Biology Test - 1

Green manures are the crops that are grown primarily for building and maintaining soil fertility and structure. Green manure crops should be such that they can be grown quickly. Green manure crops include legumes such as vetch, clover, beans and peas; grasses such as annual ryegrass, oats, rapeseed, winter wheat and winter rye and buckwheat. Green manure crops provide nitrogen as the major nutrient.

Gonadotropin-releasing hormones secrete Follicle-stimulating hormones (FSH) and luteinizing hormones (LH) from the hypothalamus. In the process of spermatogenesis, these hormones are required. FSH acts on Sertoli cells, whereas LH acts on Leydig cells of the testis and stimulates The method of spermatogenesis gets stimulated by FSH and LH. Gonadotropins FSH and LH are secreted by the anterior pituitary. FSH promotes spermatogenesis in the seminiferous tubules and LH promotes androgen production in the interstitial cells (androgens are required for attainment of reproductive maturity in males).

Extranuclear DNA is found in chloroplast and mitochondria. Chloroplast and mitochondria contain genes that are transmitted from parents to the offspring along with the cytoplasm of the contributing gametes. Those genes are called plasma genes or extranuclear genes. They are collectively called a plasmon. They result in cytoplasmic or extranuclear inheritance.

A pure tall plant can be differentiated from a hybrid tall plant by self pollination. Pure breeding varieties are the one that carries same allele for a particular character and pass the trait without change from one generation to next upon selfing. For example, pure breeding tall (TT) plant carries two copies of “T” allele and selfing of these plants produce a uniform progeny of tall plants only. Hybrids are the one which carries contrasting allele of a particular gene; for example, hybrid tall plant’s genotype is “Tt”. Segregation of these contrasting factors of hybrid produces both tall and dwarf plants in the progeny. Pure breeding and hybrid dominant exhibit same phenotype. The absence of dwarf allele (t) in pure breeding tall plants rules out the possibility of the appearance of dwarf plants upon selfing.

Fungi is heterotrophic eukaryotic organisms.

Fungi are not capable of photosynthesis they are heterotrophic because they use complex organic compounds as sources of energy and carbon. Fungi cannot produce their own food, they must acquire carbohydrates and other nutrients from the animals, plants, or decaying matter on which they live.

During the S phase or synthetic phase of interphase, replication of DNA and synthesis of histone proteins occur. New histones are required in massive amounts immediately at the beginning of the S period of DNA synthesis to provide the new DNA with nucleosomes. At the end of the S phase, each chromosome has two DNA molecules and a duplicate set of genes. S phase occupies roughly 35 to 45 percent time of the cell cycle.

Spermatheca is absent in male cockroaches.

A pair of spermatheca is present in the 6th segment of female cockroaches. This segment opens into the genital chamber. The spermatheca is used to receive sperm from the male body and store it in the body of a female cockroach.

Thallophyta do not have a well-differentiated body design and are the simplest of plants. Thallophyta is a division of the plant kingdom including primitive forms of plant life showing a simple plant body. Including unicellular to large algae, fungi, lichens. They are simple plants without roots stems or leaves. They are non-embryophyta. These plants grow mainly in water.

If more than a single embryo is present in one seed, the phenomenon is known as polyembryony. It is usually seen in some varieties of citrus fruits as well as mango. It plays a crucial role in the breeding of plants and horticulture. These embryos can give birth to healthy plantlets free of viruses. Hybrid species of these plants and fruits are grown extensively nowadays. The varieties obtained through this method are extremely productive.

Vaccines prepared through recombinant DNA technology are called third generation vaccine.

Third-generation vaccines are those in which recombinant techniques are used for the production of vaccines. In this technique DNA encoding, the antigen is inserted into a vector which will be recognized as a pathogen in the host. Such that the host immune system generates an immune response against the vector and thereby the antigen.