Biology Test - 2

Herpes simplex virus type 1 (HSV-1) is a double-stranded DNA (dsDNA) virus with a 152-kb linear genome. Replication of HSV-1 DNA takes place in the host nucleus. 

Reovirus is a nonenveloped double-stranded RNA virus. This virus was initially not known to be related to any specific disease, and so was named Respiratory Enteric Orphan virus.

The genome of the hepatitis delta virus (HDV) is the smallest known to infect man. Encoding just one protein, hepatitis delta antigen (HDAg), HDV relies heavily on host functions and on structural features of the viral RNA.

The rotavirus genome consists of 11 segments of double-stranded (ds) RNA and is contained in the viral core along with the minor structural proteins, VP1 and VP3 (10).

Root is the plant part that is formed from the radicle of the germinating seed and generally grows towards the soil. It has four main regions:

Root cap: It is a thimble like structure that covers the root apex. It protects the tender apex of the root while making its way through the soil.

Region of meristematic activity: It is a few millimeters above the root cap. The cells in this region are very small, thin-walled and have dense cytoplasm. Also, the cells divide repeatedly in this region.

Region of elongation: Cells proximal to the region of meristematic activity are a part of this region. These cells undergo rapid elongation and enlargement. So, this region is responsible for the growth of roots in length.

Region of maturation: This is the region proximal to the region of elongation. It also consists of fine, delicate, thread-like structures called root hairs for the absorption of water and minerals from the soil.

Ernst Mayr proposed the biological species concept, which defines species as groups of actually or potentially inter-breeding natural populations which are reproductively isolated from other such groups.

Reproductive isolation is a condition of speciation and the primary criterion of the biological species concept. In the well-known Ernst Mayr's definition, “species are groups of actually or potentially interbreeding natural populations, which are reproductively isolated from other such groups” (Mayr, 1942).

So, if both the assertion and the reason are true and the reason is a correct explanation of the assertion.

The pseudostratified epithelium is present in the trachea and bronchi. The pseudostratified epithelium is a type of epithelium that, though comprising only a single layer of cells, has its cell nuclei positioned in a manner suggestive of stratified epithelia. The nuclei of these cells, however, are disposed at different levels, thus creating the illusion of cellular stratification. Not all ciliated cells extend to the luminal surface, such cells are capable of cell division providing replacements for cells lost or damaged. Pseudostratified epithelial function in secretion or absorption. If a specimen looks stratified but has cilia, then it is a pseudostratified ciliated epithelium, since stratified epithelia do not have cilia.

During the process of evolution, development of trichogyne of algae could be traced as style of angiosperm.

A hairlike terminal process forming the receptive part of the female reproductive structure in certain fungi and algae. A hairlike terminal process forming the receptive part of the female reproductive structure in certain fungi and algae.

A normal Human has 23 pairs of chromosomes (46 chromosomes) out of which 22 pairs are autosomes or allosomes  (Non - sex chromosomes), while the 23rd pair is the sex chromosome which is responsible for the hereditary changes.

• One - One chromosome each in the sex chromosome pair comes from the maternal and paternal side respectively.
• Any deviation from this normal arrangement may result in a disorder or syndrome.
• These disorders may arise either by addition, deletion, or nonfunctioning of a single or multiple chromosomes.
• Examples of such disorders are Turner syndrome, Edward's syndrome, Patau's syndrome, Klinefelter's syndrome, etc.

The primary function of CSF is to cushion the brain within the skull and serve as a shock absorber for the central nervous system. CSF also circulates nutrients and chemicals filtered from the blood and removes waste products from the brain.

(i) Viroid - (c) T.O. Diener -Viroids are the smallest infectious pathogens known. They are composed solely of a short strand of circular, single-stranded RNA that has no protein coating. The term Viroid was introduced by T.O.Diener.

(ii) Cell - (b) Leeuwenhoek -Leeuwenhoek (1674), with the improved microscope, discovered the free-living cells in pond water for the first time. 

(iii) Virus - (d) Ivanowsky   - Dmitri Ivanovsky, in studying a disease that affects tobacco plants, paved the way for the discovery of the infectious particle known as a virus. A virus is a small infectious agent that replicates only inside the living cells of an organism.

(iv) The triple helical structure of collagen - (a) Ramachandran -collagen is the most abundant protein in your body. It is the major component of connective tissues that make up several body parts, including tendons, ligaments, skin, and muscles. Prof.Ramachandran proposed the  Triple helical structure of collagen.

The Dusky gopher frog, which is also known as the Mississippi gopher frog is a critically endangered species of frog in the family Ranidae. It is endemic to the Southern United States.

The life span of sperm after ejaculation depends on the circumstances. Ejaculated sperm remain viable for several days within the female reproductive tract. Fertilization is possible as long as the sperm remain alive for up to 5 days. Sperm can also be preserved for decades when semen is frozen.