NAME: CHAPTER 4 HANDOUT BLM 4-4 Punnett Square Worksheet 5. A cross between a ta
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NAME: CHAPTER 4 HANDOUT BLM 4-4 Punnett Square Worksheet 5. A cross between a tall pea plant and a short pea plant produces offspring of which roughly half are tall and half are short. What are the genotypes of the parental plants? Support your square. Which of the parental genotypes is true breeding? Genotype a : a) .True breed.nc ? 6. As sume that, in humans, the allele for brown eyes (B) is dominant to the allele for blue eyes (b). a) What is the probability that the first child of two heterozy gous brown-eyed parents will be blue- eyed? Support your answer with a Punnett square. / dhonce thot a child will have ue 66 B eyes i both parents are he-terozygg brown-eyed parents Biology 11C Blackline Master BLM 4-4 Punnett Souare Worksheet 0 2013 McGraw-Hill Ryerson Limited 978-1-25-902291-3Explanation / Answer
6 b) The answer is 1/4. The probability for a child to carry certain traits doesnt is independent of the trait of the first child. The second child's traits will depend solely upon the traits of the parents. In the second pregnancy the chances for a child with blue eyes will be as same as they were in the first pregnancy.
7. a)Allele for round seeds (R) is dominant over the allele for wrinkled seeds (r). For the round phenotypes there can be two genotypes- RR (homozygous dominant) or Rr (heterozygous dominant) whereas for the wrinkled seeds there is only one genotype - rr(homozygous recessive). Therefore, just by inspection of the wrinkled seed phenotype you can say for sure that the genotype that they carry is rr.
b and c) In a test cross, the individual of unkown phenotype is crossed with the individual whos phenotype and genotype are not only known but are homozzygous recessive. The individual whose genotype you cannot determine just by inspection is either homozygous dominant or heterozygous dominant.
lets see the cross between RR x rr and Rr x rr
Thus if from a test cross, only dominant phenotype is produced then the genotype of the unknown individual is homozygous dominant i..e RR. This is simply because the two bure breeding lines always produce heterozygotes.
From here we can see that if from a test cross both phenotypes are produced in 1:1 ratio, then the genotype of the unkown individual is heterozygous dominant i.e. Rr
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