summary

• What is the genetic constitution of an organism called?

  Genotype
• How is phenotype defined?

  Expression of genotype and environmental interaction
• What are alleles?

  Variations of a particular gene
• How do alleles arise?

  By mutation in DNA base sequence
• How many alleles of a gene can diploid organisms have?

  2 alleles
• What is the significance of homologous pairs in diploid organisms?

  They have 2 sets of chromosomes
• What is a dominant allele?

  Always expressed in the phenotype
• When is a recessive allele expressed?

  When two copies are present
• What are codominant alleles?

  Both alleles contribute to the phenotype
• What does homozygous mean?

  Alleles at a locus are the same
• What does heterozygous mean?

  Alleles at a locus are different
• What do monohybrid and dihybrid crosses show?

  • Monohybrid cross: inheritance of one characteristic
  • Dihybrid cross: inheritance of two characteristics
• What is the expected phenotype ratio from a monohybrid cross between a non-grey female and a heterozygous grey male?

  1:1 ratio of grey to non-grey
• What is the dominant allele for shell colour in the snail species described?

  Brown allele (Cᴮ)
• What is the result of a cross between two pink-shelled snails?

  Produces pink-shelled and yellow-shelled snails
• What are the possible offspring genotypes from the pink-shelled snail cross?

  CᴿCᴿ, CᴿCᵂ, CᵂCᵂ
• What are the possible phenotypes from the ABO blood group inheritance?

  AB, A, B, O blood groups
• What is the probability of a child having blood group O from two heterozygous parents?

  1 in 4 chance
• How can you determine if an allele is dominant using a pedigree diagram?

  Parents with the phenotype have an affected child
• How can you determine if an allele is recessive using a pedigree diagram?

  Parents without the phenotype have an affected child
• What is independent segregation in dihybrid crosses?

  • Alleles from one gene pair segregate independently of another
  • Results in various combinations of alleles in gametes
• What is the expected phenotype ratio from a dihybrid cross?

  1:1:1:1 ratio
• What is a sex-linked gene?

  A gene located on a sex chromosome
• Why are males more likely to express a recessive X-linked allele?

  They have only one X chromosome
• What is the probability of a hairless calf from a hair-carrying male and female?

  25% chance
• What is the phenotype of a tortoiseshell female cat?

  Patchy fur of both ginger and black
• What is the expected phenotype ratio from a tortoiseshell female crossed with a black male?

  1:1:1:1 ratio
• What are the expected offspring phenotypes from a dihybrid cross with sex linkage?

  • Grey body, red eyes
  • Grey body, white eyes
  • Black body, red eyes
  • Black body, white eyes
• What are the parental phenotypes in the tortoiseshell and black male cross?

  Tortoiseshell female and black male
• What are the parental genotypes in the tortoiseshell and black male cross?

  XᴳXᴮ and XᴮY
• What are the gamete genotypes produced by the tortoiseshell female?

  Xᴳ and Xᴮ
• What are the gamete genotypes produced by the black male?

  Xᴮ and Y
• What are the offspring genotypes from the tortoiseshell and black male cross?

  • XᴳXᴮ
  • XᴮXᴮ
  • XᴳY
  • XᴮY
• What are the offspring phenotypes from the tortoiseshell and black male cross?

  • Tortoiseshell female
  • Black female
  • Ginger male
  • Black male
• What is the expected ratio of phenotypes in the offspring of the tortoiseshell and black male cross?

  1:1:1:1
• What are the parental phenotypes in the fruit fly cross?

  Grey-bodied, white-eyed female and black-bodied, red-eyed male
• What are the parental genotypes in the fruit fly cross?

  GgXʳXʳ and ggXᴿY
• What are the gamete genotypes produced by the grey-bodied, white-eyed female fly?

  GgXʳ and gXʳ
• What are the gamete genotypes produced by the black-bodied, red-eyed male fly?

  gXᴿ and gY
• What are the offspring genotypes from the fruit fly cross?

  • GgXᴿXʳ
  • GgXʳY
  • ggXᴿXʳ
  • ggXʳY