What is interphase? The term is derived from the Latin word "inter", translated as "between", and the Greek "phaseis" - period. This is the most important period during which the cell grows and stores nutrients in preparation for the next division. Interphase occupies most of the entire cell cycle, up to 90% of the entire cell life falls on it.
What is interphase
As a rule, the main part of the cell components grows over the entire phase, so it’s rather difficult to isolate any separate stages in it. Nevertheless, biologists divided the interphase into three parts, focusing on the replication time of deoxyribonucleic acid (DNA) in the cell nucleus.
Periods of interphase: phase G (1), phase S, phase G (2). The presynthetic period (G1), the name of which comes from the English gap, translated as “interval”, begins immediately after the division. This is a very long period, lasting from ten hours to several days. It is during it that the accumulation of substances and preparation for the doubling of genetic material takes place: RNA synthesis begins, the necessary proteins are formed.
What is interphase in its last period? In the presynthetic phase, the number of ribosomes increases, the surface area of the rough endoplasmic reticulum increases, and new mitochondria appear. A cell, consuming a lot of energy, is growing rapidly.
Differentiated cells, no longer able to divide, are in a resting phase called G0.
The main period of interphase
Regardless of what processes occur in the cell during interphase, each of the subphases is important for general preparation for mitosis. However, the synthetic period can be called a turning point, because it is during it that the chromosomes double and the direct preparation for division begins. RNA continues to be synthesized, but immediately binds to chromosome proteins, starting DNA replication.
The cell interphase in this part lasts from six to ten hours. As a result, each of the chromosomes doubles and already consists of a pair of sister chromatids, which then disperse at the poles of the fission spindle. In the synthetic phase, centrioles double, if they are, of course, present in the cell. During this period, chromosomes can be seen through a microscope.
Third period
Genetically, chromatids are exactly the same, since one of them is maternal, and the second is replicated using messenger RNA.
As soon as the complete doubling of all genetic material has occurred, the post-synthetic period preceding the division begins. This is followed by the formation of microtubules, from which a spindle of division will subsequently be formed, and chromatids will diverge at the poles. Energy is also stored, because during the period of mitosis, the synthesis of nutrients decreases. The duration of the postsynthetic period is short, usually only a few hours.
Control points
During the cell cycle, the cell must go through a kind of control points - important "marks", after which it passes to another stage. If for some reason the cell could not pass the control point, then the entire cell cycle freezes, and the next phase does not begin until the problems that prevented it from passing through the control point are eliminated.
There are four main points, most of which are just in interphase. The first checkpoint the cell passes in the presynthetic phase when DNA intact is being tested. If everything is correct, then the synthetic period begins. In it, the reconciliation point is a check of accuracy in DNA replication. A checkpoint in the postsynthetic phase is a check for damage or omissions at the two previous points. This phase also checks how fully replication and cells have occurred. Those who fail this test are not allowed to mitosis.
Interphase problems
Violation of the normal cell cycle can lead not only to malfunctions in mitosis, but also to the formation of solid tumors. Moreover, this is one of the main reasons for their appearance. The normal course of each phase, however short, determines the successful completion of subsequent stages and the absence of problems. Tumor cells have changes at the milestones of the cell cycle.
For example, a synthetic period of interphase does not occur in a cell with damaged DNA. Mutations occur that result in loss or changes in the p53 protein genes. Blockade of the cell cycle does not occur in the cells, and mitosis begins ahead of schedule. The result of such malfunctions is a large number of mutant cells, most of which are not viable. However, those that can function give rise to malignant cells that can divide very quickly due to the reduction or absence of a resting phase. The characterization of interphase contributes to the fact that malignant tumors consisting of mutant cells have the ability to divide so rapidly.
Interphase duration
Here are some examples of how much longer the interphase period takes in a cell’s life compared to mitosis. In the epithelium of the small intestine of ordinary mice, the "resting phase" takes at least twelve hours, and mitosis lasts from 30 minutes to an hour. The cells that make up the root of horse beans divide every 25 hours, with the phase M (mitosis) lasting about half an hour.
What is interphase for cell activity? This is the most important period, without which not only mitosis, but also cellular vital activity as a whole would be impossible.