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Explain mendelives monohybrid theory |
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Answer» Monohybrid Cross\xa0-\xa0A cross which involves only a single pair of contrasting characters.\tConsider pea plants with a pair of contrasting characters—tallness and dwarfness—with respect to the height of the stem. Because pea plants are self-fertilising, Mendel bred them for several generations till he obtained pure varieties. The parental generation P1\xa0has the genotype TT for a pure tall parent plant and tt for a pure dwarf plant. The two parents are homozygous with one type of gamete each, i.e. T from tall parent and t from dwarf parent. These two plants are crossed with one another.\tMendel found that all plants were tall. He called them first filial or F1\xa0generation seeds. The F1\xa0generation has genetic constitution Tt. It is genotypically a hybrid and a heterozygous plant with two different alleles. Phenotypically, the plant is tall because the allele or the gene T for tallness masks the effect of its corresponding recessive gene t.\tF1\xa0plants are self-pollinated to obtain the F2\xa0generation.\tThe second filial generation F2\xa0has a genotypic ratio of 1 TT:2 Tt:1 tt. In this case, because the allele T for tallness is dominant, the pea plants with genotype Tt will be tall. The phenotypic ratio is 3 tall:1 dwarf. Genotypically, it shows 3 types of plants: 1 TT, which is homozygous tall, 2 Tt which are heterozygous tall and 1 tt which is homozygous dwarf. Thus, the genotypic ratio is 1 TT:2 Tt:1 tt. I hope this is helpful to you ?? A monohybrid cross is a genetic mix between two individuals who have homozygous genotypes, or genotypes that have completely dominant or completely recessive alleles, which result in opposite phenotypes for a certain genetic trait.... |
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