Biology Test 123

Hornbill and Indian aconite is a pair of endangered species that are low in population number and are considered in danger of becoming extinct. They have been characterized by the International Union for Conservation of Nature red list as they are likely to become extinct.

Protosteles are the most complex type of stellar organization among all pteridophytes. They are solid steel with most origins, having a phloem-enclosed central xylem core. In their rhizome, stem or roots, most of the pteridophytes exhibit protostelic character.

A retrovirus is a single-stranded positive-sense RNA virus with a DNA intermediate. Most of a tumour causing viruses are retroviruses. After infecting a cell a retrovirus uses an enzyme called reverse transcriptase to convert its RNA into cDNA by the process of reverse transcription. The retrovirus then integrates its viral DNA into the DNA of the host cell, which allows the retrovirus to replicate.

Oxytocin (Oxt) is a peptide hormone and neuropeptide. It is normally produced in the hypothalamus and released by the posterior pituitary. It plays a role in social bonding, reproduction, childbirth, and the period after childbirth.

The Proximal convoluted tubule (PCT) which is the longest part of the renal tubule - has a simple tall cuboidal epithelium, with a brush border (microvilli). The epithelium almost fills the lumen, and the microvilli increase the surface area by 30-40 fold.

Histone proteins are the proteins that coil around the DNA in the eukaryotes and forms a rigid structure known as nucleosomes. The positively charged ends of the histones attract the negatively charged ends of the DNA and lead to tight packaging. This solenoid structure undergoes further coiling to produce a chromatin fiber of 30-80 nm and then a chromatid of 700 nm.

In the human body, the nerve cell is the longest cell. Nerve cells are also called neurons that are found in the nervous system. They can be up to 3 feet long.

Nerve cells are only present in animals. The nerve cell is an excitable and specialized cell of the nervous tissue which helps in the proper functioning of the brain and coordination of other parts of the body.

Extrachromosomal DNA is found in chloroplast and mitochondria. Extrachromosomal DNA is any DNA that is found outside of the nucleus of a cell. It is also referred to as extranuclear DNA or cytoplasmic DNA. Most DNA in an individual genome is found in chromosomes. Extrachromosomal DNA is often used in the research of replication because it is easy to identify and isolate.

The chloroplast has an internal membrane system made up of thylakoid membranes. Some of the thylakoid membranes are stacked one above the other and are called grana. They are embedded in a viscous ground substance called the stroma.