# Worksheet: Genetic Diagrams

In this worksheet, we will practice using genetic diagrams to make predictions about genotypes and phenotypes.

**Q1: **

A heterozygous black cat (Bb) reproduces with a homozygous recessive brown cat (bb).

Which Punnett square shows the correct cross?

- A
B b B BB Bb b Bb bb - B
B b b Bb Bb b bb bb - C
B b b Bb bb b Bb bb - D
B B b Bb Bb b Bb Bb

**Q2: **

Sex in humans is determined by two chromosomes, X and Y. What is the correct combination of chromosomes for males and females from the given choices?

- AXX = male, XY = female
- BXY = male, XX = female

**Q3: **

Which of the following Punnett squares correctly outlines how sex is determined in humans?

- A
Gametes X X X XX XY X XX XY - B
Gametes X Y X X Y X X Y - C
Gametes X Y X XX XX X XY XY - D
Gametes X Y X XX XY X XX XY

**Q4: **

The allele for orange fur in tigers is dominant (T).

What is the genotype of a tiger homozygous dominant for orange fur?

- ATt
- BTT
- Ctt

What is the genotype of a tiger heterozygous for orange fur?

- Att
- BTt
- CTT

What is the probability that a homozygous dominant male and a heterozygous female will produce offspring with orange fur?

**Q5: **

The allele for freckles in humans is dominant (F). What is the probability that a couple who are both heterozygous for the allele will have a child with freckles? Use a Punnett square to help you.

**Q6: **

What is the probability that a pregnancy will produce a female offspring?

**Q7: **

A plant homozygous dominant for red flowers (RR) reproduces with a plant homozygous recessive for white flowers (rr).

Which Punnett square shows the correct cross?

- A
R R R RR RR r Rr Rr - B
R R r Rr RR r Rr RR - C
R R r Rr Rr r Rr Rr - D
r r r Rr Rr r Rr Rr

What percentage of the offspring will have white flowers?

**Q8: **

Give the correct combination of alleles to complete the Punnett square provided.

G | G | |
---|---|---|

1 | GG | GG |

2 | Gg | Gg |

- A1 = g, 2 = G
- B1 = G, 2 = G
- C1 = G, 2 = g
- D1 = g, 2 = g

**Q9: **

The allele for having a straight hairline (h) is recessive to the allele for having a widow’s peak (H). A couple, both heterozygous for this trait, are having a child.

What is the probability that the child will have a straight hairline?

What is the probability that the child will be a carrier for the straight hairline allele?

What is the probability that the child will be homozygous dominant?

**Q10: **

Give the correct combination of alleles to complete the Punnett square provided.

A | 2 | |
---|---|---|

1 | AA | Aa |

a | Aa | aa |

- A1 = a, 2 = A
- B1 = A, 2 = a
- C1 = a, 2 = a
- D1 = A, 2 = A