Mendel`s law of dominance states that a dominant allele is expressed in a monohybrid cross and suppresses the expression of a recessive allele. However, this recessive allele for one character is not lost and remains hidden or masked in the descendants of the F1 generation and reappears in the next generation. Using a Punnett square, calculate the distribution of phenotypic traits in the first infant generation (F1) after a cross between a homozygous female and a heterozygous male for a single location. A large breeding plant (TT) is crossed with a dwarf plant (tt). The height sign is represented by `T` for grand`t` for dwarf are the alternate form as a height sign. The hybrid Fj «Tt» is large, showing that large dominates over the dwarf, while the dwarf is not expressed in F due to the phenomenon of dominance by a large factor or gene. In this heterozygous Tt has a high phenotype, which shows that T is dominant over t-allele. For example, when round seed pea (RR) plants are crossed with wrinkled seed plants (rr), all seeds of the F1 generation turned out to be round (Rr). When these round seeds were fertilized themselves, the round and wrinkled seeds appeared in the F2 generation in a ratio of 3:1.
Therefore, in the F1 generation, the dominant character (round seeds) appeared, and the recessive character (wrinkled seeds) was removed, which reappeared in the F2 generation. In this cross, we can see that in the F1 generation, only large plants were seen, no plants were dwarf. However, in the F2 generation, the F1 offspring was crossed itself, three genotypes were observed, among which hybrids showed the dominant characteristic. According to Mendel`s law of domination. The traits are controlled by two different forms of the same gene. These alternative forms of a gene are called alleles. Of the two alleles, one is dominant, while the other is recessive. The dominant allele suppresses the expression of the recessive allele. Thus, when the two alleles are present together, the dominant masks the expression of the recessive allele. However, this does not mean that the recessive allele has lost its existence.
It remains hidden in the F1 generation and reappears in the next generation. A single-hybrid cross is given below. Explain the law of dominance with a monohybrid cross. Briefly mention T.H. Morgan`s contribution to genetics. What is family tree analysis? Do you suggest how such an analysis can be useful? When two different factors (genes) or a pair of contrasting forms of a trait are present in an organism, only one is expressed in the F generation and is called dominant, while the other remains unexpressed and is called recessive factors (gene).