Inheritance, Variation & Evolution

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Cards (69)

  • Give 2 examples of inherited disorders?
    • Polydactyly (homozygous dominant allele)
    • Cystic fibrosis (homozygous recessive allele)
  • What is inherited disorder?

    Disorder that is caused by the inheritance of certain alleles
  • What are alleles?

    Different forms of gene
  • What is genotype?

    The alleles
  • What is phenotype?

    Physical characteristics
  • What is homozygous?

    Both alleles of an organism are the same
  • What is heterozygous?

    The alleles of an organism are different
  • Some characteristics are controlled by a single gene.
    • Fur colour in mice
    • Red-green colour blindness in humans
  • A dominant allele is always expressed, even if only one copy is present (75%)
  • A recessive allele is only expressed if two (both) copies are present (no dominant ,25%)
  • Most characteristics are a result of multiple genes interacting, rather than a single gene
  • What the name of the diagram to determine the expected percentages of different genotypes in the offspring of two parents?
    Punnett square
  • How many chromosomes do ordinary human body cells contain?
    46 (23 pairs)
  • 22 pairs of chromosomes control characteristics only but one of the pairs carries the genes that determine sex
    • Female: XX (same chromosome)
    • Male: XY (different chromosome)
  • What is variation?

    The difference in the characteristics of individuals in a population
  • What cause variation in individuals?
    • The genes they have inherited (genetic causes)
    • The conditions in which they have developed (environmental causes)
    • A combination of genes and the environment
    • —>There is usually extensive genetic variation within a population of a species
  • All variants arise from mutations, which
    • most have no effect on the phenotype
    • some influence phenotype
    • very few determine phenotype
  • Mutations occur continuously in the genome, but very rarely a mutation will lead to a new phenotype
  • If the new phenotype is suited to an environmental change, it can lead to a relatively rapid change in the species