c. The creation of genetic variety by crossing over between homologous chromosomes During prophase 1 of meiosis, equal portions of homologous chromosomes may be swapped. In this way new genetic combinations are made and linked genes separated. The variety which meiosis brings vital for to the process of evolution. By providing a varied stock of individuals it allows the natural selection of those best suited to the existing conditions and makes sure that species constantly change and adapt when these conditions change. This is the main biological significance of meiosis.
Instead of lining up on a metaphase, as in mitosis, chromosomes come together in pairs (2). Each chromosome in a pair is similar in structure (homologous), but would have come originally from different parents. Later in propha... ... middle of paper ... ...hese daughter chromosomes then begin to separate from each other, each moving away from the metaphase plate and toward one of the two spindle pole regions. The mechanisms that control chromosome separation clearly involve the interactions between microtubules and components in or near the kinetochore. Sometime after anaphase onset, the chromosomes have moved close to the spindle pole regions, and the spindle middle begins to clear.
This helps to create genetic diversity. Anaphase 1 is where the bivalents separate and the homologous chromosomes move to opposite poles of the cell. Telophase 1 is where the nuclear envelope reforms after disintegrating in prophase 1. Then cytokinesis is where the cell divides to create two new cells which are haploid (GENIE, 2010). The next main stage is meiosis 2 and this is where each chromosome is split into 2 sister chromatids.
To replicate, the cell goes through cell division. That is also known as mitosis. That is when one parent cell produces two daughter cells. Imagine, what would Earth be without DNA?
Mitosis and meiosis both occur in the M phase of the cell cycle, and are the methods of cell division to form somatic cells and gametes, respectively. They are both complex processes that form more than one daughter cell from one parent cell, and they have many similarities and differences, which will be discussed in this essay. Mitosis is the type of cell division that occurs in all somatic cells. Its purpose is to produce two genetically identical daughter cells. Before the process of mitosis starts, DNA replicates and the resulting sister chromatids are held together by cohesin proteins.
This form of recombination is called crossing-over. When the chromosomes glue themselves back together and separate, each has picked up new genetic material from the other. The constellation of physical characteristics it determines is now different than before crossing-over. In Meiosis 1, chromosomes in a diploid cell resegregate, producing four haploid daughter cells. It is this step in Meiosis that generates genetic diversity.Meiosis 2 is similar to mitosis.
This entire process is better known as the gene expression. On a DNA molecule, each gene directs the synthesis of a special type of RNA called messenger RNA. This mRNA molecule works in conjunction with the cell’s protein synthesizing mechanisms to direct the production of a polypeptide chain, which ultimately results in the formation of a protein. Protein synthesis occurs on the ribosomes. However, DNA is found in the nucleus.
Meiosis unlike mitosis has two cell divisions, Meiosis I and Meiosis II. In prophase I of meiosis I, the chromosomes begin by pairing with its homolog and this is also where crossing over occurs. In this stage just like prophase in mitosis the nuclear envelope breaks down and the mitotic spindle begins to develop as well. In Metaphase I the homologue chromosomes line up at the metaphase plate and the kinetochore microtubules attach to both ends of the chromosome. In anaphase I the homologs move to opposite ends of the poles and the homologs also begin to separate as well.
Realize that eukaryotes require the activity of telomerase to complete the synthesis of their linear chromosomes. The Semiconservative Nature of DNA Replication One property of the genetic material necessary for its function is the ability to replicate (reproduce) itself. After it was established that DNA is the genetic material, attention turned toward how DNA was replicating in living organisms. The Watson-Crick model of DNA structure (as outlined in the module on nucleic acids) suggested a possible mechanism for replication of DNA molecules. The nature of base pairing meant that if the two strands of a DNA molecule were separated, they could each serve as a template for the creation of a complementary strand by bringing in individual nucleotides to base pair with their complementary base on the template, and joining the new nucleotides together.
Meioses produces haploid daughter cells that are genetically different from each other and from the parent cell. However, mitosis is a form of cell division that produces daughter cells identical to the parent during repair or growth. Each cell contains the same genetic code as the parent cell, it is able to do this because it has copied it’s own chromosomes prior to cell division. Meiosis consists of two divisions whilst mitosis is followed in one division; both these processes involve the stages of interphase, prophase, metaphase, anaphase and telophase. Meiosis allows cell variation and genetic differences between each cell whereas mitosis is an exact replication of each cell.