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.
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.
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.
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.
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