In the tomato, red fruit (R) is dominant over yellow fruit (), and yellow flower
ID: 282304 • Letter: I
Question
In the tomato, red fruit (R) is dominant over yellow fruit (), and yellow flowers (F) are dominant over white flowers () A cross was made between true-breeding plants with red fruit and yellow flowers, and plants with yellow fruit and white flowers. All Fi offspring are heterozygotes for both traits. The Fi female plants were then test crossed to males with yellow fruit and white flowers (homozygous recessive for both traits). The following results were obtained: 333 red fruit, yellow flowers 64 red fruit, white flowers 58 yellow fruit, yellow flowers 345 yellow fruit, white flowers Total of 800 1. What are the phenotypes of the recombinant offspring of the F2 ganeration 2. The recombinant offspring of the F2 generation result of crossing over. When do you think that crossing over has occurred? Is it during male gamete formation or female gamete formation? Explain why? (Hint what are the genotypes of the Fi female and male plants) in the above cross were produced as a 3. Conduct a Chi square analysis to see if the two genes are linked (Check a solved problem S1, page 148 in the first edition text book, and page 150 in the second edition problem #1 for an idea) follow the same steps) a. Propose a hypothesis to be tested b. Find the expected (predicted) number of offspring (Hint what is the ratio of test cross results?)Explanation / Answer
1) The phenotypes of the recombinant offsprings in the F2 generation are red fruit, yellow flowers and yellow fruit, yellow flowers.
2) The crossing over occurs during the gamete formation in both males and females. This is because recombinant offsprings have the traits if both male and female parents.
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