Biology Test - 64

In metacentric chromosomes the centromere is positioned in the centre making the arms of equal length. When the centromere is positioned slightly off centre this is called submetacentric.

If the number of chromosomes in most body cells of a mammal is 40, the cells in the seminiferous tubule will have While some other will have 20.

Idiogram is a composite photograph or diagram of metaphasic chromosomes of haploid or diploid set of an organism arranged in a series of decreasing size, thickness position of centron-iere and shape.

The kinetochore assembles on the centromere and links the chromosome to microtubule polymers from the mitotic spindle during mitosis and meiosis. Its proteins also help to hold the sister chromatids together and play a role in chromosome editing.

The centromere is the site of attachment of the chromosome to the spindle, and at anaphase the chromatids split apart at the centromere, and the two separate daughter chromosomes, as they are now known, move to the poles of the cell, so that one of each is incorporated into the daughter cells.

Human cells that contain one set of 23 chromosomes are called gametes, or sex cells; these eggs and sperm are designated n, or haploid.

A polynucleotide molecule is a biopolymer composed of 13 or more nucleotide monomers covalently bonded in a chain. DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) are examples of polynucleotides with distinct biological function.

Each bead of nucleosome has 200 bp of DNA which is wound 1.65 times around histone octamer. The 10 nm fibre of nucleosomes is coiled to form a 30 nm solenoid that has 6 nucleosomes per turn of the solenoid.

Most viruses have either RNA or DNA as their genetic material. The nucleic acid may be single- or double-stranded. The entire infectious virus particle, called a virion, consists of the nucleic acid and an outer shell of protein. The simplest viruses contain only enough RNA or DNA to encode four proteins.

Each chromosome is made up of DNA tightly coiled many times around proteins called histones that support its structure. ... Each chromosome has a constriction point called the centromere, which divides the chromosome into two sections, or “arms.” The short arm of the chromosome is labeled the “p arm.”