Meiosis

Babies develop from zygotes… but where do zygotes come from?

Where do zygotes come from?• A zygote forms when a sperm cell and an egg

cell join together. • This process is called fertilization.

Processing Piece:

• Normal human cells each have 46 chromosomes. Human zygotes also have 46 chromosomes.

• If a human zygote has 46 chromosomes, how many chromosomes do you think are in the gamete cells?

(Hint: What + what = 46?)

What are haploid cells and diploid cells?• Haploid cells: cells with only one set of

chromosomes. “n” is used to represent haploid.• Diploid cells: cells with 2 sets of chromosomes.

“2n” is used to represent diploid.

Processing Piece:• Fruit flies have 4 different types of chromosomes.

(They’re called chromosome #1, chromosome #2, etc.)

• Draw a picture to illustrate what a haploid fly cell and a diploid fly cell would look like. Label them “haploid” and “diploid.” Label one “n” and the other “2n.”

What are gamete cells?

• Normal cells; everything that’s not a gamete.• In humans and most other animals, they are diploid.

What are somatic cells?

• Sex cells; male sperm cells and female egg cells• They are ALWAYS haploid.

Processing Piece:• Look at the drawings you made for haploid and diploid

cells. Label one “gamete” and the other “somatic.”• Why is it important for gametes to be haploid? What would

happen if gametes were diploid?

What is meiosis?• When a diploid somatic cell divides twice to produce 4

haploid gamete cells.• The 4 gametes are genetically unique (different). They

are different from the original cell and from each other.

Processing Piece:

• Draw a picture to illustrate the difference between mitosis and meiosis.

(Remember, mitosis is when a cell divides once to produce 2 identical daughter cells.)

What’s one memory trick for remembering the difference between mitosis and meiosis?

• Mitosis = “My Toe Grows” This is when cells divide to produce 2 identical daughter cells. This is how your body grows.

Also, remember “t” for TWO new cells produced.• Meiosis = “My, oh my, we’re talking about sex cells.”

Meiosis produces 4 different gametes (sex cells).• Another trick (I did not make this up):

Think “gametes” = “game time” to remember that gametes are sex cells.

Processing Piece:

• Make a T chart to contrast mitosis and meiosis. Come up with at least 2 differences.

Instructions for Card Sort

1. Sort the cards into to groups: Mitosis and Meiosis2. Raise your hand when you’re done so I can check.3. After I check it, copy the information onto your

page.4. Have a seat and start working on your independent

practice.

Exit Ticket1) How many cells does meiosis produce?2) Are the cells produced by meiosis…

a. Identical or genetically unique?b. Haploid or diploid?c. Gametes are somatic cells?

3) Why is it important that gametes only have 1 set of chromosomes instead of 2?