Are the daughter cells genetically identical to the parent cell in meiosis

Cancers result from inappropriate cell division. Most cell division is appropriate, however, and required for growth and reproduction of all organisms. The part of cell theory that states "all cells come from pre-existing cells" refers to cell division.

There are two basic types of cell division, called "mitosis" and "meiosis". Mitosis is the most common. It produces "daughter cells" that are genetically identical to the parent cell, except for mutations that may have occurred during division. Mitosis is the basis of growth and asexual reproduction. Meiosis differs from mitosis in that it produces gametes (eggs and sperm cells) for sexual reproduction. These cells are genetically different from the parent cell, for reasons we will discuss later.

1. Diploid and haploid

Before discussing meiosis further, it is essential to understand the concept of cell ploidy. In your cell nuclei, you have a total of 46 chromosomes but there are actually only 23 different kinds of human chromosomes. The 23 kinds of human chromosomes in your nuclei exist in pairs. During fusion of egg and sperm cells that became you, you received one set of the 23 human chromosomes from the egg and another set of the 23 human chromosomes from the sperm. Your cells are diploid, meaning that they have two sets of the 23 human chromosomes. This also means that you have two complete sets of human genes, one from your mother and one from your father. The chromosome pairs of each type are said to be homologous to each other. For example, in your cells the Chromosome 7 that you received from your mother is homologous to the Chromosome 7 you received from your father, and vice versa.

2. Mitosis

Some cells in your body are dividing and some are not. For example, cells in the deep layers of your skin or the lining of your mouth are continuously dividing to replace those lost to wear and tear. When you first came into existence as a zygote (fertilized egg), you were yourself a single cell. You grew into your present form by many cell divisions.

All of these cell divisions were by mitosis. It is a type of cell division in which the daughter cells are as genetically identical to the parent cell as possible. The central activity of mitosis is to carefully replicate all the genes of the cell and then be sure that each daughter cell gets a full and accurate set of them. Mitochondria, endomembrane components, ribosomes, etc. need not be so carefully divided. If each cell has a full and accurate set of genes, it can make more of anything it needs.

a. Stages of mitosis

The best way to start learning mitosis is to learn (memorize, draw, make poetry about) the sequence of events. The stages of mitosis are as follows:

Interphase - This is the relatively long period between cell divisions in which nothing obvious is happening, if the cell is viewed under the microscope. The most important event in this stage of mitosis is that chromosomes (where the genes are) are being carefully replicated by special enzymes. When replicated, the copies of each chromosome are attached together in the middle. Each replicate is called a "chromatid". During interphase, chromosomes are in their normal, dispersed condition. If you stain the cell for DNA and look at it under the microscope, the nucleus will be colored but you will not see individual chromosomes.

Prophase - In this phase, the chromosomes condense. They become coiled and wound up such that they are much shorter and fatter than normal (think of a very wound-up telephone cord).

During prophase, the cytoskeleton breaks down and its proteins begin to assemble into a special microtubule structure called the "mitotic spindle". This is the structure that will act to carefully divide the condensed chromatids between the two daughter cells so that each gets a full set of chromosomes.

A third event during prophase is the breakdown of the nuclear envelope.

Metaphase - During metaphase, the mitotic spindle is completed and connected to the chromatid pairs. The condensed pairs of chromatids line up in the center of the dividing cell, forming a distinctive band.

Anaphase - Anaphase is simple, though dramatic. During anaphase, chromatid pairs are pulled apart by the mitotic spindle and drawn to opposite poles of the dividing cell.

Telophase - During telophase, the dividing cell pinches together in the middle, randomly dividing cell components other than chromosomes between the two daughter cells. The divided chromosomes de-condense and nuclear envelopes form around them in the two cells. The cell re-ennters interphase.

Mitosis occurs in eukaryotes but not in prokaryotes. In prokaryotes, there is usually only one chromosome that exists in multiple copies. Prokaryotic cells simply pinch in the middle to divide and each daughter cell is nearly certain to get at least one copy of the single chromosome, which can then be copied if more are needed. Eukaryotes have multiple chromosomes and mitosis is required to assure that each daughter cell gets one (and only one) of each chromosome.

Prophase through telophase are just one part of what is known as the cell cycle. The cell cycle is essentially the life story of cells. It begins when the cell comes into existence by mitosis.

Following mitosis, the cell passes through the G1 phase of its life. During G1 of the cell cycle, much proteins synthesis occurs and the cell typically increases in size. G1 is followed by S, which is the phase of the cell cycle when chromosomes are replicated, yielding pairs of chromatids. G2 follows S. Further cell growth may occur during G2. After G2, mitosis (M) begins again.

In your body, many cell types have stopped dividing, e.g. brain or muscle cells. Their cell cycle has stopped in G1.

Are meiosis cells genetically identical?

Are the daughter cells genetically identical to each other in mitosis?