Cell as a Unit of Life

Interphase occurs just prior to cell division. Prepubertal male primordial germ cells are reactivated from interphase at puberty and enter rounds of mitoses followed by meiosis 1 and 2 to produce a unique haploid sperm.

Cyclin-dependent kinase inhibitor 1C (p57) is a tight-binding inhibitor of several G1 cyclin/Cdk complexes and a negative regulator of cell proliferation.

A resting phase where the cell has left the cycle and has stopped dividing.

A contractile ring, made of non-muscle myosin II and actin filaments, assembles equatorially (in the middle of the cell) at the cell cortex (adjacent to the cell membrane). Myosin II uses the free energy released when ATP is hydrolysed to move along these actin filaments, constricting the cell membrane to form a cleavage furrow.

Prometaphase is the phase of mitosis following prophase and preceding metaphase, in eukaryotic somatic cells. In prometaphase, the nuclear membrane breaks apart into numerous membrane vesicles and the chromosomes inside form protein structures called kinetochores.

Also known as the monarchial type of chromosomes, they have a centromere that is located towards the end of the chromosome. Thus, telocentric chromosomes have a 'rod' shaped appearance. In some cases, the telomeres extend from both the chromosome ends. The telocentric chromosome is not present in humans.

Nitric oxide has been implicated in initiating and inhibiting apoptosis through its possible action as a signal molecule of subsequent pathways that activates apoptosis

The protein molecules in the cell membrane receive signals from other cells or the outside environment and convert the signals to messages, that are passed to the organelles inside the cell.

Growth 1 phase is a very active period. In this period, the cell synthesizes vast range of proteins which includes the enzymes and structural proteins necessary for growth of the cell. In the G1 phase, the chromosome are made of single molecule of DNA, at this point in humans, the number of chromosomes per cell is 46 which is 2N and identical to the somatic cells.

The chromosomes continue to pull apart, but non-sister chromatids are still loosely associated via the chiasma. The chiasma begins to move toward the ends of the tetrad as separation continues. This process is known as terminalisation. Also during diakinesis, the nuclear envelope breaks down and the spindle fibers begin to interact with the tetrad.

Nucleus is a site for transcription in which messenger RNA (mRNA) are produced for protein synthesis.

It is the flattened membrane, which is mainly used to store the substances made by the cell. This membrane also helps in preserving and transporting materials within the cell. Hence, it is also called as the post office of a cell.

German scientist Karl Vogt was the first to describe the principle of apoptosis in 1842.

CDK5 is required for proper development of the brain. Cdk5 is involved in the processes of neuronal maturation and migration, phosphorylating the key intracellular adaptor of the reelin signaling chain.

Acentric chromosomes are those that lack centromeres, i.e. the centromere is totally absent on the chromosome. These chromosomes are observed due to effects of chromosome-breaking process like irradiation.