Genetics And Plant Breeding - Study Mode
[#241] Reappearance of an ancestral trait after several generations because of recessiveness or masking effects is known as
Correct Answer
(B) Atavism
Explanation
Solution: The reappearance of an ancestral trait after several generations because of recessiveness or masking effects is known as Atavism. An atavism is a modification of a biological structure whereby an ancestral genetic trait reappears after having been lost through an evolutionary change in previous generations. Evolutionarily traits that have disappeared phenotypically do not necessarily disappear from an organism's DNA. The gene sequence often remains but is inactive. Such an unused gene may remain in the genome for many generations.
[#242] Pure line is the progeny of
Correct Answer
(D) Of nucleus seed
Explanation
Solution: The pure line is the progeny of the nucleus seed. Pure-line selection involves selecting and breeding progeny from superior organisms for several generations until a pure line of organisms with only the desired characteristics has been established. Nucleus Seed is the initial amount of pure seed of improved variety or parental lines of a hybrid produced under the supervision of the plant breeder who has evolved that variety or hybrid. The nucleus seed is genetically cent percent pure and does not contain other physical impurities.
[#243] The number of three way crosses are
Correct Answer
(A) $$frac{{{ ext{n}}left( {{ ext{n}} - 1}
ight)left( {{ ext{n}} - 2}
ight)}}{2}$$
[#244] Male sterility is used for the production of
Correct Answer
(A) Composite varieties
Explanation
Solution: Male sterility is used for the production of Composite varieties. A composite variety is a variety developed by mixing the seeds of various phenotypically outstanding lines possessing similarities in various characteristics like height, seed size, seed colour, maturity, etc. Genetic male sterility is widely used for hybrid seed production of both seed-propagated species and vegetatively propagated species.
[#245] Random assortment of genes will occurs when the gene are located on
Correct Answer
(B) Different chromosome
Explanation
Solution: A random assortment of genes will occur when the gene is located on a Different chromosome. Recombination scrambles pieces of maternal and paternal genes, which ensures that genes assort independently from one another. It is important to note that there is an exception to the law of independent and random assortment for genes that are located very close to one another on the same chromosome because of genetic linkage.