Heritability and Phenotype in Evolution
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Questions and Answers

Which type of mutation is MOST likely to be passed on and used to track the genetic relationship of taxa?

  • Deleterious mutations in expressed genes.
  • Mutations arising from replication errors that are expressed.
  • Harmful mutations removed by natural selection.
  • Mutations in junk DNA that are not expressed. (correct)

    • What is the primary consequence of nondisjunction during meiosis?

  • The duplication of an entire chromosome strand.
  • The creation of daughter cells with extra or missing chromosomes. (correct)
  • The lengthening of one chromatid arm compared to its sister.
  • The production of gametes with an equal number of chromosomes.

    • Aneuploidy refers to a condition where there is:

  • An extra or missing chromosome. (correct)
  • The deletion of a chromosomal arm in a cell division
  • An identical number of chromosomes within each diploid cell.
  • An exact multiple of the haploid chromosome number.

    • Which of the following BEST describes the cause of unequal crossing over?

    <p>Misalignment of chromatids during meiosis. (B)</p> Signup and view all the answers

    How do asexually reproducing organisms, like bacteria, primarily acquire genetic variation?

    <p>Through mutations and lateral gene transfer mechanisms. (D)</p> Signup and view all the answers

    What is the mechanism of bacterial transformation?

    <p>The uptake of DNA fragments from the surrounding environment. (C)</p> Signup and view all the answers

    Transduction in bacteria involves:

    <p>The use of viral capsids to transfer bacterial DNA. (B)</p> Signup and view all the answers

    Conjugation involves:

    <p>The direct transfer of plasmid DNA between bacteria. (B)</p> Signup and view all the answers

    What is the critical role of heritability in the context of Darwinian evolution?

    <p>It allows traits favored or disfavored by the environment to be passed to the next generation, enabling evolution. (A)</p> Signup and view all the answers

    According to the provided information, what did Darwin identify as a missing piece in his theory of natural selection?

    <p>The mechanism by which traits are inherited and how variation arises. (B)</p> Signup and view all the answers

    What is the relationship between genotype and phenotype according to the text?

    <p>Genotypes encode for phenotypes, though expression isn't always absolute. (B)</p> Signup and view all the answers

    Why is genetic variation critical for species survival?

    <p>It allows the species to quickly adapt to environmental changes and selection pressures. (A)</p> Signup and view all the answers

    What is the concept highlighted by Richard Dawkins regarding genes?

    <p>Genes strive solely for their own replication and transfer to the next generation. (A)</p> Signup and view all the answers

    Which of the following is encompassed by the term 'genome'?

    <p>All of the hereditary information, including non-gene stretches of DNA, in an individual. (B)</p> Signup and view all the answers

    What does the term 'gene pool' refer to?

    <p>The complete collection of alleles for all genes within a population. (B)</p> Signup and view all the answers

    What is the primary function of a gene on a chromosome according to the text?

    <p>To directly or indirectly cause a specific phenotype via the production of a polypeptide. (B)</p> Signup and view all the answers

    What is a locus?

    <p>The location of a gene on a chromosome. (D)</p> Signup and view all the answers

    Which term describes different versions of a gene that occur at the same locus?

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

    How can similar genotypes result in different phenotypes?

    <p>Due to environmental pressures affecting gene expression. (B)</p> Signup and view all the answers

    What is convergent evolution?

    <p>Similar traits evolving in organisms that are not closely related, but exist in similar locations. (C)</p> Signup and view all the answers

    What is the structure made of DNA and associated proteins that carries genes in eukaryotic cells?

    <p>Chromosome (C)</p> Signup and view all the answers

    What does the term 'ploidy' refer to?

    <p>The number of chromosomes in a set, and the number of sets of chromosomes in a cell. (D)</p> Signup and view all the answers

    What is the term for pairs of chromosomes, one copy from each parent?

    <p>Homologous chromosomes (C)</p> Signup and view all the answers

    What does 'diploid' (2n) mean?

    <p>Having a homologous pair of each kind of chromosome. (C)</p> Signup and view all the answers

    What is the process of producing gametes (egg and sperm) by halving the number of chromosomes?

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

    When do non-sister chromatids exchange genetic information?

    <p>During meiosis I, in the first stage. (A)</p> Signup and view all the answers

    What is a tetrad?

    <p>A set of four chromatids consisting of two sister chromatids from each parent. (B)</p> Signup and view all the answers

    How does the random alignment of tetrads in meiosis I increase genetic variation?

    <p>By determining whether the daughter cell receives all maternal, all paternal, or a mixture of homologs. (C)</p> Signup and view all the answers

    In meiosis II, what separates into the gametes?

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

    Besides meiosis, what other factor introduces variation into the puzzle of reproduction?

    <p>The selection of a mate (A)</p> Signup and view all the answers

    What can cause mutations?

    <p>Environmental mutagens like radiation and chemicals. (C)</p> Signup and view all the answers

    Study Notes

    Heritability and Phenotype

    • Heritability is crucial for Darwinian evolution. Phenotypes must be inheritable for natural selection to operate.
    • Darwin recognized the importance of heritability but lacked a mechanism for inheritance. This was discovered shortly after his work.
    • Phenotypes (measurable traits) are determined by genotypes (genes), but a precise phenotype doesn't always result from a specific genotype.
    • Genetic variation is the basis of phenotypic variations. Without this variation, there would be no selection pressure from the environment.
    • Genes are "selfish," striving for replication and transfer to the next generation; phenotypes are the tools genes use to achieve this.

    Genetic Definitions

    • Genome: All hereditary information in an organism (including non-gene parts).
    • Gene pool: All alleles (versions) of all genes in a population.
    • Genotype: All alleles within an individual (or a specific set of alleles).
    • Genes: DNA segments coding for polypeptides (traits). They can also regulate other genes.
    • Locus: A gene's location on a chromosome.
    • Alleles: Different versions of a gene at the same locus.

    Genotype vs. Phenotype

    • Similar genotypes can produce different phenotypes due to environmental influences.
    • Identical twins have slightly different phenotypes because developmental environments vary.
    • Similar phenotypes can arise from distinct genotypes; convergent evolution provides an example (gray wolf and Tasmanian wolf).
    • Exact identical phenotypes require identical genotypes and homogeneous developmental conditions (nearly impossible in organisms outside a lab).

    Variation in Eukaryotes

    • Chromosomes: DNA and associated proteins; occur in sets, each with unique chromosomes.
    • Ploidy: The number of chromosome sets in a cell (e.g., diploid [2n] has two sets).
    • Homologous chromosomes: Matching chromosome pairs (maternal and paternal) with the same genes, but potentially different alleles.
    • Haploid (1n): One set of chromosomes.
    • Diploid (2n): Two sets of chromosomes. Example: Most animals are diploid; humans are diploid. Some organisms have haploid males and diploid females, like ants, bees & wasps.
    • Dominance: One allele obscuring the effect of another in a diploid organism.
    • Meiosis: The process of gamete (egg & sperm) formation. It halves the chromosome number to produce haploid gametes.

    Variation in Meiosis

    • Meiosis involves two divisions: Meiosis I and Meiosis II; both are important for further variation
    • Crossing over: Homologous chromosomes exchange genetic material during meiosis I, creating new combinations of alleles – a key source of variation.
    • Random alignment: Homologous chromosomes randomly align during meiosis, further shuffling genetic combinations in daughter cells.

    Other Sources of Variation

    • Mutations: Changes in DNA sequences (e.g., from radiation, chemicals) important but typically not deleterious. Used to study relationships between types of organisms.
    • Nondisjunction: During meiosis, chromosomes may fail to separate properly, resulting in gametes with too many or too few chromosomes. Down syndrome is an example.

    Asexual Reproduction

    • Asexual reproduction (e.g., bacteria, budding) typically creates genetically identical offspring.
    • Three mechanisms that create variation in asexually reproducing organisms:
      • Transformation: Ingestion of external DNA by bacterial cells.
      • Transduction: Transfer of genetic material by viruses.
      • Conjugation: Transfer of genetic material between bacterial cells.

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    Description

    This quiz explores the concepts of heritability and phenotypes in the context of Darwinian evolution. Understand how genetic variation contributes to phenotypic diversity and the relationship between genotypes and measurable traits. Test your knowledge on key genetic definitions.

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