Do-Now Friday 4/29

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Answer explanation

A normal human cell has 46 chromosomes. This is the 2n, or diploid, number.

Gametes are haploid. This means they have only half the diploid number of chromosomes.

Half of 46 is 23.

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Answer explanation

Remember: Crossing over and independent assortment both increase genetic diversity.

They help make sure each gamete has unique DNA.

Which of these occurs just before the cell enters the G2 phase of the cell cycle?

• The nuclear membrane disentegrates

• Centrioles form

• The cell divides

• The cell replicates its DNA

Cells pass through a G2 checkpoint before entering mitosis. If DNA damage is detected, the cell does not enter mitosis until the damage is repaired. Why is DNA damage repaired before it goes into Mitosis?

• So another round of DNA synthesis does not have to take place

• So the cytoplasm can be divided equally between daughter cells during cytokinesis

• So the chromosomes can align at the metaphase plate during mitosis

• So healthy daughter cells are produced, and the organism can continue to grow