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
    Bb
    BBBBb
    bBbbb
  • B
    Bb
    bBbBb
    bbbbb
  • C
    Bb
    bBbbb
    bBbbb
  • D
    BB
    bBbBb
    bBbBb

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
    GametesXX
    XXXXY
    XXXXY
  • B
    GametesXY
    XXY
    XXY
  • C
    GametesXY
    XXXXX
    XXYXY
  • D
    GametesXY
    XXXXY
    XXXXY

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
    RR
    RRRRR
    rRrRr
  • B
    RR
    rRrRR
    rRrRR
  • C
    RR
    rRrRr
    rRrRr
  • D
    rr
    rRrRr
    rRrRr

What percentage of the offspring will have white flowers?

Q8:

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

GG
1GGGG
2GgGg
  • 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.

A2
1AAAa
aAaaa
  • A1 = a, 2 = a
  • B1 = A, 2 = A
  • C1 = a, 2 = A
  • D1 = A, 2 = a

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