Stages of Meiosis

Life Without Meiosis…• True or false? Without meiosis, we would all be

identical clones of our parents.

What are homologous chromosomes?• Two different versions of the same chromosome.• One came from your mom, the other came from

your dad.• They are NOT identical. • Example: You have 2 different chromosome #4’s. You got

one from your mom and one from your dad. Both of these together are called “homologous chromosomes.”

Processing Piece:

• Draw a pair of homologous chromosomes. Label one of them “chromosome #4 from dad” and the other “chromosome #4 from mom.”

What are the stages of meiosis?1) Prophase 1: Chromosomes appear. But this time,

the homologous chromosomes are paired together. (These pairs are called “tetrads.”)

2) Prometaphase 1: Nuclear membrane disappears.3) Metaphase 1: Pairs of homologous chromosomes

line up in the middle of the cell.

Processing Piece:

• Illustrate the 1st 3 stages of meiosis.

What are the stages of meiosis?

4) Anaphase 1: Homologous chromosomes are pulled apart, so one whole chromosome goes to each new cell.5) Telophase 1: Two new cells form. Since each has only 1 set of chromosomes, they are haploid cells.

Processing Piece:

• Illustrate the next 2 stages of meiosis.

What are the stages of meiosis?6) Prophase II: Chromosomes appear.7) Prometaphase II: Nuclear membrane disappears.8) Metaphase II: Chromosomes line up in the middle.9) Anaphase II: Sister chromatids are pulled apart.10) Telophase II: Two new cells are formed from each cell that divided, resulting in a total of 4 haploid gamete cells.

Processing Piece:

• Illustrate the last 5 stages of meiosis.

Why are gametes genetically unique?• Since gametes only get one version of each

chromosome, the versions of chromosomes found in each haploid gamete will be different.

• Because gametes are unique (different), when they join together, they produce zygotes, and then adults, that are also unique – not identical clones.

Processing Piece:• Draw a diploid cell with two types of chromosomes

(so 4 chromosomes total). Label each: – Chromosome 1(dad) - Chromosome 1(mom)– Chromosome 2 (dad) - Chromosome 2(mom)

• Show every type of gamete that could be produced if this cell went through meiosis.

Exit Ticket

1. What are the stages of meiosis?2. Name at least 3 differences between mitosis

and meiosis.