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Name _______________________________________ Date ______________ Period _______
Worksheet: Punnett Square Review
B I O L O G Y : C H A P T E R 6 & 7
Directions: Answer the following questions using your notes and textbook
- In pea plants, tall (T) plants are dominant over short (t) plants. Complete the following crosses and give the genotypic and phenotypic ratios of offspring.
a. TT x tt
b. Tt x tt
c. Tt x Tt
- In pea plants, purple flowers (P) are dominant over white (p) flowers. Complete the following crosses and give the genotypic and phenotypic ratios of offspring.
a. A heterozygous purple plant is crossed with a homozygous purple plant.
b. A cross between two pea plants produces offspring in which approximately 50% of the flowers are white and 50% are purple. What are the genotypes of the parents? Show punnett square to support your answer.
c. A cross between two purple pea plants yields approximately 25% of the offspring exhibiting white flowers. What are the genotypes of the parents? Show punnett square to support your answer.
- A widow’s peak in humans is determined by a dominant/recessive inheritance. A person who is purebred for widow’s peak is crossed with a person who is purebred for no widow’s peak. All of the offspring have a widow’s peak. Which trait is dominant and which is recessive? Show punnett square to support your answer.
- In guinea pigs, black fur is dominant. If a black guinea pig is crossed with a white guinea pig and the litter contains a white offspring, the genotype of the black-haired parent is probably? Show punnett square to support your answer.
- In minks, brown is dominant over silver-blue color.
a. What offspring would you predict if you crossed a homozygous brown mink with a silver-blue mink? Show punnett square to support your answer.
b. What would the genotypic and phenotypic ratios of two F2 generation mink from the above problem be if they were crossed? Show punnett square to support your answer.
b. Would it be possible to have any red cattle when two roan cattle are crossed? Show punnett square to support your answer.
- In Guinea pigs, the genotype (BB) is black, and the genotype (bb) is white color, and (Bb) is grey color, The gene (B) and (b) are sex-linked.
a. What type of offspring are to be expected in a cross between a black female and a white male?
b. A heterozygous female is crossed with a white male. What are the expected genotypic and phenotypic ratios of the offspring?
c. Would it ever be possible to produce a male with grey hair? Explain
- In humans, colorblindness is due to the reccesive allele (c), and normal vision is due to the dominant allele (C). Color blindness is a sex-linked trait.
a. What is the expected offspring between a normal man and a colorblind woman? Give both genotypic and phenotypic ratios of offspring
b. A normal male is crossed with a female who is not colorblind? Would it ever be possible to produce offspring that are colorblind? Show punnett square to support your answer.
c. What would you expect when a colorblind man marries a colorblind woman? Give both genotypic and phenotypic ratios of offspring.
d. Is it ever possible to have a male that is a carrier for colorblindness? Explain
e. Would there ever be an instance when a female could not be a carrier? Explain
- The chart below shows the inheritance of human blood types. There are four different phenotypes possible: A, B, AB, and O. The alleles A and B are codominant, and the O allele is recessive to both A and B.
a. A person with IAIB^ is crossed with a person who is IAIA. What are the genotypic and phenotypic ratios of the offspring?
