Describe the structure of double helix model of DNA. DNA is made up of two polynucleotide chains, where the backbone is made up of sugar and phosphate groups.

What is linkage and recombination? Linkage- The physical Association of two genes on a chromosome is termed as linkage.

What is amniocentesis? A foetal sex-determination test based on the chromosome pattern in the cells found in amniotic fluid surrounding the developing embryo is called amniocentesis.

What is placenta. Mention the functions of placenta. A structural and functional unit present between developing embryo (foetus) and maternal body is called placenta.

What is apomixis and polyembryony? The phenomenon of asexual reproduction that imitates sexual reproduction by the formation of seed without fertilization is called apomixis or agamospermy.

What is parthenogenesis? The phenomenon of development of female gamete directly into an individual without
fertilization is called parthenogenesis.

Hardy-Weinberg principle states that allelic frequencies in a population are stable and remains constant from generation to generation, i.e., gene pool (total number of genes and their alleles in a population) is constant.

What is an allergy? The exaggerated response of the immune system to certain antigens present in the environment is called allergy.

What is an explant? The part of the plant taken for tissue culture is called explant.