Biology Test - 39

Phosphorus is a constituent of cell membranes, certain proteins, all nucleic acids and nucleotides

Hotspots are areas with high density of biodiversity or mega diversity which are also the most threatened ones. Ecologically hotspots are determined by four factors - number of species/ species diversity, degree of endemism, degree of threat to habitat due to its degradation and fragmentation, and degree of exploitation. India has three hotspots : Indo-Burma, Himalayas and Western Ghats - Sri Lanka. India is even otherwise a country of mega diversity with 2.4% of land area and having 8.1% of global diversity. Major centres of biodiversity are Agasthyamalai hills, Silent valley and Amambalam reserve. There is high degree of endemism as well as richness of species of flowering plants, amphibians, reptiles, some mammals and butterflies.

Reverse transcriptase onlyis used by the HIV to form DNA in the host cell.

Reverse transcriptase catalyzes the formation of DNA from an RNA template.It works completely opposite to transcriptase enzyme.It is a type of viral enzyme present in retrovirus.

Seeding involves the spread of cancer cells to serious membranes of body cavities.

Tumor seeding or needle seeding refers to rare occurrences when the needle inserted into a tumor during a biopsy dislodges and spreads cancer cells. It is sometimes called needle track or tract seeding because the cancer cells grow along the needle's track.

Indole-3-acetic acid (IAA, 3-IAA) is the most abundant and basic, naturally occurring, plant hormone of the auxin class.

IAA is predominantly produced in the apical bud of and young leaves of plants and is known to be an inducer of cell division and elongation.

IAA, as well as most other auxins, are also known to act in concert with, or in opposition to, other plant hormones.

Example: The ratio of auxin to cytokinin in certain plant tissues determines initiation of root versus shoot buds.

Glycolysis occurs in Cytoplasm part of the cell.

Glycolysis:

• The term glycolysis has originated from the Greek words,glycos for sugar, and lysis for splitting.
• The scheme of glycolysis was given byGustav Embden, Otto Meyerhof, and J. Parnas,and is often referred to as theEMP pathway.
• In anaerobic organisms, it is the only process inrespiration.
• Glycolysis occurs in the cytoplasm of the cell and is present in allliving organisms.
• In this process, glucose undergoes partial oxidation to form two molecules ofpyruvic acid.
• In plants, this glucose is derived from sucrose, which is the end product of photosynthesis, or fromstoragecarbohydrates.
• Sucrose is converted intoglucose and fructoseby the enzyme, invertase, and these twomonosaccharidesreadily enter theglycolytic pathway.
• Glucose and fructoseare phosphorylated to give rise toglucose-6- phosphateby the activity of theenzyme hexokinase.
• This phosphorylated form of glucose then isomerizes to producefructose-6- phosphate.
• Subsequent steps of the metabolism ofglucose and fructoseare the same.
• In glycolysis, a chain often reactions, under the control of different enzymes, takes place to producepyruvate from glucose.

The rod-shaped bacteria are called the Bacilli.

Bacteria are microscopic prokaryotes (single-celled organisms). They are the sole members of Kingdom Monera. Bacteria have variations in their shape, on the basis of their shape bacteria are of different types like :

1. Coccus/cocci:

• These bacteria are spherical or oval in shape.​
• These are the smallest bacteria. They are the most resistant bacteria (so, they are the most common).
• Eg - Diplococcus pneumoniae.

2. Bacillus/bacilli:

• This group includes most of the bacteria.
• They are Rod-shaped.
• Eg - E.coli, Bacillus anthracis

3. Spirillum:

• These are spiral-shaped bacteria.
• Eg - Spirillium volutans.

4. Vibrio: ​

• They are comma-shaped bacteria.
• Eg - Vibrio cholerae.

Monosomy and Trisomy can be explained as2 n - 1, 2 n + 1 =Trisomy.

Aneuploidyis of two types:

1. Hypoaneuploidy (loss)

• 2n - 1 = monosomy(loss of one chromosome only) i.e. the presence of a single copy of a particular chromosome. Eg -Turner's syndrome.
• 2n - 2 = Nullisomy(loss of a pair of the homologous chromosome)

2.Hyperaneuploidy (addition)

• 2n+1 = Trisomy:addition of one chromosome in one set. Eg -Down's syndrome
• 2n + 2 =Tetrasomy: addition of two chromosomes in one set.

An anther consists of four microsporangia.

Stamen, the male reproductive part of a flower. In all but a few extant angiosperms, the stamen consists of a long slender stalk, the filament, with a two-lobed anther at the tip. The anther consists of four saclike structures (microsporangia) that produce pollen for pollination.

Female gametophyte is also known as Embryo sac.

The female gametophyte is also commonly called the embryo sac or megagametophyte. The male gametophyte, also called the pollen grain or microgametophyte, develops within the anther and consists of two sperm cells encased within a vegetative cell (Gifford and Foster, 1989).