Prezi

http://prezi.com/ivv1zl6t6mbj/meiosis/

Creators

Nicolas Marin
Cristina Maldonado
Jose Garcia
Enrique Asmar
8th Yelllow

Animations and Videos

                                                    Animation with the Stages of Meiosis

Sources

Due to the fact that we are not scientist or teachers , but students , we have taken information from the internet from the following web pages :

• Wikipedia.com
• Buzzle.com

Comparing Meiosis and Mitosis

The main differences are that :

The chromosomes in meiosis undergo a recombination which shuffles the genes producing a different genetic combination in each gamete, compared with the co-existence of each of the two separate pairs of each chromosome (one received from each parent) in each cell which results from mitosis.

The outcome of meiosis is four (genetically unique) haploid cells, compared with the two (genetically identical) diploid cells produced from mitosis.

Sr.No	Mitosis	Meiosis
1.	Mitosis takes place within somatic cells (cells that make up the body).	Meiosis takes place within gamete cells (sex cells).
2.	One single division of the mother cell results in two daughter cells.	Two divisions of the mother cell result in four meiotic products or haploid gametes.
3.	A mitotic mother cell can either be haploid or diploid.	A meiotic mother cell is always diploid.
4.	The number of chromosomes per nucleus remains the same after division.	The meiotic products contain a haploid (n) number of chromosomes in contrast to the (2n) number of chromosomes in mother cell.
5.	It is preceded by a S-phase in which the amount of DNA is duplicated.	In meiosis, only meiosis I is preceded by a S-phase.
6.	In mitosis, there is no pairing of homologous chromosomes.	During prophase I, complete pairing of all homologous chromosomes takes place.
7.	There is no exchange of DNA (crossing-over) between chromosomes.	There is at least one crossing-over or DNA exchange per homologous pair of chromosomes.
8.	The centromeres split during anaphase.	The centromeres do separate during anaphase II, but not during anaphase I.
9.	The genotype of the daughter cells is identical to that of the mother cells.	Meiotic products differ in their genotype from the mother cell.
10.	After mitosis, each daughter cell has exactly same DNA strands.	After meiosis, each daughter cell has only half of the DNA strands

What is Meiosis?

Meiosis is a special type of cell division necessary for sexual reproduction in eukaryotes. The cells produced by meiosis are gametes or spores. In many organisms, including all animals and land plants, gametes are called sperm and egg cells.
Meiosis begins with one diploid cell containing two copies of each chromosome,one from the organism's mother and one from its father,-and produces four haploid cells containing one copy of each chromosome. Each of the resulting chromosomes in the gamete cells is a unique mixture of maternal and paternal DNA, resulting in offspring that are genetically distinct from either parent. This gives rise to genetic diversity in sexually reproducing populations. This genetic diversity can provide the variation of physical and behavioural attributes upon which natural selection can act, but, as described below in Section 6, Origin and function of meiosis, the genetic diversity may be largely a by-product of the homologous recombination that is primarily employed for its DNA repair function during meiosis.

Diagram of the stages of meiosis: two stage division of a cell, producing gametes and halving the number of chromosomes in its nucleus.
Prophase I: first phase of meiosis.
Metaphase I: second phase of meiosis.
Anaphase I: third phase of meiosis.
Telophase I: fourth phase of meiosis.
Prophase II: fifth phase of meiosis.
Metaphase II: sixth phase of meiosis.
Anaphase II: seventh phase of meiosis.
Telophase II: eight phase of meiosis.
Four cells: last phase of meiosis.

What is Mitosis?

Mitosis is the process by which a eukaryotic cell separates the chromosomes in its cell nuclei into two identical sets, in two separate nuclei.

Mitosis occurs only in eukaryotic cells and the process varies in different species.   The process of mitosis is fast and highly complex. The sequence of events is divided into stages corresponding to the completion of one set of activities and the start of the next. These stages are interphase, prophase,prometaphase, metaphase, anaphase,

and telophase.The following image shows the stages of Interphase and Mitosis.

During mitosis the pairs of chromatids condense and attach to fibers that pull the sister chromatids to opposite sides of the cell. The cell then divides incytokenesis, to produce two identical daughter cells which are still diploid cells.