Punnett Square Practice
A Grade 9 science worksheet on Punnett Squares, including monohybrid crosses, genotypes, and phenotypes.
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Punnett Square Practice
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Read each question carefully and use a Punnett square to determine the probabilities of genotypes and phenotypes. Show all your work.
1. In pea plants, tall (T) is dominant over short (t). Cross a heterozygous tall plant with a short plant.
a) What are the genotypes of the parent plants?
b) What are the possible genotypes of the offspring and their ratios?
c) What are the possible phenotypes of the offspring and their ratios?
2. In guinea pigs, rough coat (R) is dominant over smooth coat (r). A homozygous rough-coated guinea pig is crossed with a smooth-coated guinea pig.
The genotype of the homozygous rough-coated parent is .
The genotype of the smooth-coated parent is .
All offspring will have a genotype of and a phenotype of .
3. If two heterozygous tall pea plants (Tt) are crossed, what percentage of the offspring are expected to be short (tt)?
0%
25%
50%
75%
4. A Punnett square is used to predict the actual outcome of a genetic cross, not just the probabilities.
True
False
5. In cats, black fur (B) is dominant over white fur (b). If a heterozygous black cat mates with a homozygous white cat, what is the probability that their kittens will have black fur?