Question

98 Mendelian Genetics Exercise D: Mendel's Dihybrid Cross But wait there's morel Mender's monohybrid crosses established that inheritance of phenotypes happened by the interactions of discrete particles' (we now call alleles). Further, he discovered that those alleles segregate during the process of meiosis in the production of gametes, which recombine during fertilization. The result of these two insights can easily be predicted by a technique developed by R. C. Punnett. Once these principles were established, Mendel sought to understand how multiple phenotypes were related to each other during inheritance. He developed two alternate hypotheses Dependent assortment hypothesis The dependent assortment hypothesis predicts that phenotypes are linked to each other. For example, a purple-flowered plant would always have green seeds (but never yellow seeds). Independent assortment hypothesis Alternatively, flower color and seed color could be independently assorted, in which purple flowered plants could have green or yellow seeds, and a white-flowered plant could also have green or yellow seeds. In other words, flower color is independent of seed color. Mendel's dihybrid crosses To test these alternate hypotheses, Mendel used the same approach as he did in his monohybrid crosses, except this time he analyzed two phenotypes at the same time. For our example, we will analyze his results of flower and seed color. He began his experiment by conducting several controlled crosses of one plant with two known dominant alleles generating a pure line: homozygote purple-flowered (FF) and yellow-seeded (55). Collectively this is represented as FFSS. He conducted another controlled cross of another plant with two known recessive alleles, ffss. 14. Refer to table 1, what was the phenotype of the ffss genotype of the P generation in Mendel's dihybrid cross? and 15. From what Mendel understood about dominant and recessive phenotypes from his monohybrid crosses, he expected all of the offspring in the F, generation to have the following phenotypes: and FS 1 FS FFSS Ff5s Results of Mendel's dihybrid F, generation The results of the F, generation provided the evidence to reject one of his alternate hypotheses, while supporting the other. The dependent assortment hypothesis predicted that the allele of one gene was linked to the allele of another gene. For example, dominant alleles expressing flower color (F) would always be linked with the dominant alleles expressing seed color (S). Alternatively, recessive alleles would also link: would always be associated with s. In other words, gametes would either have the allele combination FS or fs, but never Fs or fs. Expected genotypic results supporting the dependent assortment (which wasn't supported)of the F, generation are shown in Fig. 3. fs FfSs f fs Fig. 3. Expected genotypic results F, supporting the depender assortment hypothesis.

Answer 1

98 Mendelian Genetics Exercise D: Mendel's Dihybrid Cross But wait there's morel Mender's monohybrid crosses established that inheritance of phenotypes happened by the interactions of discrete "particles (we now call alleles). Further, he discovered that those alleles segregate during the process of meiosis in the production of gametes, which recombine during fertilization. The result of these two insights can easily be predicted by a technique developed by R. C. Punnett. Once these principles were established, Mendel sought to understand how multiple phenotypes were related to each other during inheritance. He developed two alternate hypotheses: Dependent assortment hypothesis The dependent assortment hypothesis predicts that phenotypes are linked to each other. For example, a purple-flowered plant would always have green seeds (but never yellow seeds). Independent assortment hypothesis Alternatively, flower color and seed color could be independently assorted, in which purple-flowered plants could have green or yellow seeds, and a white-flowered plant could also have green or yellow seeds. In other words, flower color is independent of seed color. Mendel's dihybrid crosses To test these alternate hypotheses, Mendel used the same approach as he did in his monohybrid crosses, except this time he analyzed two phenotypes at the same time. For our example, we will analyze his results of flower and seed color. He began his experiment by conducting several controlled crosses of one plant with two known dominant alleles generating a pure line: homozygote purple-flowered (FF) and yellow-seeded (SS). Collectively this is represented as FFSS. He conducted another controlled cross of another plant with two known recessive alleles, ffss. 14. Refer to table 1, what was the phenotype of the ffss genotype of the P generation in Mendel's dihybrid cross? white flower and and green seed 15. From what Mendel understood about dominant and recessive phenotypes from his monohybrid crosses, he expected all of the offspring in the F, generation to have the following phenotypes: purple flower and yellow seed FS fs FS FFSS FfSs Results of Mendel's dihybrid Fgeneration The results of the F, generation provided the evidence to reject one of his alternate hypotheses, while supporting the other. The dependent assortment hypothesis predicted that the allele of one gene was linked to the allele of another gene. For example, dominant alleles expressing flower color (F) would always be linked with the dominant alleles expressing seed color (S). Alternatively, recessive alleles would also link: f would always be associated with s. In other words, gametes would either have the allele combination FS or fs, but never Fs or fS. Expected genotypic results supporting the dependent assortment (which wasn't supported)of the F, generation are shown in Fig. 3. fs FfSs ffss Fig. 3. Expected genotypic results F2 supporting the depender assortment hypothesis.

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