Check the summary note below, it will be of help.
Explanation: Cell Reproduction
Cell reproduction is the process by which cells divide to form new cells. Each time a cell divides, it makes a copy of all of its chromosomes, which are tightly coiled strands of DNA, the genetic material that holds the instructions for all life, and sends an identical copy to the new cell that is created. This is a process called Mitosis, and can be found in greater detail by following the link.
Humans have 46 Chromosomes within each of their body cells. Other species have different numbers of Chromosomes, however. One species of fern has 1262 of them! As you might guess, the number of chromosomes does not directly impact the complexity of an organism. As chromosomes vary in size, one human chromosome can hold genetic information equivalent to the amount of genetic information in many chromosomes from another organism.
A chromosomes consists of two halves, called Chromatids. These halves are divided in their center by a centromere. This structure is what attaches to spindle fibers during mitosis to pull one chromatid to each side of the cell when it divides.
In humans, 44 of the chromosomes consist of autosomes, and the remaining two are the sex chromosomes. These chromosomes determine the gender of the organism. (A male has an X and a Y, while a female has to Xs).
In addition, all the chromosomes in an organism excluding the sex chromosomes are part of a homologous pair. They contain genes to control the same traits but the genes do not have the same instructions. For example, one chromosome might have the genes for brown eyes while its homolouge might have genes for blue eyes. One homolouge is inherited from the mother while the other is inherited from the father.
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The Cell Cycle
The cell cycle is the of steps that cells take to grow, develop, and reproduce. It can be broken down into five steps:
G1 Phase
S Phase
G2 Phase
M Phase
Cytokinesis
G1 Phase
During the G1 Phase, the cell grows and stores up energy that it will use during cell division. Nutrients are taken in and all the usual cell processes take place. Once cells are fully grown, they proceed on to the S Phase.
S Phase
During the S Phase, the DNA in the cell's nucleus is copied. This means that the cell then attains two copies of all the necessary DNA for normal cell activity, leaving a full set to be transferred into the new cell that will be created after the cell divides.
G2 Phase
During this phase, the cell prepares for cell division. This phase represents a time gap between the time when the cell copies its DNA and when it divides.
M Phase
During this phase, cell division takes place through Mitosis.
Cytokinesis
During Cytokinesis, the cytoplasm in the cell divides and the cell's membrane pinches inward and the cell begins to divide. Also, when plant cells divide, a cell plate forms between the two new cells to divide them. After this step, the new cell and sometimes the original cell also restart the cell cycle by beginning G1 Phase again. However, sometimes cells enter G0 phase, which is a phase where cells exit the cell cycle after they are fully grown and continue to serve their purpose in an organism.
Other Methods of Cell Reprocuction
Several other methods of cell reproduction exist. These include meiosis and binary fission. During binary fission, bacterial cells divide asexually. Meiosis, which is explained in further detail by following the link above, is used to change diploid body cells into haploid reproductive cells.
Binary Fission
Bacterial cells reproduce through a process called binary fission. During this process, bacterial cells reproduce by budding new genetically identical organisms from portions of their bodies. Asexual reproduction is a disadvantage to mitosis because it negates the positive effects of genetic variation and recombination.
Mitosis
Mitosis is one of biology's more complex processes and the process that is responsible for cell division in humans and all eukaryotes.
Mitosis is broken down into four phases: Prophase, Metaphase, Anaphase, and Telophase. Below, I will explain in detail what happens during each of these phases.
During mitosis, one cell divides itself to produce two daughter cells. Each of these cells are genetically identical to each other and so contain the same DNA.
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Steps of Mitosis
There are four separate steps of Mitosis:
Prophase.
Metaphase.
Anaphase.
Telophase.
This has the effect of creating identical cells to each new cell after each iteration of mitosis.
See picture below!!!
Meiosis
Meiosis is the process by which a regular diploid body cell divides and becomes 4 haploid gametes. It consists of two stages: Meiosis I and Meiosis II. Meiosis I is the first division of cells and Meiosis II is the second. This process is generally similar to regular Mitosis with a few differences that effect the end products.
See picture below!!!
