Genetics And Plant Breeding MCQ Question and Answer | Agriculture MCQ Question

The 'pure line' theory was proposed by Johannsen.
Wilhelm Johannsen was a Danish pharmacist, botanist, plant physiologist, and geneticist. He is best known for coining the terms gene, phenotype, and genotype, and for his 1903 "pure line" experiments in genetics.
A pure line is the progeny of a single self-fertilized homozygous plant.

The C₄ plants are more efficient than the C₃ plants because they lack photorespiration.
C₄ plants including maize, sugarcane, and sorghum avoid photorespiration by using another enzyme called PEP during the first step of carbon fixation. This step takes place in the mesophyll cells that are located close to the stomata where carbon dioxide and oxygen enter the plant.
Photorespiration happens in C₃ plants when the CO₂ concentration drops to about 50 ppm. The key enzyme that accomplishes the fixing of carbon is rubisco, and at low concentrations of CO₂, it begins to fix oxygen.

When chiasma frequency is 100%, the percentage of crossing over is 50%.
A chiasma is the point of contact, the physical link, between two chromatids belonging to homologous chromosomes. At a given chiasma, an exchange of genetic material can occur between both chromatids and is called a chromosomal crossover.
When chiasma is organized in between two gene loci, only 50% of meiotic products shall be crossovers and 50% non-crossovers. Thus, the chiasma frequency is twice the frequency of cross-over products, therefore, when the chiasma frequency is 100%, the percentage of crossing-over is halved i.e. 50%.

A genophore is made up of ss or dsDNA.
A genophore is the DNA of a prokaryote. It is commonly referred to as a prokaryotic chromosome.
It is made up of single or double stranded circular supercoiled DNA.

The ovule is attached to the placenta with a slender stalk, known as the Hilum.
A hilum is a scar or mark left on a seed coat by the former attachment to the ovary wall or the funiculus. Hilum represents the junction of the ovule with the funicle in a seed.
A hilum can also be a nucleus of a starch grain; the point around which layers of starch are deposited. On a bean seed, the hilum is called the "eye".

If a female plant of genetic constitution AABB is crossed to a male plant of genetic constitution aabb and the F₁ is test crossed, the genetic constitution of the test crossed progenies will be 1AaBb : 1Aabb : 1aaBb : 1aabb.
Under the law of dominance in genetics, an individual expressing a dominant phenotype could contain either two copies of the dominant allele (homozygous dominant) or one copy of each dominant and recessive allele (heterozygous dominant). By performing a test cross, one can determine whether the individual is heterozygous or homozygous dominant.
The test cross ratio obtained by crossing AABB X aabb will be 1 : 1 : 1 : 1.

Abscisic acid hormone suppresses the growth of the plant.
Abscisic acid (ABA) is a plant hormone that regulates numerous aspects of plant growth, development, and stress responses.
Seed germination is inhibited by ABA in antagonism with gibberellin. ABA also prevents the loss of seed dormancy.
Abscisic acid is also produced in the roots in response to decreased soil water potential and other situations in which the plant may be under stress.

The sources of male sterility include failure of another dehiscence, nonfunctional pollen grains, etc.
But it is not caused by Spontaneous mutations, Induced mutations, and Interspecific crosses.
Male sterility (CMS), a condition under which a plant is unable to produce functional pollen, is widespread among higher plants.
Male-sterility plants provide crucial breeding tools to harness hybrid vigor, or heterosis, in hybrid crops and also provide important materials to study stamen and pollen development and cytoplasmic-nuclear genomic interactions.

Photolysis of water happens in PS-II.
Photosystem II is the first protein complex in the light-dependent reactions of oxygenic photosynthesis.
Within the photosystem, enzymes capture photons of light to energize electrons, and these energized electrons are replaced by oxidizing water to form hydrogen ions and molecular oxygen. That is photolysis means the breakdown of water in the presence of light.

Double top cross refers to (A × B) × OPV.
Double top crosses are the cross between a single cross and another inbred.
The first generation resulted from the controlled crossing of a certified single cross (A X B) and a certified open-pollinated variety (OPV).