Genetics And Plant Breeding - Study Mode

[#301] In India for hybrid seed production inmaizewe use
Correct Answer

(B) Cytoplasmic genetic male sterility

Explanation

Solution: In India, for hybrid seed production in maize, we use Cytoplasmic genetic male sterility. The cytoplasmic-genetic male sterility is used commercially to produce hybrid seed in maize, bajra and jowar. A triple cross may be produced by crossing a single cross with fertility restoring inbred so that all the plants in the triple cross would be male fertile.

[#302] In the mechanism of opening and closing of stomata, the important factor is
Correct Answer

(A) The shape of the guard cells

Explanation

Solution: In the mechanism of opening and closing of stomata, the important factor is the shape of the guard cells. When the concentration of potassium ions increases in the guard cell, it allows the guard cell to absorb water from the surrounding cells. This turgidity of the guard cell cause opening of the stomata. However, decrease in the concentration of potassium ions, makes guard cell flaccid and ultimately makes it close.

[#303] Match the following columns: Column I (Scientist) Column II (Discovery) a. Shull 1. DNA model b. Waldyer 2. First hybrid c. Fairchild 3. Heterosis d. Watson and Crick 4. Chromosome
Correct Answer

(B) a-3, b-4, c-2, d-1

Explanation

Solution: a. Shull discovered Heterosis. George Harrison Shull was an eminent American plant geneticist. He also described heterosis in maize in 1908 and made several other key discoveries in the emerging field of genetics. b. Waldeyer discovered Chromosome. He coined 1888 the term "chromosome" to describe them. Among his many other anatomical and embryological studies. c. Fairchild discovered the first hybrid. In 1716 - 17 he was the first person to scientifically produce an artificial hybrid, Dianthus Caryophyllus barbatus, known as "Fairchild's Mule", a cross between a Sweet William (Dianthus barbatus) and a Carnation pink. d. Watson and crick discovered a model of DNA. The discovery in 1953 of the double helix, the twisted-ladder structure of deoxyribonucleic acid, by James Watson and Francis Crick marked a milestone in the history of science.

[#304] In wheat, production of foundation seed needs an isolation distance of
Correct Answer

(B) 3 m

Explanation

Solution: In wheat, the production of foundation seed needs an isolation distance of 3 m. Maintain a minimum isolation distance of three meters of seed plot of a variety with other varieties to avoid possible out-crossing and admixture. Isolation distance is required to separate a wheat seed field from the same variety not conforming to the standard.

[#305] Nullisomic condition is represented by
Correct Answer

(C) 2n - 2

Explanation

Solution: Nullisomic condition is represented by 2n - 2. Nullisomic is a genetic condition involving the lack of both the normal chromosomal pairs for a species (2n - 2). Humans with this condition will not survive. It is caused by non-disjunction, during meiosis that causes two of the gametes to have no chromosomal material, leaving the other two gametes to have double the amount of chromosomal material.