Viability refers to the ability to germinate when environmental conditions are favourable to the plant. Thus, pollen viability refers to the percentage of pollens produced that are viable.

The period for which pollen grains remain viable is highly variable and to some extent depends on the prevailing temperature and humidity. In some cereals such as rice and wheat, pollen grains lose viability within 30 minutes of their release, and in some members of Rosaceae, Leguminoseae and Solanaceae, they maintain viability for months.

The tapetum is the innermost layer of the microsporangium. It provides nutrition to the developing pollen grains. It secretes enzymes, hormones and special proteins for the pollen grains to recognise compatibility. It also produces the exine layer of the pollen grains, which is composed of the sporopollenin.

he formation of fruits without fertilization is called parthenocarpy. Such fruits are either seedless or non-viable seeds. Parthenocarpy is of two types :

(1) Natural parthenocarpy : When seedless fruits are produced without any special treatment from the ovaries in the absence of pollination and fertilization, the phenomenon is called natural parthenocarpy. e.g., Grapes, Banana, Pineapple and Noval oranges.

(2) Induced parthenocarpy : When seedless fruits are produced by spraying the flowers with either water extract of pollen grains or growth promoting hormones such as Indole acetic acid (IAA), Naphthalene acetic acid (NAA), Gibberellic acid (GA), etc. the phenomenon is called induced parthenocarpy. e.g., Tomato, Black berry, Fig, Lemon, Apple, Orange, Pear. etc.

Flower is a modified stem which functions as a reproductive organ and produces ova and/or pollen. A typical angiospermic flower consists of four whorls of floral appendages attached on the receptacle: calyx, corolla, androecium (male reproductive organ consisting of stamens) and gynoecium (composed of ovary, style and stigma) .

RNA interference (RNAi) is a mechanism for sequence-specific gene silencing triggered by double-stranded (ds) RNA. RNAi constitutes an effective antiviral defense mechanism in many organisms. Accordingly, viruses interact with the RNAi pathway at different levels. In the process of silencing of mRNA, a eukaryotic cell produces a strand of RNA which is complimentary to the mRNA of the parasite, thus making it's RNA double stranded. This inhibits the parasite to translate it's RNA to any kind of protein and thus it prevents infection.

A n s w e r :

dsRNA gain entry into eukaryotic cell either through:
(i) infection by virus having RNA genome or
(ii) mobile genetic elements (transposons) that replicate via an RNA intermediate.

Cry and cry are different. Cry refers to the protein whereas cry is the gene of bacterium Bacillus thuringiensis. As this gene encodes for the crystal protein and hence named cry after crystal. 

Application of Biotechnology in Agriculture involves scientific techniques such as Genetically Modified Organisms, Bt Cotton, Pest Resistant Plants. It helps in modifying plants, animals, and microorganisms and improve their agricultural productivity. Techniques like vaccines, tissue culture, genetic engineering are also used.

Exons are the parts of the gene which represent the codons for creating the protein. Exons are parts of DNA which are converted into mature mRNA. The process by which DNA is used as a template to create mRNA is called transcription.

Sporogenesis is the formation of spores. Formation of microspores is called microsporogenesis and formation of megaspores is called megasporogenesis. Microspores are formed in the anther and develop into pollen grains whereas megaspores are formed inside the ovule and develop into embryo sac. Thus, sporogenesis involves the formation and development of spores.

1. Incomplete Dominance is the condition when neither of the alleles is dominant, rather combine and display a new trait by mixing of the two alleles. Co-Dominance is the condition when both the alleles of a gene are dominant, and the traits are equally expressed.
2. In Incomplete Dominance, neither of both the allele is dominant and give a new trait. In Co-Dominance both the alleles are fully dominant.
3. Incomplete Dominance is seen in Snapdragon, Mirabilis Jalapa, while Co-Dominance is seen in Roan character in cattle, A and B blood the group in human.
4. In the case of Incomplete Dominance both the allele blend their effect, but one of the two is more noticeable. But in the case of Co-Dominance, both the alleles equally blend to show their equal effects.
5. The hybrid will always give rise to new phenotype, even the intermediate effect is seen of the hybrid of the two alleles, and the new phenotypes contain no alleles of its own in case of incomplete dominance. On the contrary, there is no formation of new phenotype; even the independent effect is produced of the two alleles in Co-Dominancy.

Both deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are made up of nucleotides which consist of three parts:

• Nitrogenous Base. Purines and pyrimidines are the two categories of nitrogenous bases. ...
• Pentose Sugar. In DNA, the sugar is 2'-deoxyribose. ...
• Phosphate Group. A single phosphate group is PO43-.

The set of chromosomes in a cell makes up its genome; the human genome has approximately 3 billion base pairs of DNA arranged into 46 chromosomes. The information carried by DNA is held in the sequence of pieces of DNA called genes.

The genetic term was coined in 1905 by the English biologist William Bateson. He also described the study of heredity.

1) In Maize, the flowers are pollinated by wind. Therefore, the flowers are small, inconspicuous, unisexual, colourless and odourless.
2) In Wheat, the flowers are self-pollinated. The Anther and Stigma of the bisexual flowers of same plant mature before the opening of flower-bud and ensure the self-pollination.

A cross between two types of plants of same species considering only the transmission of one character is called monohybrid cross. For example, a cross between tall pea plants and dwarf pea plant that is considering only the height of the parents is a monohybrid cross. It will result in the formation of tall offsprings but they will be hybrid.

Representation of the monohybrid cross: character in focus is the height

Parents-     TT   X   tt

              (Tall)        (dwarf)

F1​-                     Tt

                  (Heterozygous tall)

On selfing:

                              Tt   X    Tt

F2​-                    TT   Tt    Tt     tt

Phenotypic ratio- 3 tall: 1 dwarf

Genotypic ratio- 1 homozygous tall: 2 heterozygous tall: 1 homozygous recessive

Functions of RNA

The ribonucleic acid – RNA, which are mainly composed of nucleic acids, are involved in a variety of functions within the cell and are found in all living organisms including bacteria, viruses, plants, and animals. These nucleic acid functions as a structural molecule in cell organelles and are also involved in the catalysis of biochemical reactions. The different types of RNA are involved in various cellular process. The primary functions of RNA:

• Facilitate the translation of DNA into proteins
• Functions as an adapter molecule in  protein synthesis
• Serves as a messenger between the DNA and the ribosomes.
• They are the carrier of genetic information in all living cells
• Promotes the ribosomes to choose the right amino acid which is required in building up of new proteins in the body.

• RNA is made up of ribose sugar (plz see the attachment for its structure )
• Whereas , DNA is made up of de oxy ribose sugar. (please see the attachment for its structure)
• Due to the presence of –OH group in the ribose sugar, it is more active.
•  
• Also, the nitrogenous base is hydrophobic whereas the sugar end and the phosphoric acid end present in both RNA & DNA is hydrophilic.
•  
• Nitrogenous base always wants to stay away from the universal solvent.

Since DNA is double stranded, it has its nitrogenous base in the interior of both the strands , thus keeping it away from water.

But RNA is single stranded, hence its nitrogenous base is not away from water, and thus is reactive.

• S strain
  • Smooth mucous polysaccharide coat
  • Resistant to immune system
  • Virulent
• R strain
  • Lacks the coat
  • Destroyed by immune system of the host
  • Non-virulent

Malaria is caused by the Plasmodium parasite. The parasite can be spread to humans through the bites of infected mosquitoes. There are many different types of plasmodium parasite, but only 5 types cause malaria in humans.

Sporopollenin is the most resistant known biological material which is found in the exine of the pollen grains. Sporopollenin is resistant to chemical and microbial decomposition. Thus, it can withstand high temperatures and strong acids and alkalies.