The term "chromosome" is derived from the Greek words meaning "colored body," referencing their ability to be stained by specific dyes.
Karl Nägeli first observed the rod-like structures within the plant cell nucleus in 1842.
The term "chromosome" was coined by W. Waldeyer in 1888.
In 1902, Walter Sutton and Theodor Boveri proposed that chromosomes serve as the physical carriers of genes in eukaryotic cells.
The number of chromosomes remains constant in all cells of a species. Gametes (e.g., sperm and eggs) have half the chromosome count of somatic cells and are referred to as a haploid set due to meiosis during sexual reproduction. The preservation of chromosome number is crucial in the mitotic division of somatic cells, which is necessary for an organism's growth, repair, and regeneration.
The number of chromosomes can vary among different species. Nematode species have only two chromosomes in their cells, while some protozoans may have as many as 1600 chromosomes. Most plant and animal species typically possess between 8 and 50 chromosomes in their somatic cells. The number of chromosomes doesn't necessarily reflect the complexity of a species. For example, human cells contain a total of 23 pairs of chromosomes, with 22 being autosomes and one being a sex chromosome.
Karyotyping is a technique used to examine the structure of chromosomes within a species. It involves isolating, staining, and photographing the chromosomes. This method is valuable for detecting any chromosomal abnormalities.
Chromosomes consist of histone proteins and DNA in terms of their chemical composition. Within each cell, there are pairs of these chromosomes, which are called homologous chromosomes. Chromosomes are composed of chromatin, a substance that encompasses a single DNA molecule along with associated proteins. Each chromosome contains numerous genes, often numbering in the hundreds or thousands, and these genes have the ability to code accurately for various proteins within the cell. The structure of a chromosome is most clearly observed during the process of cell division.
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