William Bateson and Reginald Punnett were not able to detect genetic linkage in sweet peas. Which of the following explains why Thomas Morga genetic linkage? He crossed two heterozygous individuals and was able to determine offspring genotypes from their phenotypes. He performed a three-point test cross. He crossed a heterozygous individual with a homozygous recessive individual and was able to determine progeny genotypes from their pheno He sequenced the DNA and was able to determine the distance between the genes. He performed Lod score analysis to determine the distance between the genes he was studying.
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The question asks why Thomas Morgan was able to detect genetic linkage, while Bateson and Punnett were not, given the options provided. This requires knowledge of the historical context of genetics and the methods used by these scientists. Show more…
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Problem 3 Even before Morgan's fruit fly work, Bateson and Punnett found evidence of genetic linkage in the sweet pea, but they didn't understand it fully. They crossed pure-breeding plants exhibiting purple flowers (P) and long pollen grains (L) with pure-breeding plants exhibiting red flowers (p) and round pollen grains (l) to produce the F1 generation, all with purple flowers and long pollen grains. Next, they crossed F1 x F1 to produce the F2 generation. A. (4 points) Assuming Mendel's law of independent assortment (no genetic linkage), each diploid F1 parent can contribute 4 possible pairs of alleles. Write down these pairs. B. (4 points) Assuming Mendel's law of independent assortment (no genetic linkage), what is the expected distribution of phenotypes in the F2 generation? purple and long: purple and round: red and long: red and round: When Bateson and Punnett performed the F2 cross, they counted the following phenotypes: purple and long: 4831 (69.5%) purple and round: 390 (5.6%) red and long: 393 (5.7%) red and round: 1338 (19.2%) Total Progeny: 6952 C. (2 points) Is Bateson and Punnett's data consistent with independent assortment? (Y or N) D. (4 points) Assuming genetic linkage between the genes controlling flower color and pollen grain shape, each F1 parent can contribute 2 possible allele pairs if there is no recombination, and 2 alternative pairs if there is recombination. Write down these pairs. Without recombination: With recombination: The F1 plants are crossed with red and round plants, producing the following phenotypes: purple and long: 2405 (43.8%) purple and round: 325 (5.9%) red and long: 337 (6.1%) red and round: 2420 (44.1%) Total Progeny: 5487 E. (2 points) What is the recombination rate between the genes controlling flower color and pollen grain shape?
Adi S.
1. What would you expect to have happened if Mendel had worked with only partially linked genes? 3. If two loci show a 50% recombination frequency in a two-point test cross, what could happen? 2. Which of the following is best to test linkage between two loci? A. monohybrid cross. B. dihybrid cross. C. cross with at least 3 loci.
Studies like the one described in question AP12.1 were carried out by Morgan and Sturtevant beginning in 1911. The discovery of linkage was made by Bateson and Punnett in 1900. They crossed a true-breeding purple (P) plant with long seeds (L) with a true-breeding red (r) plant with round seeds (l). They then performed a self-cross between the $\mathrm{F}_{1}$ generations. They obtained the $\mathrm{F}_{2}$ data shown below. A. Use the symbols $\mathrm{P}, \mathrm{p}, \mathrm{L},$ and 1 to construct a representation of the $\mathrm{F}_{2}$ genotypes and complete the second column in the table. B. Complete the fourth column of the table above by recording the values of the predicted numbers of plants with each genotype. C. Apply a c' test at the 95$\%$ confidence level to evaluate the claim that these data confirm linkage. The definition of the statistic $\chi^{2}=\sum \frac{(o-e)^{2}}{e}$ and this table are provided in the AP Biology Exam. D. At first, Bateson and Punnett did not see that these genes are located on the same chromosome and proceeded to measure the linkage distance between them, taking the first step toward creating a gene map. Justify the selection of data and the procedure from which data could be collected that would have provided the necessary evidence to confirm linkage and recombination.
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