In a cluster of glowing human stem cells, one cell divides. The cell membrane is shown in purple, while DNA in the dividing nucleus is blue. The white fibers linking the nucleus are spindles, which aid in cell division.
Organisms are broadly classified into two domains – Eukaryota (include yeasts, humans and everything in between) and Prokaryota (include bacteria and archaea). At the cellular level, eukaryotic cells are more organized and have a nucleus within which the DNA is present in chromosomes whereas prokaryotes have their genetic material unencapsulated in the form of a nucleoid. Cells have organelles like the mitochondria, Endoplasmic Reticulum, Golgi apparatus, ribosomes etc. The mitochondrion is the powerhouse of the cell- responsible for ATP synthesis. It is common to both eukaryotes and prokaryotes; most of the genes in the mitochondrial genome are responsible for energy production and in most species, are inherited from the mother alone!
Cells are constantly dividing in order to replace dying cells. Every cell undergoes a cycle of changes from birth to death. Mitosis is the process of division of a cell into two identical daughter cells. Before this process, the DNA in the original cell must replicate forming two copies- ultimately separating during mitosis with one copy in each daughter cell. However, not all cells produce two copies of themselves! During developmental stages, hematopoietic stem cells divide and differentiate into different cell types.
Another interesting form of cell division is called meiosis that entails collection of two copies of chromosomes from both parents and recombination, where the chromosomes cross-over and result in a mixed chromosome in the daughter cell. There is at least one such cross-over per chromosome. This is the reason why families do not look identical!
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