Genetics Overview Quiz
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Questions and Answers

What is the primary structure that stores genetic information in organisms?

  • Histones
  • Chromosomes (correct)
  • Nucleosomes
  • RNA

    • Which statement accurately defines an allele?

  • Different forms of a gene that occupy the same locus on homologous chromosomes. (correct)
  • The observable characteristics expressed by an organism.
  • A pair of chromosomes that are identical in structure and gene content.
  • A unit of heredity that encodes a single protein.

    • What term is used to describe an organism that has two identical alleles for a particular trait?

  • Heterozygous
  • Dominant
  • Phenotype
  • Homozygous (correct)

    • Which of the following best describes a phenotype?

    <p>Observable characteristics resulting from gene interaction and environment.</p> Signup and view all the answers

    What is the role of histones in relation to DNA?

    <p>They package and condense DNA into chromosomes.</p> Signup and view all the answers

    In genetic terms, what does the term 'locus' refer to?

    <p>A specific position on a chromosome where a gene is located.</p> Signup and view all the answers

    What type of chromosomes contain genes that occur in pairs?

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

    If an organism has genotypes 'AA' and 'aa', what is the phenotypic outcome assuming 'A' is dominant over 'a'?

    <p>Some offspring will express the dominant trait.</p> Signup and view all the answers

    How many genes have been associated with human eye color?

    <p>15</p> Signup and view all the answers

    What is the term for the principle that states one allele can mask another?

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

    What type of mutation occurs when it happens spontaneously and can be inherited?

    <p>Hereditary mutation</p> Signup and view all the answers

    Which genetic condition is caused by a defective allele of a single gene located on chromosome 7?

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

    What is the karyotype used for?

    <p>To visualize individual chromosomes and identify abnormalities</p> Signup and view all the answers

    What is aneuploidy?

    <p>A chromosomal condition with abnormal numbers of chromosomes</p> Signup and view all the answers

    What results from a cell having one additional chromosome (2n+1)?

    <p>Trisomic condition</p> Signup and view all the answers

    Which syndrome results from the chromosomal combination XXY?

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

    Which of the following does NOT describe a feature of cystic fibrosis?

    <p>Results from a dominant allele</p> Signup and view all the answers

    What are mutagens?

    <p>Factors that increase the rate of mutations</p> Signup and view all the answers

    Study Notes

    Genetics Overview

    • Genetics is the study of heredity and variation in organisms.
    • Inheritance is the transmission of genetic information across generations.
    • Genetic information is stored in DNA within the cell nucleus and mitochondria.

    DNA, Chromosomes, and Genes

    • DNA is a double helix, formed by nucleotides (sugar, phosphate, and base).
    • Strands are connected by hydrogen bonds between complementary bases.
    • Chromosomes are compacted DNA and proteins (histones).
    • Nucleosomes coil to form chromatin, which further condenses into visible chromosomes during cell division.
    • A gene is a DNA segment encoding a single protein.
    • Genes reside at specific positions (loci) on chromosomes.
    • Offspring inherit genes from parents via chromosomes passed in reproductive cells (gametes).
    • A genome is the full set of genes in an organism.

    Key Genetic Terms

    • Homologous Chromosomes: Chromosome pairs with similar genes, leading to new combinations in sexual reproduction.
    • Alleles: Alternate forms of a gene that occupy the same locus on homologous chromosomes, affecting the same trait.
      • Most multicellular organisms are diploid (two alleles per gene).
      • Homozygous: Identical alleles for a trait.
      • Heterozygous: Different alleles for a trait.
    • Genotype: The genetic makeup (AA, Aa, aa).
      • Dominant alleles are represented using capital letters.
      • Recessive alleles are represented by lowercase letters.
    • Phenotype: Observable characteristics resulting from gene interaction, environment, and chance.

    Multiple Alleles

    • Multiple alleles (e.g., eye color) give variations within a species.
    • Blood type (ABO) is controlled by multiple alleles (IA, IB, IO).
    • 15 genes are associated with human eye color.

    Mendel's Principles

    • Principle of Dominance: One allele masks another in the F1 generation.
    • Principle of Segregation: Gene pairs separate during gamete formation, each gamete receiving only one allele.

    Mutations

    • Mutations are random, inheritable changes in a genome's sequence.
    • Can alter phenotypes. Some are neutral (no phenotypic change).
    • Mutation rates: Vary depending on the organism and location in the genome.
    • Mutagens: Increase mutation rates (induced mutations).
    • Hereditary mutations: Occur in germ cells and are passed to all offspring's cells. Examples include cystic fibrosis, haemophilia, and sickle cell disease.
    • Cystic Fibrosis (CF): Caused by a recessive mutant gene affecting ion transport in tissues.
      • It's an autosomal recessive disease.
      • CFTR gene is on chromosome 7.
      • Affects chloride and thiocyanate transport.
      • Mucus accumulation in lungs & digestive system causes complications.
      • Couples being carriers of CF
      • 1 in 4 children will have it

    Karyotype

    • A karyotype is an organized display of an organism's chromosomes.
    • Used to identify abnormal chromosome numbers or structures.

    Alterations of the Karyotype

    • Errors in chromosome distribution during cell division can lead to:
      • Polyploidy: Multiple sets of chromosomes.
      • Aneuploidy: Abnormal number of chromosomes.
        • Trisomy (2n+1): An extra chromosome. Example: Down Syndrome (Trisomy 21).
        • Monosomy (2n-1): Missing a chromosome.
        • Nullisomy (2n-2): Missing both homologous chromosomes.
    • Aneuploidy impacts chromosome balance and can cause dysfunction or lethality in humans.

    Impact of Aneuploidy

    • Aneuploidy is a significant chromosomal change.
    • Trisomies lead to three copies of a chromosome.
    • Monosomies lead to one copy
    • Viable trisomies are possible in certain organisms, though not all trisomies are present or viable
    • Klinefelter Syndrome (XXY) illustrates a sex chromosome trisomy.
    • Down Syndrome (Trisomy 21) is a common viable human aneuploid.

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    Description

    Test your knowledge on the fundamental concepts of genetics, including DNA structure, inheritance, and genetic terminology. This quiz covers essential topics such as chromosomes, genes, and genetic variation in organisms.

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