CSCOPE Unit 08 Lesson 02

MEIOSIS INTRODUCTION

What is a chromosome? A piece of coiled DNA

How many chromosomes do human cells have?

46 (in non-sex cells)

Do ALL humans have the same number of chromosomes in their cells?YES! (Except people with genetic

disorders causing extra chromosomes or

missing chromosomes)

Where did the 46 chromosomes come from?

CHROMOSOMES

If we get our chromosomes from our parent, why do we not have a total of 92 (46 from mom and 46 from dad)?

How does each parent manage to only give 23 chromosomes to their child?

TURN TO A FRIEND AND DISCUSS…

YOU were made from one cell from your mom and one cell from your dad. So, how is it the same? Shouldn’t you have double the number of chromosomes? No, the number is the same, because

the egg and sperm cells only have half the number of chromosomes, so when they combine they have the full 46.

SO, sex cells have how many chromosomes? 23 chromosomes

SO…

How are gametes (sex cells) formed, if they only have 23 chromosomes?Through a process called MEIOSIS

Meiosis is similar to Mitosis but has some differences.

SEX CELLS -- GAMETES

Four Phases: Interphase Prophase Metaphase (and) Telophase

DNA replication happens before

mitosis during the synthesis phase of the cell cycle.

MITOSIS — QUICK REVIEW

MITOSIS — QUICK REVIEW

Meiosis Animation #1

Meiosis Animation #2

MEIOSIS

Mitosis results in…Two IDENTICAL daughter cells—no genetic diversity

Meiosis results in…FOUR daughter cells—that are different from parent cells, resulting in genetic diversity

MITOSIS VS. MEIOSIS—PRIMARY DIFFERENCE