Genetics And Plant Breeding - Study Mode

[#176] A mating among the following can not lead to heterosis
Correct Answer

(C) AABBccdd × AABBccdd

Explanation

Solution: Mating among the following cannot lead to heterosis is AABBccdd × AABBccdd. Heterosis refers to the phenomenon that progeny of diverse varieties of a species or crosses between species exhibit greater biomass, speed of development, and fertility than both parents. Various models have been posited to explain heterosis, including dominance, overdominance, and pseudo-overdominance.

[#177] Heriditary variation in plants have been produced by the use of
Correct Answer

(D) Gama ray

Explanation

Solution: Hereditary variations in plants have been produced by the use of Gama ray, while others in options like, auxin, gibberellic acid and DDT are hormones and pesticides. Gamma radiation (GR) is one of the most widely used mutagenic agents in plants because it is reported to induce high genetic variability. This type of radiation can be generated by radioisotopes such as carbon-14 ( 14 C), cobalt-60 ( 60 Co), cesium-137 ( 137 Cs) and plutonium-239 ( 239 Pu).

[#178] Which of the following is Autotetraploid?
Correct Answer

(A) Cynodon dactylon

Explanation

Solution: Autotetraploid means a plant that has four sets of chromosomes , all derived from the same species . Imagine if a plant normally has two copies of each chromosome (diploid), an autotetraploid has four copies of each chromosome, all from its own kind. Let's break down the options: A) Cynodon dactylon (Bermuda grass): This is known to exist in tetraploid forms. It is an example of a plant with multiple sets of the same genome. B) Secale cereale (Rye): This is generally diploid , meaning it has two sets of chromosomes. C) Pisum sativum (Pea): This is also a common diploid plant. D) Raphanus (Radish): While some variations might exist, it's typically considered diploid . So, Cynodon dactylon is the best example of an autotetraploid from the options given because it naturally occurs with four sets of chromosomes from its own species.

[#179] First cotton hybrid variety in the world developed in India, the variety is
Correct Answer

(A) H4

Explanation

Solution: The first cotton hybrid variety in the world developed in India, the variety is H4. H4 is the world's first cotton hybrid released for commercial cultivation. Chandrakant T. Patel, (11 th July 1917 - 25 th December 1990) was a cotton scientist, who developed the first commercial cotton hybrid, known as Hybrid-4 in 1970, which was later cultivated commercially in the states of Gujarat and Maharashtra.

[#180] Which of the following stage of cell division resembles the 'Law of Segregation'?
Correct Answer

(B) Anaphase

Explanation

Solution: Anaphase is the stage of cell division that resembles the 'Law of segregation'. The law of segregation states that each individual that is a diploid has a pair of alleles (copy) for a particular trait. Each parent passes an allele at random to their offspring resulting in a diploid organism. The allele that contains the dominant trait determines the phenotype of the offspring. Mendel's Segregation law occurs in anaphase (I and II) of meiosis. It is a phase in the first meiotic division in which the homologous chromosomes are segregated into two daughter nuclei with their various versions of each gene.