Structure of chromosomes

Chromosomes

Chromosomes are the highly coiled, ribbon like structures formed by the condensation of the chromatin fibre during cell division

Chromatin

The complex structure of one long DNA molecule associated with many proteins is called chromatin

Why the DNA is also called macromolecule?

A Single DNA molecule is very large and hence it's called macromolecule.

Nucleotide

Single unit of nucleic acid composed of phosphate, five carbon atoms and purine and PYRIMIDINE base

Four types of nitrogenous base in DNA

Adenine, guanine, cytosine, thymine

Histone

Histones are the protein that helps in the coiling and packaging of DNA into structural unit called nucleosomes.

What are nucleosome?

The complex structure consisting of a DNA strand and eight histone proteins is called nucleosome.

What are chromatids?

One vertical half of a duplicated chromosome is called a chromatid

What are sister chromatids?

Two identical chromatids that are joined by a centromere or called sister chromatids

Any two functions of centromere

It serves to attach the chromosome with the spindle fibres during the cell division... It also helps to detach the sister chromatids of the chromosome during anaphase stage.

What are genes?

Genes or specific sequences of nucleotide on a chromosome that encode particular proteins, which are expressed in the form of some particular feature of a body.

Cell cycle

The cell cycle is a series of events that take place in the cell leading to the duplication of its DNA and the subsequent division of the cell to produce to daughter cell

Interphase

The non-dividing phase of the cell where the cytoplasm in the daughter cell is comparatively less to mother cell

Also called as resting phase

Interphase

First growth phase

RNA and proteins are synthesised and the volume of cytoplasm increases. Also mitochondria and chloroplast Divide.

Synthesis phase

More DNA is synthesised and chromosomes are duplicated.

Second growth phase

RNA and proteins necessary for cell division continue to be synthesised and the cell is now ready to undergo cell division

Mitosis

Type of cell division where it produces the diploid cells for growth

Meiosis

Cell division Leading to the production of haploid cell or gametes.

Phases of mitosis

Karyokinesis and Cytokinesis.

Four phase of karyokinesis

Prophase, metaphase, anaphase, Telophase

Which type of phase?

Interphase

Chiasma

The point of attachment between two nonsister chromatids of a pair of homologous chromosome form during meiosis

Crossing over

The process of exchange of genetic material during meiosis between two nonsister chromatids of a pair of homologous chromosome