The number, size and shape arrangement of chromosomes is called Karyotype. Chromosomes are arranged according to shape and the diagram is called Karyogram. The scientific study of the chromosome set of organisms is called Karyology. The arrangement of chromosome sets is called Chromosome banding.

In 1921, scientist Theophilus Painter first published the number of human chromosomes. Less than 10% of living organisms have chromosome numbers counted. Chromosome 2n number can be 2-1600 depending on species characteristics. Each cell in higher organisms has 2-80 chromosomes. The number of chromosomes in the human body is 23 pairs or 46. Among them are 2 sex chromosomes and 44 autosomes.
The least number of chromosomes
1. Plants: Moss-Mucor heimalis 2n=2 and Haplopappus gracilis 2n=4
2. Animals: Ants-Myrmecia pilosula 2n=1 and roundworms- Ascaris megalocephalus sub. sp. univalens 2n=2
Maximum number of chromosomes
1. Plants: Poa littarosa 2n=506-530 and Fern-Ophioglossum reticulatum 2n=1260 |
2. Animals: Protozoa-Aulacantha (Olacantha sp.) 2n=1600 |
[A ciliated protozoa (Oxytrichatrifallax) has 2n = 16000+ chromosomes]

Chromosomes are usually 3.5-30 µm in length and 0.2-2.0 µm in diameter. Average human chromosome length is 4-6 µm, Drosophila chromosome length is 3 µm and Bhutra chromosome length is 8-12 µm. Lamp brush chromosomes are 1500-2000 micrometers in length. Polytene chromosomes are 2000 micrometers in length. Chromosome length of Trillium is 32 µm. At the metaphase stage of cell division, the chromosomes are thick, well-organized and clearly visible.

In 1842, Karl Nageli first observed chromosomes in the nucleus of plant cells. In 1875, scientist Strasburger first observed thread-like structures during cell division. He is called the inventor of chromosomes. In 1888, scientist Walter Fleming named the thread-like structure of the nucleus as chromatin. In 1888, scientist Wilhelm Waldeyer named it chromosome for its color-carrying capacity. In 1902, scientists Sutton and Boveri described chromosomes as the containers and carriers of heredity. In 1921, scientist Theophilus Painter first published the number of human chromosomes.

The word chromosome is formed from the Greek word chroma meaning color and soma meaning body. Chromosome means colored body or colored body. Chromosome is a small, replicable thread-like organelle composed of nucleoproteins located in the nucleus of a true cell that carries hereditary characteristics and is capable of causing variation and mutation. In primitive cells, the main component of chromosomes is DNA or adichromosomes.

The ratio of the total number of cells present in a tissue to the number of cells undergoing mitosis is called the mitotic index (MI). Cancer cells have a higher mitotic index than normal cells.

The meaning of the word Cancer is crab. Cancer cells look like crab legs when they spread around. Dysregulation of cyclin-cdk in cancer cells. Cancer cells make their own growth factors or do not need growth factors for cell division. Hence the possibility of cancer increases.

Cell death occurs in two ways. Necrosis and apoptosis. Cell death due to lack of nutrients or toxic substances is called necrosis. Apoptosis is the process of death of unnecessary cells or organs in the body. Apoptosis is the destruction or death of tissue between human fingers. Apoptosis causes red blood cells, white blood cells and platelets to die after a certain period of time.

The spread of cancer cells to different parts of the body is called metastasis. Malignant tumor cells that cause cancer spread through the blood and lymph to different parts of the body and form new tumors. Cancer formation is accelerated due to metastasis.

All substances or agents that cause cancer in the body are called carcinogenic agents. Carcinogenic agents like UV rays, cigarette tar, X-rays etc. These substances cause mutations or changes in genes. Mutagenic genes cause cancer.