Genetic diagrams

• What controls the characteristics you develop?

  The genes you inherit
• What are some examples of characteristics controlled by a single gene?


  Mouse fur colour and red-green colour blindness in humans
• How do most characteristics differ from those controlled by a single gene?


  Most characteristics are controlled by several genes interacting
• What are different versions of genes called?

  Alleles
• How many versions of every gene do you have in your body?


  Two versions (alleles) of every gene
• What does it mean if an organism is homozygous for a trait?


  It has two identical alleles for that trait
• What does it mean if an organism is heterozygous for a trait?


  It has two different alleles for that trait
• What is the dominant allele represented by in genetic diagrams?


  A capital letter
• What is the recessive allele represented by in genetic diagrams?


  A lowercase letter
• What must be true for an organism to display a recessive characteristic?


  Both alleles must be recessive
• What is the genotype of an organism?


  The combination of alleles it has
• What is the phenotype of an organism?


  The observable characteristics determined by its genotype
• What are the key terms related to genetic diagrams that you should understand?

  • Genes
  • Alleles
  • Homozygous
  • Heterozygous
  • Dominant
  • Recessive
  • Genotype
  • Phenotype
• In a genetic cross, what is the genotype of a homozygous normal hamster?


  BB
• What is the phenotype of a hamster with the genotype 'Bb'?


  Normal hearing
• What is the offspring's phenotype when a homozygous normal hamster (BB) is crossed with a superpowered hamster (bb)?


  All offspring are normal hearing
• What is the ratio of normal to superpowered offspring when two 'Bb' hamsters breed?


  1. 1
• What is the expected ratio of offspring when a homozygous dominant hamster (BB) is crossed with a homozygous recessive hamster (bb)?


  All offspring are normal
• What is the expected outcome when a homozygous dominant hamster (BB) is crossed with a heterozygous hamster (Bb)?

  All offspring are normal
• What is the dominant allele for long hair in cats?

  H
• What is the recessive allele for short hair in cats?


  h
• What is the expected ratio of offspring when a heterozygous cat (Hh) is crossed with a homozygous recessive cat (hh)?


  1. 1 ratio of long-haired to short-haired cats
• What is cystic fibrosis?


  A disorder producing thick mucus
• What does it mean if a person is a carrier for cystic fibrosis?


  They carry the allele but do not have the disorder
• What is the probability that a new baby will have cystic fibrosis if both parents are carriers?


  25%
• What is the probability that a new baby will be a carrier of cystic fibrosis if both parents are carriers?


  50%
• In a genetic cross, what is the genotype of a heterozygous pea plant?


  Rr
• What is the expected ratio of round peas to wrinkly peas when a heterozygous pea plant is crossed with a homozygous recessive pea plant?


  1. 1 ratio
• What are the steps to interpret a family tree regarding genetic disorders?


  • Identify affected individuals
  • Determine if the disorder is dominant or recessive
  • Calculate probabilities for offspring based on parental genotypes