Cards (16)

  • Define genotype?
    The genetic constitution of an organism
  • Define phenotype?
    Expression of an organisms genotype, and its interaction with the environment
  • What is an allele?
    Different versions of a gene found at the same locus on a chromosome
  • How many alleles per gene do diploid organisms carry?
    Two.
  • What is a dominant allele?
    An allele whose characteristic will always appear in the phenotype, so only one is needed
  • What is a recessive allele?
    An allele whose characteristic only appear in the phenotype if no dominant allele is present, meaning two must be present
  • What is meant by codominant alleles?
    Two dominant alleles that both contribute to the phenotype, either by showing a blend of both characteristics, or the characteristics appearing together
  • What is meant by homozygous and heterozygous?
    • Homozygous - both alleles are dominant, or both alleles are recessive
    • Heterozygous - one allele is dominant, one is recessive
  • Define monohybrid inheritance?
    Where one phenotypic characteristic is controlled by a single gene
  • Define dihybrid inheritance?
    Where two phenotypic characteristics are determined by two different genes present on two different chromosomes at the same time
  • What is meant by sex-linkage?
    When an allele is located on one of the sex chromosomes, meaning its expression depends on the sex of the individual
  • Why are males more likely to express a recessive sex-linked allele?
    Most sex-linked alleles are located on the X chromosome. Males only get one copy of this allele, so will express this characteristic even if it's recessive. Since females have XX chromosomes this is less likely.
  • What is meant by autosomal linkage?
    When two or more genes are located on the same autosome (non-sex chromosome). The genes are unlikely to be separated by crossing over during meiosis so are often inherited together
  • What is meant by epistasis?
    When two non-linked genes interact, with one gene either masking or supressing the other
  • Define the two types of epistasis?
    • Recessive epistasis - when two homozygous recessive alleles mask expression of another allele
    • Dominant epistasis - when one dominant allele masks expression of multiple other alleles
  • How can we use a chi-squared test in relation to genetics?
    We can compare expected phenotypic characteristics with observed ratios to test our understanding of how different genes or alleles are inherited