Genetics And Plant Breeding - Study Mode
[#396] Double helix DNA exists due to
Correct Answer
(C) Both A and B
Explanation
Solution: Double helix DNA exists due to Hydrogen bonding between nitrogen bases, and base stacking interaction. Double-stranded DNA consists of two polynucleotides that are arranged such that the nitrogenous bases within one polynucleotide are attached to the nitrogenous bases within another polynucleotide by way of special chemical bonds called hydrogen bonds. Its double helix consists of two spiral chains of DNA. This double helix shape is often visualized as a spiral staircase.
[#397] The term self-incompatibility was coined by
Correct Answer
(A) Stout (1917)
Explanation
Solution: The term self-incompatibility was coined by Stout in 1917. Whereas it was first reported in Verbascum phoeniceum by Koelreuter in the middle of the 18 th century. Self-incompatibility (SI) is a general name for several genetic mechanisms that prevent self-fertilization in sexually reproducing organisms and thus encourage outcrossing and allogamy.
[#398] Identify the phenotypic ratio of Duplicate gene action.
Correct Answer
(B) 15 : 1
Explanation
Solution: The phenotypic ratio of Duplicate gene action is 15 : 1. In this cross, whenever a dominant allele is present at either locus, the biochemical conversion occurs, and a coloured kernel results. Thus, only the double homozygous recessive genotype produces a phenotype with no colour, and the resulting phenotypic ratio of colour to noncolour is 15 : 1 .
[#399] Which of the following is a macronutrient?
Correct Answer
(C) Magnesium
Explanation
Solution: Magnesium is the macronutrient among the given options. Magnesium (Mg) is one of three secondary macronutrients, along with calcium and sulphur, required for balanced crop nutrition. Mg 2+ plays a role in several physiological processes that support plant growth and development. Mg deficiencies can lead to reduced crop growth and yield. Magnesium deficiency is common in tomatoes, apples, grape vines, raspberries, roses and rhododendrons.
[#400] The situation in which one gene hides the effect of a second gene when both are present in a chromosome is called
Correct Answer
(B) Epistasis
Explanation
Solution: The situation in which one gene hides the effect of a second gene when both are present in a chromosome is called Epistasis. Epistasis is a phenomenon in genetics in which the effect of a gene mutation is dependent on the presence or absence of mutations in one or more other genes, respectively termed modifier genes. The concept of epistasis originated in genetics in 1907 but is now used in biochemistry, computational biology and evolutionary biology.