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Isabella Parenti #25
Alessandra Andion #02
María G Rojas #31
Valeria Mulas #23

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San Ignacio School

3rd D
Teacher: Arisnell Medina

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Meiosis has two stages, one and two.

1. Meiosis I: Pairs of chromosomes are lined up at the center of the cell and then pulled to each side. The crossing over which happens with the DNA, is an exchange of genes. The cell divides, leaving two new cells with a pair of chromosomes each.

2. Meiosis II: In Prophase II, the DNA that remains in the cell begins to condense and form short chromosomes. The centrioles also begin their journey to opposite sides of the cell. In Metaphase II all of the chromosomes line up along the center of the cell and the centrioles are in position for the duplication. Anaphase II, shows the chromosomes split and move to opposite sides of the cell, they split the DNA that exists.  And Telophase II, shows the DNA completely pulled to the sides and the cell membrane begins to pinch. The gametes will find other gametes with which they can combine. After that, they will form a new organism.

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Meiosis is a process that shuffles the cell's genes around. Is a process where a single cell divides twice to produce four cells containing half the original amount of genetic information. These cells are our sex cells ; sperm in males, eggs in females.

For more information you can see this page

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Meiosis is a process where a single cell divides twice to produce four cells containing half the original amount of genetic information. These cells are our sex cells - sperm in males, eggs in females.

During meiosis one cell divides twice to form four daughter cells.

These four daughter cells only have half the number of chromosomes of the parent cell - they are haploid.

Meiosis produces our sex cells or gametes (eggs in females and sperm in males).

Meiosis can be divided into nine stages. These are divided between the first time the cell divides (meiosis I) and the second time it divides (meiosis II):

Meiosis I
1. Interphase:

The DNA in the cell is copied resulting in two identical full sets of chromosomes.

Outside of the nucleus are two centrosomes, each containing a pair of centrioles, these structures are critical for the process of cell division.

During interphase, microtubules extend from these centrosomes.

2. Prophase I:

The copied chromosomes condense into X-shaped structures that can be easily seen under a microscope.

Each chromosome is composed of two sister chromatids containing identical genetic information.

The chromosomes pair up so that both copies of chromosome 1 are together, both copies of chromosome 2 are together, and so on.

The pairs of chromosomes may then exchange bits of DNA in a process called recombination or crossing over.

At the end of Prophase I the membrane around the nucleus in the cell dissolves away, releasing the chromosomes.

The meiotic spindle, consisting of microtubules and other proteins, extends across the cell between the centrioles.

3. Metaphase I:

The chromosome pairs line up next to each other along the centre (equator) of the cell.

The centrioles are now at opposites poles of the cell with the meiotic spindles extending from them.

The meiotic spindle fibres attach to one chromosome of each pair.

4. Anaphase I:

The pair of chromosomes are then pulled apart by the meiotic spindle, which pulls one chromosome to one pole of the cell and the other chromosome to the opposite pole.

In meiosis I the sister chromatids stay together. This is different to what happens in mitosis and meiosis II.

5. Telophase I and cytokinesis:

The chromosomes complete their move to the opposite poles of the cell.

At each pole of the cell a full set of chromosomes gather together.

A membrane forms around each set of chromosomes to create two new nuclei.

The single cell then pinches in the middle to form two separate daughter cells each containing a full set of chromosomes within a nucleus. This process is known as cytokinesis.

Meiosis II
6. Prophase II:

Now there are two daughter cells, each with 23 chromosomes (23 pairs of chromatids).

In each of the two daughter cells the chromosomes condense again into visible X-shaped structures that can be easily seen under a microscope.

The membrane around the nucleus in each daughter cell dissolves away releasing the chromosomes.

The centrioles duplicate.

The meiotic spindle forms again.

7. Metaphase II:

In each of the two daughter cells the chromosomes (pair of sister chromatids) line up end-to-end along the equator of the cell.

The centrioles are now at opposites poles in each of the daughter cells.

Meiotic spindle fibres at each pole of the cell attach to each of the sister chromatids.

8. Anaphase II:

The sister chromatids are then pulled to opposite poles due to the action of the meiotic spindle.

The separated chromatids are now individual chromosomes.

9. Telophase II and cytokinesis:

The chromosomes complete their move to the opposite poles of the cell.

At each pole of the cell a full set of chromosomes gather together.

A membrane forms around each set of chromosomes to create two new cell nuclei.

This is the last phase of meiosis, however cell division is not complete without another round of cytokinesis.

Once cytokinesis is complete there are four granddaughter cells, each with half a set of chromosomes (haploid):

in males, these four cells are all sperm cells

in females, one of the cells is an egg cell while the other three are polar bodies (small cells that do not develop into eggs).

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Meiosis is a process where a single cell divides twice to produce four cells containing half the original amount of genetic information. These cells are our sex cells - sperm in males, eggs in females. During meiosis one cell divides twice to form four daughter cells.

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Mitosis have five phases:

1. In the Prophase, you need to duplicate DNA, get certain pieces in the right position, and generally prepare the cell for the process of mitotic division.

2. In the Metaphase, the DNA lines up along a central axis and the centrioles send out specialized tubules that connect to the DNA that has now condensed into chromosomes.

3. In the Anaphase, half of the chromosomes are pulled to one side of the cell and half go the other way.

4. In the Telophase, its time when the cell membrane closes in  and splits the cell into two pieces.

5. And the last phase; the Interphase, its the resting state. Its just going about its daily business of surviving and making sure it has all of the nutrients and energy it needs. It is also getting ready for another division that will happen one day.

If you want to learn more about the Mitosis you can watch this video

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Mitosis is the simple duplication of a cell and all of its parts. It duplicates its DNA. And one cell gives rise to two genetically identical daughter cells.

If you want to learn more about the Mitosis you can watch this video.

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Mitosis - Stages of Mitosis | Cells | Biology | FuseSchool

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Gregor Mendel, was a monk that through his work on pea plants, discovered the fundamental laws of inheritance. He deduced that genes come in pairs and are inherited as distinct units, one from each parent. Mendel tracked the segregation of parental genes and their appearance in the offspring as dominant or recessive traits. He created The Law of Segregation, The Law of Independent Assortment and The Law of Dominance.

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Chromosomes are tiny structures inside cells made from DNA and protein. The information inside chromosomes acts like a recipe that tells cells how to function and replicate. Every form of life has its own unique set of instructions.
The chromosomes describe what color eyes you have, how tall you are, and whether you're a boy or a girl.

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A gene is a specific segment of a DNA molecule that holds the information for one specific protein. DNA molecules have a unique code for each gene which codes for their specific protein. Some organisms can have more than 100,000 different genes so they will have 100,000 unique sequences of DNA ‘code’.
Genes are the basic unit of heredity. The genes of an individual are determined by their parent or parents.

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To ‘read’ these blueprints, the double-helical DNA is unzipped to expose the individual strands and an enzyme translates them into a mobile, intermediate message, called ribonucleic acid or RNA. This intermediate message is called messenger RNA (mRNA), and it carries the instructions for making proteins.

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Genetics its built around molecules called DNA.
Deoxyribonucleic acid or DNA, contains our genetic code, the blueprint of life. This essential molecule is the foundation for the “central dogma of biology”, or the sequence of events necessary for life to function. DNA is a long, double-stranded molecule made up of bases, located in the cell’s nucleus.

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Genetics is a field of biology that studies how traits are passed from parents to their offspring. The passing of traits from parents to offspring is known as heredity, therefore, genetics is the study of heredity.