Hereditary and Variation MCQs for NEET — Botany Questions with Answers

The context states: 'Following this synthesis of ideas, experimental verification of the chromosomal theory of inheritance by Thomas Hunt Morgan and his colleagues, led to discovering the basis for the variation that sexual reproduction produced.'

The summary states: 'Mendel proposed the principles of inheritance, which are today referred to as ‘Mendel’s Laws of Inheritance’. He proposed that the ‘factors’ (later named as genes) regulating the characters are found in pairs known as alleles.'

The text mentions: 'Morgan worked with the tiny fruit flies, Drosophila melanogaster (Figure 4.10), which were found very suitable for such studies.'

The text states: 'Sutton united the knowledge of chromosomal segregation with Mendelian principles and called it the chromosomal theory of inheritance.'

The text lists several reasons for suitability but does not mention 'high blending of parental traits'. In fact, Mendel's work emphasized the lack of blending. The reasons provided are: 'They could be grown on simple synthetic medium in the laboratory. They complete their life cycle in about two weeks, and a single mating could produce a large number of progeny flies. Also, there was a clear differentiation of the sexes – the male and female flies are easily distinguishable. Also, it has many types of hereditary variations that can be seen with low power microscopes.'

The summary states: 'After knowing that the genes are located on the chromosomes, a good correlation was drawn between Mendel’s laws : segregation and...'

The text states: 'Sutton and Boveri argued that the pairing and separation of a pair of chromosomes would lead to the segregation of a pair of factors they carried.'

The text mentions: 'He observed that the two genes did not segregate independently of each other and the F2 ratio deviated very significantly from the 9:3:3:1 ratio (expected when the two genes are independent). Morgan and his group knew that the genes were located on the X chromosome... and saw quickly that when the two genes in a dihybrid cross were situated on the same chromosome, the proportion of parental gene combinations were much higher than the non-parental.'

The study of chromosomes and their role in heredity falls under cytogenetics. Morgan's work directly linked gene behavior to chromosome behavior, a core aspect of cytogenetics.

The text explains: '...when the tall and dwarf plant produce gametes, by the process of meiosis, the alleles of the parental pair separate or segregate from each other and only one allele is transmitted to a gamete. This segregation of alleles is a random process...'