Review of Terminology

1
Review of Terminology

• phenotype
• genotype
• homozygous
• pure line
• heterozygous
• hybrid
• dominant
• recessive

2
Terminology, continued

• P
• F1
• F2
• Testcross
• Backcross

3
Practice Questions

• 2.12. Several black guinea pigs of the same
  genotype were mated and produced 29 black and 9
  white offspring. What would you predict the
  genotypes of the parents to be?

4
?
This is an easy one.

• 2.13. If a black female guinea pig is testcrossed
  and produces at least one white offspring,
  determine (a) the genotype and phenotype of the
  sire (male parent) that produced the white
  offspring, (b) the genotype of this female.

5

• 2.14. Heterozygous black (Bb) guinea pigs are
  mated to homozygous recessive (bb) whites.
  Predict the genotypic and phenotypic ratios
  expected from backcrossing the black F1 progeny
  to (a) the black parent, (b) to white parent.

6

• 2.17. Short hair is due to a dominant gene L in
  rabbits, and long hair to its recessive allele l.
  A cross between a short-haired female and a
  long-haired male produced a litter of 1
  long-haired and 7 short-haired bunnies. (a) What
  are the genotypes of the parents? (b) What
  phenotypic ratio was expected in the offspring
  generation? (c) How many of the 8 bunnies were
  expected to be long-haired?

7

• 2.19. Black wool of sheep is due to a recessive
  allele b and white wool to its dominant allele B.
  A white buck (male) is crossed to a white ewe
  (female), both animals carry the allele for
  black. They produce a white buck lamb that is
  then backcrossed to the female parent. What is
  the probability of a backcross offspring being
  black?

8

• 2.22. Consider a cross between two heterozygous
  black guinea pigs (Bb). In how many ways can 3
  black and 2 white offspring be produced? (b) What
  is the probability from such a cross of 3 black
  and 2 white offspring appearing in any order?