 - Chapters 12-14 Test Review

    • Pay close attention to the text in blue.
    • Red, green, and black text are supporting material.

    Genotype and Phenotype

    • Genotype: genetic makeup (genes represented by letters, e.g., PP, Pp, pp)
    • Phenotype: observable traits (e.g., purple or white flowers)

    Parental Generation (P)

    • When a purple flower (PP) is crossed with a white flower (pp), each parent contributes one allele to the offspring.
    • PP x pp = Pp (resulting in purple flowers)

    Homozygous and Heterozygous

    • Homozygous: organisms with two identical alleles (e.g., PP or pp)
    • Heterozygous: organisms with two different alleles (e.g., Pp)
    • The term "same" refers to homozygotes, while "hybrid" refers to heterozygotes

    Punnett Square

    • Used to predict the outcome of a cross.
    • One parent's genotype is placed across top and the other on side.
    • Example: RR (round) x rr (wrinkled) peas will produce all round offspring (Rr)

    Probability and Heredity

    • Not all organisms with the same characteristics have the same alleles.
    • GG and Gg result in green pods.
    • Organisms with identical alleles (homozygous): GG or gg.
    • Organisms with different alleles (heterozygous): Gg

    Mendel's Experiments

    • Studied inheritance in garden peas.
    • Crossed true-breeding plants.
    • Controlled variables by studying one or two traits at a time.
    • Dominant alleles are expressed over recessive alleles.

    Principle of Dominance

    • Organisms with both dominant and recessive alleles for a trait will exhibit the dominant characteristic.

    Punnett Squares (Example)

    • Parent Genotype (Pp): 25% white and 75% purple offspring.
    • Both parents are heterozygous for the color trait.

    Genes and Alleles

    • Genes: factors passed from parents to offspring.
    • Alleles: different forms of a gene.
    • Mendel crossed true-breeding plants with different traits (P generation).

    Independent Assortment

    • Genes for different traits can be segregated independently during gamete (sex cell) formation.
    • Mendel's results were close to a 9:3:3:1 ratio.

    Chromosome Number

    • Homologous chromosomes: matching pairs of chromosomes (one from each parent).
    • Diploid (2n): Cells with two sets of homologous chromosomes.
    • Haploid (n): Cells with one set of chromosomes.

    Meiosis

    • Process that reduces the number of chromosomes per cell in half through separation of homologous chromosomes in a diploid cell.
    • Involves two distinct divisions (Meiosis I & Meiosis II).
    • Produces four haploid cells.

    Comparing Meiosis & Mitosis

    • Mitosis: single division resulting in two identical diploid daughter cells.
    • Meiosis: two divisions resulting in four different haploid daughter cells.

    Prophase 1 of Meiosis

    • Homologous pairs join: chromosomes crossover (sections switch places): increases variation in gametes.

    DNA Structure

    • Made of nucleotides, including phosphate, deoxyribose sugar, and a nitrogenous base.
    • Nitrogenous bases: A, T, G, C.

    The Double Helix Model

    • Hydrogen bonds between nitrogenous bases (A-T and G-C).

    Copying the Code (Replication)

    • During DNA replication, two new complementary strands are synthesized using the original strand's base-pairing rules.
    • Example: original strand: TACGTTGCCT, new strand: ATGCAACGGA.

    Replication Process (Details)

    • Enzymes unzip the DNA molecule by breaking hydrogen bonds between base pairs.
    • Helicase is the "unzipping enzyme".
    • Replication starts at a single point and proceeds in two directions.
    • Each strand serves as a template to build a complementary strand.

    Chargaff's Rule

    • The percentages of adenine (A) and thymine (T) are equal, as are guanine (G) and cytosine (C) in DNA samples.

    The Genetic Code

    • Codons (three-base sequences) code for amino acids.
    • Use a genetic code chart to translate codons into amino acids.

    Mutations

    • Errors during genetic processes can cause mutations.
    • Mutagens: chemical or physical agents in the environment.
    • Examples: certain pesticides, alkaloids, tobacco smoke, UV light, x-rays.
    • Most mutations are neutral or have little or no effect.

    Effects of Mutations

    • Some mutations are harmful by dramatically changing protein structure or activity.
    • Some mutations are helpful, creating beneficial variations.

    Designing Controlled Experiments

    • Variables: changeable factors in the experiment.
    • Independent variable: is changed by the researcher.
    • Dependent variable: observed variable that's influenced by the independent variable.
    • Control groups: serve as a baseline to compare the experimental groups.

    Bacterial Transformation Experiment

    • Demonstrates that bacteria can change their genetic traits through the process of transformation as part of genetics study and experimentation.

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    Chapters 12-14 Genetics Review PDF

    Description

    This quiz covers key concepts from chapters 12 to 14 of genetic studies, focusing on genotype, phenotype, homozygous and heterozygous traits, and the use of Punnett squares for predicting genetic outcomes. Refresh your understanding of heredity and genetic probability as you prepare for the test.

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