January 17th 2017 archive

How do Cells Multiply?

Sexual and asexual reproduction:
Sexual reproduction is a form of reproduction that requires a male sex cell (sprem) and a female sex cell (egg) that are referred to as gametes. These cells are formed in ovaries for women, and the testies for men. When a male gamate and a female gamate are joined this is called fusion, this is how fertilization works. That is why this stage of sexual reproduction is called fusion, since the gamates are fused together. Gamates are also haploid  which means that there is only one set of chromosomes, therefor making the zygote diaploid, which means that there are two sets of chromosomes, since it is getting both chromosomes from the mother and the father. Gamates are formed by the process of meiosis.


There are two main cell forming processes. Mitosis and meiosis. There are four stages of mitosis, Prophase, Metaphase, Anaphase and Telophase. Each stage of mitosis is a different role in the process of cell division. Prophase is the first stage of mitosis, and during Prophase, there are two duplicated chromosomes, called “Daughter Cells”, these two chromatids come from already formed cells called thier “Parent Cell’s”. The daughter cells, are identical replicas of each other. They are not yet considered individual cells, because they are still attached together by the centromere. During prophase, the nuclear membrane begins to form, chromatin will condense (chromatin is the DNA, protiens and nutrients, that are in the nucleas, making it possible to see the chromosomes begin to form). Chromosomes are formed from a single piece of a DNA. Chromosomes replicate to create more identical copies of themselves, and these are called “sister chromatids”. After this, spindle fibres begin to form, these are long pieces of protein that have a tube or straw like body, that are going to be responsable for the seperation of the two daughter cells.

The next stage of mitosis is Metaphase, during this stage, the DNA from the parent cells is transferred to the daughter cells. The chromosomes will allign themselves into the middle the cell. The sister chromatids will remain at the centromere of the cell, because that is where they were in Prophase. The third stage of Mitosis is Anaphase. In this stage all the chromosomes are split into two by the spindle fibres, creating there to be two working chromosomes for each one there was in Metaphase and Prophase. There are two chromosomes at each poles (ends) of the daughter cells, and the spindle fibres are attached to those chromosomes. At the same time as this is happenening to the chromosomes, the daughter cells are unattached at the centromeres. Spindle fibres will then pull all of the chromosomes on each cell to the poles of thier cell.


The final stage of mitosis is Telophase. During this stage, the nuclear membrane will form around each of the cells chromosomes, to seperate them from the cells DNA from the cells cytoplasm (Cytoplam is the fluid that fills the cell). The cells chromatids will also begin to uncondense, making the cells less dense and diffuse.

One of the main differences between mitosis and meiosis, is that meiosis produces gamates (sex cells), while mitosis produces new cells.

The process of meiosis is similar to the process of mitosis, as it had similar stages, with, Prophase I, Metaphase I, Anaphase I, Telophase I, Prophase II, Metaphase II, Anaphase II, and Telophase II. During Prophase I, two chromosomes will pair and share DNA with each other, create what are called recombinant chromosomes, chromosomes also begin to from closer together, to create chromosomes consiting of four chromatids (also know as bivalents). During Metaphase I, the chromosones line up in a double row along the metaphase plate (a line of spindle fibres that divide the cell). While the pairs of chromosomes are randomly lined up around the metaphase plate.

During Anaphase I, the bivalent chromosomes seperate to opposite ends of the poles of the cell. During Telophase I, the cells become less dense and diffuse, and the nuclear membrane is reformed. Meiosis II is different for both males and females, since they both have different sex cells. The folllowing charts will help explain meiosis II in both males and females.


There are a few differences between mitosis and meiosis. As I previously mentioned, mitosis is new cell creation, and mieosis is sex cell creation. Meiosis has two rounds of seperation and cell division, while mitosis only has one. During mitosis the daughter cells are identical to the parent cells as well as each other, but during meiosis, the daughter are not identical to thier parent cells, nor to each other.

In human reproduction, every gamete contains exactly 23 chromosomes each. So when the two sex cells fuse together they become a zygote. Which is what the embryo is, as it will contain the 23 chromosomes from each sex cell, giving the zygote a total of 46 chromosomes. Exactly half of these chromosomes are from the mother and half are from the father. The zygote is diaploid, which means that there are two sets of chromosomes, since it is getting both chromosomes from the mother are father (two gamates that are haploids). The fetal development will then begin, in three trimesters, each for three months each.


In the first trimestre of growth, the fetus will start developping orgam systems, (fingers, toes, eyes, brain, spinle chord.), and the sex of the fetus will be determined within one month after the first trimester. During the second trimester, the fetus’s eyes will open, the ears become larger, the carrier will be able to feel the fetus move around, and if the fetus has to be removed from the body, it will be able to be safley removed, and still be capable of surviving and living outside the body. In the third and final trimestre, the fetus will have rapid weight gain, and grow, to be prepared for its birthing.

Asexual Reproduction, is a form of reproduction that uses only one organism. As a result of only having one parent organism, the offspring of that organism are exactly the same genetically as thier parent, so that would make them clones or each other. Asexual reproduction, can take place in plants, animals, . It is different for every type of plant that uses asexual reproduction, for some, they form underground food organs that store it, to help create the next plant and care for it. For others, they create lateral buds (similar to a seed from a tree), some plsnts will also have long branches with plantlets (small seperate plants) growing on them, and others form runners with plantlets on them (like strawberries, for example).

In animals, assexual reproduction, generally only happens in certain animals, such as sea anenmie, starfish, and generally in bacteria (microorganisms). Aniamls can asexually reproduce through four different types of asexual reproduction: Fission, Budding, Fragmentation, or Parthengoneisis. Binary Fission, is when a cell divides into two cells to create two daughter cells. In Fisson, the cell and split into two to create two individual organisms. Or, it can split into two again from the indivdual cell, creating another two individual cells. Most sea animals (starfish, sea anenemies, coral) will asexually reproduce through this method. Budding, is the overgrowth of a cell, splitting it into two individual cells. This type of asexual reproduction is usually used within coral. Fragmentation is when the body breaks into two halfs, this process generally only occurs in starfish. Parthengonesis is when an egg becomes fully develpooed without fertilization. This will generally occur in bees, and species like them.


One of the main differences between sexual reproduction and asexual reproduction is that reprodution is thereproduction between two cells, while asexual reproduction is the reproduction is the reprodution within one organism. But some of the advantages and disadvantages between sexual and asexual reproduction are that during asexual reproduction, is that during asexual reproduction, it requires less time and less energy than sexual reproduction, but there is also no variation during asexual reprodution, so if the one parent cell is sick or has a desease, then the rest of its offspring will have that desease and could kill them all. But, during sexual reproduction, there is more variation within the organisms (not all the same, could not all get sick from the same desease), and the organism is more protected during sexual reproduction. But sexual reproduction requires two mates, as well as more energy to complete sexual reproduction.