Meiosis Notes

How many chromosomes are in most of your body cells?

46 chromosomes

1. Notes

A bacterium has a single circular chromosome. When it reproduces, it creates a copy of its chromosome and then splits in two, resulting in two cells, each with a single identical chromosome. Humans have 46 chromosomes.

5. Notes

Also, meiosis exchanges some DNA sequences between chromosomes.

Both (Mieosis and Mitosis)

DNA replicates once Cytoplasm divides at the end Daughter cells are produced from one diploid parent cell

Mitosis

Daughter cells are identical to parent cells Involved in tissue repair

What are gametes? How many chromosomes are in gametes?

Gametes are sperm and egg cells. Both Sperm and Egg cells have 23 chromosomes in each gamete

Why do gametes not have 46 chromosomes?

Human sperm cells and egg cells have 23 chromosomes. Well if a sperm cell has 23 chromosomes and an egg cell has 23 chromosomes, when they come together that makes 46 chromosomes

7. Notes

In unicellular organisms, meiosis produces spores. In sexually reproducing multicellular organisms, meiosis produces specialized cells called gametes (sperm cells in males, egg cells in females). Meiosis involves a parent cell going through two cycles of cell division. In multicellular organisms, the male parent cell is a spermatocyte. The oocyte is the female parent cell. In both unicellular and multicellular organisms, the resulting cells contain only half the number of chromosomes of the parent cells.

Prophase 2

It's not going to be nearly as eventful as it was in Prophase 1 because they are not going to have homologous pairs They also are not going to have that amazing process called crossing over That doesn't happen again in Prophase 2 You have your chromosomes and the spindles starting to form like in prophase 1 but prophase 2 is not nearly as eventful of having that process of crossing over

10. Notes

Meiosis increases genetic diversity for natural selection to act upon.

11. Notes

Meiosis is the process of splitting a single diploid cell into four haploid cells.

6. Notes

Mitosis is a process by which many single-celled organisms reproduce. During mitosis, the cell replicates its genetic material. Mitosis ends once the cell has split into two cells. Cells of multicellular organisms undergo mitosis to replicate their existing cells for growth and repair. A multicellular organism starts life as a single cell.

4. Notes

Mitosis is a process of cell division by which one cell becomes two cells, identical to each other and identical to the original cell. Meiosis is a type of cell division that begins with a single cell and results in four cells rather than two.

What's the difference between Mitosis and Meiosis?

Mitosis makes identical body cells like your skin cells and stomach cells. Recall from this Mitosis clip since it makes identical body cells, Mitosis is important for growth and for repair of damage or to replace worn out cells. Meiosis is a process that contributes to genetic variety. Meiosis also doesn't make body cells. Meiosis makes sperm and egg cells; otherwise known as gametes, the fancier word.

12. Notes

Most cells in a sexually reproducing organism contain a full set of chromosomes, known as the diploid number. In humans, this number is 46 (23 pairs). Meiosis I produces two daughter cells with the haploid number of chromosomes.

8. Notes

Most cells in a sexually reproducing organism contain a full set of chromosomes, known as the diploid number. In humans, this number is 46 (23 pairs). Meiosis I produces two daughter cells with the haploid number of chromosomes.

Mitosis results in two identical cells. What does Meiosis result in? (How many new cells and are they identical?)

Now keep in mind that Meiosis in males produces sperm cells and in females, it produces egg cells. Because of independent assortment and also crossing over, you're going to have variety.

Telophase 2

Nuclei reform and the 2 cells are each going to divide so you can see here that 4 cells are going to be formed

Prophase 1

One thing I like to remember about prophase is "pro" this actually means "before" This is where the chromosomes are going to condense and thicken They are actually going to line up with their homologous pairs When these chromosomes are lined up in homologous pairs, they have a way that they can transfer their genetic information and exchange it between each other It makes for what we call Recombiant Chromosomes which can eventually contribute to the variety that we were mentioning that siblings can have ever when they have the same parents

Anaphase 2

Remember "A" for "Away", but this time it's the Chromatids that are getting pulled away by the spindle fibers Chromatids are getting pulled away to opposite sides of the cell

Metaphase 2

Remember think "M" for "Middle", the chromosomes are going to line up in the middle This time, though, they are in a single file line They are not in pairs like they were in Metaphase 1

3. Notes

Sexual reproduction involves merging two cells that each contributes half an organism's DNA. These cells fuse and produce a single cell. This cell divides many times, producing a new organism that has a mixture of genetic material from each parent cell. Each parent cell usually comes from two parent organisms. The offspring will therefore develop a blend of characteristics from both parents.

Telophase 1

Then, we end with Telophase 1, where you have "2" newly formed nuclei and it becomes obvious you will end Mieosis 1 with 2 new cells

Anaphase 1

Think "A" for "Away" because the chromosomes are going to be pulled away by the Spindle fibers

Metaphase 1

Think if the "M" as standing for "Middle" The chromosomes are going to be in the middle of the cell It's a little different, though, from mitosis because they're still going to be in pairs in the middle of the cell so it's not a single file line; they are in pairs in the middle

9. Notes

This swapping of genetic material takes place through a process called "crossing over." The point of crossing over is to produce new genetic variation. The genetic material is shuffled like a pack of cards.

Meiosis

Two divisions are needed Four haploid cells result Chromosomes mix during the division process Produces eukaryote gametes Provides genetic variation for natural selection

2. Notes

When single-celled organisms reproduce, they can do so relatively simply. When one cell replicates, its DNA is copied, and the cell divides into two new cells.