Genetics And Plant Breeding — Part 1 MCQs with Explanations

Genetic code was discovered by Holley, Nirenberg and Khorana. Marshall Nirenberg, Har Gobind Khorana, and their colleagues were the first to determine the genetic code and show how the nucleic acid bases determine the sequence of the 20 different amino acids during protein synthesis. Each gene's code uses the four nucleotide bases of DNA: adenine (A), cytosine (C), guanine (G) and thymine (T) in various ways to spell out three-letter “codons” that specify which amino acid is needed at each position within a protein.

The progeny of the breeder seed is referred to as the Foundation seed . The progeny of breeder seed is produced by recognized seed-producing agencies in the public and private sector, under the supervision of seed certification agencies in such a way that its quality is maintained according to prescribed field and seed standards. A certified seed shall be the progeny of foundation seed and its products shall be so handled as to maintain specific genetic identity and purity according to the standards prescribed for the crop being certified.

The molecular basis of organ differentiation depends on the modulation in transcription by the Transcription factor . A transcription factor is a molecule that controls the activity of a gene by determining whether the gene's DNA (deoxyribonucleic acid) is transcribed into RNA (ribonucleic acid). Proteins are involved in the process of converting, or transcribing, DNA into RNA. Transcription factors include a wide number of proteins, excluding RNA polymerase that initiate and regulate the transcription of genes.

The phenomenon of linkage was first observed by Bateson and Punnet in sweet pea in 1906. Linkage is the tendency for genes or segments of DNA closely positioned along a chromosome to segregate together at meiosis, and therefore be inherited together. The linkage between two or more loci controlling different desirable characteristics is advantageous for a plant breeder. A linkage between genes controlling two different desirable characters will help in the simultaneous improvement of both characters.

Examples of transposons in the human genome are Both LINE and SINE . Transposable elements (TEs) are mobile repetitive sequences that make up large fractions of mammalian genomes, including at least 45% of the human genome. SINEs and LINEs are short and long interspersed retro transposable elements, respectively, that invade new genomic sites using RNA intermediates. SINEs and LINEs are found in almost all eukaryotes and together account for at least 34% of the human genome.

The cell cycle is regulated by all of the above which are Cyclins, Cyclin-dependent kinase and Inhibitory proteins . The cell cycle is regulated by many cyclins, cyclin-dependent kinases (CDKs) as well as Inhibitory proteins which are a group of serine/threonine kinases. They form complexes with cyclins to stabilize, activate, and phosphorylate CDKs in specific phases. These are serine/threonine protein kinases that phosphorylate key substrates to promote DNA synthesis and mitotic progression.

Exosmosis takes place when a plant cell is put in a Hypertonic solution . Exosmosis is the movement of solvent out of the cell. Due to exosmosis, the cell shrinks. Exosmosis occurs in the presence of hypertonic solutions. This happens because the solute concentration of the surrounding solution is higher than that inside the cytoplasm.

The correct option is a-2, b-1, c-4, d-3. a) Artificial hybridization of radish ( Raphanus sativus ) and cabbage ( Brassica oleracea ) (both 2N = 18) produces a sterile first-generation hybrid with one diploid chromosome set from either parent. Tetraploidization eventually produces a stable, true-breeding hybrid Raphanobrassica . b) Nicotiana digluta was produced by pollinating a triploid Nicotiana Tabacum plant (2n = 72) with N. glutinosa. N. glutinosa × N. Tabacum = N. digluta. c) Triticale is a hybrid of wheat ( Triticum aestivum ) and rye ( Secale cerele ) first bred in laboratories during the late 19 th century in Scotland and Germany. When crossing wheat and rye, wheat is used as the female parent and rye as the male parent (pollen donor). d) Gossypium hirsutum , also known as upland cotton or Mexican cotton. It is a cross-bred cultivar (Gossypium harbaceum × Gossypium Raimondii) with varying fibre lengths and tolerances to several growing conditions.

The concept of a multiline cultivar was developed by Jensen (1952) . The concept of the multiline as an approach to the long-term control of diseases in self-pollinated crops was first presented by Jensen, 1952 in oats and next by Borlaug and Gibler (1953) in wheat. The multiline approach is concerned with the management of resistance genes that condition vertical resistance. Multiline crop cultivars are phenotypically similar (height, grain type) but genetically different against insect pests and diseases.

Of the total water uptake by a plant, passive absorption of water accounts for 98%. Passive absorption occurs due to osmosis usually when the rate of transpiration is typically higher than normal. In this way, water is transported from the roots to the leaves of the plants through the xylem tissue. It occurs more rapidly because of the transpiration pull and by the action of cohesive and adhesive force in water molecules that enables the continuous flow of water.

The Law of homologous series' is given by Vavilov . The law of homologous series was formulated by N. I. Vavilov in 1920. The Journal of Genetics published Vavilov's paper in 1922. This law established a parallel variability of homologous characters in taxonomically near species. The Law of homologous series states that a particular variation observed in a crop species is also expected to be available in its related species.

Wheat varieties KML 7404, and MLKS-11 are Multiline cultivars . Multiline crop cultivars are phenotypically similar (height, grain type) but genetically different against insect pests and diseases (Browning and Frey 1981; Wolfe 1985). Multiline cultivars have been developed for commercial cultivation in oats, wheat, soybean, and peanut. KML 7404 and MLKS-11 are wheat multiline varieties for the northern and northwestern plains of India. MLKS-11 is a mixture of eight components derived from Kalyan Sona.

The term chromosome was given by Waldayer . A chromosome is a long DNA molecule with part or all of the genetic material of an organism. Most eukaryotic chromosomes include packaging proteins called histones which, aided by chaperone proteins, bind to and condense the DNA molecule to maintain its integrity. W. Waldeyer coined the term "chromosome" in 1888.

DNA polymerase I was discovered by Kornberg . Arthur Kornberg, a prolific researcher who described his career as a “love affair with enzymes,” discovered DNA polymerase, an enzyme critical to DNA replication. For his discovery, Kornberg shared the 1959 Nobel Prize in Physiology or Medicine with Severo Ochoa, who discovered RNA polymerase I. this enzyme is also referred to as Kornberg enzyme.

Lysine is a limiting amino acid in Cereals . Cereals contain low amounts of lysine, and consequently, lysine is often the first limiting amino acid in diets that are high in cereals. Lysine is an essential amino acid, meaning it is necessary for human health, but the body cannot make it.

For the induction of mutations in crop plants, X-rays were first used by H. J. Muller (1927). Mutation involves sudden changes in an organism's genetic code. Herman Muller studied the hereditary characteristics of fruit flies and, in 1927, discovered that the number of genetic mutations observed in fruit flies increased when they were exposed to x-rays. Hermann Joseph Muller conducted three experiments in 1926 and 1927 that demonstrated that exposure to x-rays, a form of high-energy radiation, can cause genetic mutations, and changes to an organism's genome, particularly in egg and sperm cells.

The variety of wheat developed from spring × winter wheat crosses is termed VEERY . The ‘Veery’ lines resulted from a cross between a Russian winter wheat, ‘Kavkaz’, and a Mexican spring wheat, ‘Buho’. These new lines showed improved resistance to stripe and leaf rust pathogens, which helped create the second generation of high-yielding wheat.

Cryopreservation cannot be done for Aerobic microorganisms. Cryopreservation is a process where organelles, cells, tissues, extracellular matrix, organs, or any other biological constructs susceptible to damage caused by unregulated chemical kinetics are preserved by cooling to very low temperatures. Cells might be damaged if the intracellular concentration of solutes is high. The leakage of certain solutes from the cell during freezing should be checked. The physiological status of the plant material is also essential.

The objectionable weed in Oat is Avena fatua . Objectionable weed is also known as Satellite weed. Objectionable weed: A noxious weed, whose seeds are difficult to separate, once mixed with crop seeds. The weeds that mature at the same time & height as a host plant have a similar size and shape as the crop seeds. Wild oat (Avena fatua) is common in spring wheat (Triticum aestivum.

When the development of fruit occurs without fertilization, is known as Parthenocarpy . In some plants, however, the fruit develops without fertilization, a phenomenon is known as parthenocarpy. Parthenocarpic fruit has advantages over seeded fruit, longer shelf life and greater consumer appeal. SEEDLESS FRUIT such as navel oranges is propagated asexually, usually by grafting. Parthenogenesis occurs when there is less availability of functional eggs or sperms or when pollination fails to occur.

Self Incompatibility is controlled by two genes found in Gramineae . Self-incompatibility (SI) is defined as the inability to produce zygotes after self-pollination in a fertile hermaphrodite plant, which has stamens and pistils in the same flower. This structural organization of the hermaphrodite flower increases the risk of self-pollination, leading to low genetic diversity. SI is controlled by genes at the S-locus. The S-LOCUS RECEPTOR KINASE (SRK) gene encodes a serine/threonine kinase localized in the plasma membrane of the stigma epidermis.

The polar nucleus in embryosac is Diploid . There are seven cells in the embryo sac. These include three antipodal cells, one central cell (formed by the fusion of 2 polar nuclei), two synergid cells and one egg cell. Of the two polar nuclei present in the central cell, one is derived from the micropylar end and the other from the chalazal end. The cell contains two polar nuclei which often fuse to form a single diploid secondary or fusion nucleus.

During meiosis, the chromosome number is Halved . In meiosis, a cell containing a diploid number of chromosomes is converted into four cells, each having a haploid number of chromosomes. In human cells undergoing meiosis, for instance, a cell containing 46 chromosomes yields four cells, each with 23 chromosomes.

The seed multiplication rate for Ragi is 420 . The seed Multiplication Ratio is the number of seeds to be produced from a single seed when it is sown and harvested. At the time of the release of a variety, a small quantity of seed normally known as nucleus seed is available with the plant breeder.

A number of meiosis required to produce 102 pollen grains is 26. Meiosis division leads to the formation of 4 daughter cells, therefore a pollen grain on meiotic division produces 4 pollen grains. Thus, 25 pollen grains produce 100 new pollen grains, but according to the question, the required number of pollen is 102, therefore 26 meiotic divisions will produce the required number of pollen grains.

Cytoplasmic and genetic male sterility is exploited in hybrid seed production. Cytoplasmic male sterility (CMS), a condition under which a plant is unable to produce functional pollen, is widespread among higher plants. CMS systems represent a valuable tool in the production of hybrid seeds in self-pollinating crop species, including maize, rice, cotton and several vegetable crops. Genetic male sterility (GMS) has emerged as an ideal tool to accelerate hybrid breeding. Male sterility is generally characterized by the impairment of male reproductive development as a result of underlying genetic causes and leads to the malformation of male gametes and/or pollen.

Gregor Mendel , known as the father of genetics , presented his groundbreaking work on inheritance in pea plants in the year 1865 . He delivered his paper titled "Experiments on Plant Hybridization" to the Natural History Society of Brünn in two meetings held on February 8 and March 8, 1865 . Although the paper was published in 1866 , the actual presentation was made in 1865 . This work laid the foundation for the modern science of genetics . Hence, the correct answer is 1865 .

Molybdenum plays a major role in Nitrogen fixation . Mo is the component of meta-protein nitrogenase which helps the process of biological nitrogen fixation and acts as an essential component needed for N bacteria metabolism. The nitrogenase enzyme needs the Mo element in the process of its metabolism, which acts as an electron carrier between the oxidized and reduction stages.

The term recurrent selection was coined by Hull in 1945 . He proposed a breeding method that was termed "recurrent selection for specific combining ability." Recurrent selection means repeated cycles of selection and breeding aimed at the gradual genetic improvement of a few key traits in a single species. The benefits of breeding are cumulative in that each cycle or generation of improvement builds upon advances made in prior generations.

The terms horizontal resistance and vertical resistance were first used by Van Der Plank in 1963 . The term vertical resistance, used commonly in the context of plant selection, was first used by J. E. Vanderplank to describe single-gene resistance. This contrasted with the term horizontal resistance which was used to describe many-gene resistance. Genetic resistance that is effective at preventing successful attack only by certain races of a pathogen is called specific or vertical resistance, whereas resistance that is effective at preventing successful attack by all races of a pathogen is called general or horizontal resistance.

The crossing-over takes place in Pachytene . Pachytene is the stage of meiotic prophase that immediately follows the zygotene and is characterized by paired chromosomes thickened and visibly divided into chromatids and by the occurrence of crossing-over. During this stage, exchanges of chromosome material between maternal and paternal homologous chromosomes occur by crossing over. At the points of crossing over, bridges (chiasmata) are seen in variable numbers. Depending on the chiasmata, different aspects of the chromosomes can be observed.

The increased performance of F 1 hybrid over its parents is called Heterosis . 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.

If the host plant is susceptible to the pathogen at a young age and becomes resistant with age then it possesses Adult plant resistance . Resistance is the ability of a plant variety to restrict the growth and development of a specified pest or pathogen and/or the damage they cause when compared to susceptible plant varieties under similar environmental conditions and pest or pathogen pressure.

Out of the following given options Ribozyme is not a protein. Ribozymes are catalytically active RNA molecules or RNA-protein complexes, in which solely the RNA provides catalytic activity. The term ribozyme refers to the enzymatic activity and ribonucleic acid nature at the same time. Ribozymes are found in the genomes of species from all kingdoms of life.

Distant hybridization is associated with Hybrid inviability, Hybrid sterility and Hybrid breakdown. Distant hybridization refers to crosses between two different species, genera, or higher-ranking taxa, which can break species limits, increase genetic variation, and combine the biological characteristics of existing species. Hybrid inviability is a post-zygotic barrier, which reduces a hybrid's capacity to mature into a healthy, fit adult. Hybrid sterility is defined as the inhibition or suppression of the reproductive capacity of F1 or later-generation hybrids between genetically different strains or populations, usually belonging to different species. The hybrid breakdown is a type of reproductive failure that appears after the F2 generation of crosses between different species or subspecies. It is caused by incompatibility between interacting genes.

Rice inflorescence is called a Panicle . Panicles form the rice inflorescence. It is the top part of the rice plant, carried on the last inter-node. Panicles are composed of primary ramifications (small branches) that carry secondary branches themselves carrying the pedicels which carry the spikelets. The inflorescence of the rice plant is borne on terminal shoots and is thus called a panicle. It is the determinate type and at maturity, it is droopy.

The first sorghum hybrid was released in 1964 . Sorghum hybrid development involves the development of parental lines based on a cytoplasmic male sterile system including the pollen parent (R-line) and seed parents (A- and B-lines). The spread of modern hybrids and varieties of sorghum in India began in the late 1960s, with the release in 1964 of the first high-yielding hybrid CSH-1 developed by Dr. N. Ganga Prasada Rao, and the equally high-yielding variety Swarna in 1968, also developed by him.

The maize inbreeds are maintained by Selfing . The nucleus seed of inbred lines can be maintained by self-pollination, sib-pollination, or a combination of the two procedures (hand pollination). Some breeders prefer 'sibbing" because it maintains vigour. "Selfing" is used to stabilize inbred lines if a change in breeding behavior is noticed. Selfing or self-pollination, where ovules are pollinated by the plant's pollen, is the ultimate form of inbreeding or mating between relatives.

Diffused centromere means Centromere is nonlocalized and spread over the chromosome. Diffuse centromeres - in asexual organisms where the offspring is an exact genetic copy of the parent, there are limited sources of genetic variability. The chromosomes are characterized by large size, sinuous shape, and sticky matrix; the chromatids are parallel at anaphase, separate at metaphase throughout their length; the centromere is 'diffuse'.

The seeds that cannot be used in second generation is hybrid seeds . Hybrid seed production is predominant in modern agriculture and home gardening. All of the hybrid seeds planted by the farmer will produce similar plants, while the seeds of the next generation from those hybrids will not consistently have the desired characteristics. Hybrids are chosen to improve the characteristics of the resulting plants, such as better yield, greater uniformity, improved colour and disease resistance.