Genetic Diagrams

• What is an allele?

  A version of a gene
• What is a dominant allele?

  An allele that is always expressed
• What is a recessive allele?

  An allele expressed with two copies present
• What does homozygous mean?

  Both alleles for a trait are the same
• What does heterozygous mean?

  Alleles for a trait are different
• What is a genotype?

  An organism's combination of alleles
• What is a phenotype?

  The characteristics an organism has
• What are the two types of genetic diagrams mentioned?

  1. Punnett square for X and Y chromosome sex determination
  2. Punnett square for genetic cross of pea plants
• What do the female gametes represent in the Punnett square for sex determination?

  XX
• What do the male gametes represent in the Punnett square for sex determination?

  XY
• What is the offspring's genotype from the sex determination Punnett square?

  XX and XY
• What is the genotype of the homozygous round pea plant?

  RR
• What is the genotype of the homozygous wrinkly pea plant?

  rr
• What is the offspring's genotype from the cross between homozygous round and homozygous wrinkly pea plants?

  All Rr
• What is the ratio of male to female offspring in the sex determination Punnett square?

  1:1
• What is the phenotype of all offspring from the homozygous round and homozygous wrinkly cross?

  All have round peas
• What is the ratio of round to wrinkly offspring from the heterozygous pea plant cross?

  3:1
• What does the example of pea plants illustrate about inheritance?

  • Shows single gene inheritance
  • Similar to traits like fur color in mice
  • Related to red-green color blindness
  • Most traits result from multiple genes