Mitosis: A Meiosis In Diploid Cells

Chromosome pairs line up across the equator of the spindle at metaphase I (5). In anaphase I the chromosomes separate and travel to opposite ends of the spindle. The chromosomes migrate to the equators of two new spindles for metaphase 2 (7). Next the chromatids are pulled apart in anaphase 2 to form four clusters of chromosomes in telophase 2. The nuclear envelopes reform around four haploid nuclei that will give rise gamete

a) As before follow instructions in the handout and draw pictures for each stage of Meiosis I an Meiosis II – color!

Meiosis consists of one DNA replication and two nuclear divisions resulting in 4 daughter cells. The process which provides for genetic variation is crossing over. Crossing over occurs in the early stages when homologous chromosomes move together so that their chromatids form a tetrad. This is called synapsis and allows for the exchange of chromosome sections.

Mitosis: This is the process by which a cell duplicates the chromosomes in its cell nucleus in order to generate two identical daughter nuclei.

These bivalents line up along the equator during metaphase I, the arrangement of the bivalent is completely random and relative to the orientation of the other bivalents, this is known as the independent assortment of chromosomes. This is followed by anaphase I where the homologous chromosomes separate and move to the opposite poles of the cell. At telophase I the cell divides into two, each cell contains one chromosome from each homologous pair. The second stage of meiosis is similar to mitosis.

Meiosis is the cell cycle for germ cells (gametes) where they are haploid (n) so that is why they have two sets of phases.

A) Meiosis consists of two cell divisions and is broken up into Meiosis I and Meiosis II. At the beginning of the Cell Cycle, in this case there are four chromatids each from the homologous pairs being A, a, B, b. This is the Diploid number (4) meaning it is 2 times the haploid number that will be seen at the end of meiosis II. During the S phase of interphase, the chromatids replicate and reach the end of G2 phase. Now starting meiosis, during the first stage of prophase I the chromosomes condense and pair up through synapsis with their sister chromatids creating AA, aa, BB, bb. After they pair up they go through a process called crossing over, where the homologous chromosomes share a piece of their genetic material with each other. Crossing over allows for the genetic diversity of chromosomes. Now there are four homologous chromosomes Aa, Aa, Bb, Bb, each containing heterozygous alleles because the sister chromatids exchanged genetic information with their homologous pair. During late prophase I, spindle fibers being to form where they will later attach to a homologous chromosomes centromere. The next stage is Metaphase I. During metaphase I, the homologous pairs line up at the metaphase plate, also known to be the center of the cell. The homologous pairs form a tetrad which is considered a group of four homologous chromosomes. These homologous chromosomes orient themselves randomly, which is know as the process of independent

[A labelled diagram of the end of the Prophase stage of a cell here would be

Mitosis is one of two main methods of cell replication, the other being meiosis. It is “the simple duplication of a cell and all of its parts” resulting from the splitting of a cell. The ‘parent’ or original cell splits, duplicating its DNA (packaged in chromosomes) producing two ‘daughter’ or new cells with the same genetic code. There are four stages of mitosis; Prophase, Metaphase, Anaphase and Telophase. Interphase is not an official phase of mitosis as the cell is at ‘rest’ and not being divided during this phase. It is often called one of the phases of mitosis as it is one of the stages in the life cycle of a cell; however it is not a phase of mitosis due to the fact that no division takes place.

Response Feedback: Meiosis occurs only in replicating gametes or reproducing cells. In phase one, the number of chromosomes is reduced by half but the chromatid pairs remain together. In phase two, the chromatids split apart forming four daughter cells. Non-germ cells such as red blood cells or skin cells undergo mitosis.For more information on this topic, consult:Carol Mattson Porth and Glen Matfin, Pathophysiology, 8th Edition,

In this phase the spindles start to appear in their formation while the nuclear membrane starts to disappear. During prophase the cell prepares to divide. By tightly condensing its chromosomes and creating the spindle formation, called chromosome condensation. In prophase chromatin fibers condense into chromosomes this stage which are long, thin and thread-like. In this stage chromosomes have two chromatids, joined by a centromere. In metaphase, the centrosomes begin pulling the chromosomes towards the other side of the cell. The building of tension causes makes the chromosomes align along the metaphase plate or equatorial plane. Then they have to pass a checkpoint to move on to anaphase. The metaphase checkpoint makes sure that the kinetochores ( a protein structure on chromatids where spindle fibers are attached to ) are properly attached to the mitotic spindle and they check that the chromosomes are along the metaphase plate. Nearing the end of the process anaphase described to combine sister chromatids together, forming two identical daughter chromosomes. Later on in anaphase, chromosomes reach their condensation

Mitosis tried its best to break me. All the phases to remember and all the functions of the phases seriously couldn’t the human body be a little easier to comprehend. At first glance Mitosis seemed not so complicated until realising the intricacies of the process. I grasped the basic principle of mitosis in its simplest form, cells divide. The four phases prophase, metaphase, anaphase and telophase all had a part to play in cell division but what each phase contributed I could not understand. also over the whole cell cycle there was really a total of nine phases if you count the interphase, mitotic phase, G1 phase, G2 phase and S phase I needed some clarification. I endeavoured to find out answers to four questions to clarify and understand clearly.

Meiosis is the process in which the gamete cells turn from haploid to diploid. Meiosis involves eight stages: Prophase 1, Metaphase 1, Anaphase 1, Telophase 1, Prophase 2, Metaphase 2, Anaphase 2, and Telophase 2. Prophase 1 is when chromosomes cross over. The chromosomes exchange genetic information making new and distinct traits. Metaphase 1 is when the crossed-over

Telophase 2- This is where the process ends and meiosis is complete. A nuclear envelope forms around each set of chromosomes and then cytokinesis occurs, four daughter cells are then produced with a haploid set of chromosomes.

The main focus of this lab was to be able to understand the different phases of mitosis and the cell cycle and also identify what those stages may look like. Mitosis is the process in which concerns the production of new cells. For example, when apoptosis(cell death) the process of Mitosis begins to replace the dead cells. To be able to familiarize ourselves with this concept, we took a sample of an onion root and had it put through a process to be able to look at the different phases under the microscope. We found that the majority of the cells were mostly undergoing Interphase or Prophase which are the phases in charge of crossing over of DNA and where the chromosomes then become visible and the nuclear envelope dissipates. The conclusion of this lab was that Mitosis is essential for the production of new cells. In the case of the onion root sample, the cells were damaged leading to the tester to undergo Mitotic cell division and it was found that mainly Interphase and Prophase were the stages that occurred in this lab.