Meiosis introduction

Chromosomes What is a chromosome? How many chromosomes do A piece of coiled _______ How many chromosomes do human cells have? _____ (in non-sex cells) Do ALL humans have the same number of chromosomes in their cells? ______! (Except people with genetic disorders causing extra chromosomes or missing chromosomes) Where did the 46 chromosomes come from?

Turn to a friend and discuss… 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?

So… 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? ____, 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? ______ chromosomes

Sex Cells -- gametes How are gametes (sex cells) formed, if they only have 23 chromosomes? Through a process called _______ Meiosis is similar to mitosis but has some differences.

Mitosis — quick review Four Phases: DNA replication happens before Prophase Metaphase Anaphase Telophase DNA replication happens before mitosis during the synthesis phase of interphase.

Mitosis — quick review

Mitosis vs. meiosis—primary difference Mitosis results in… _______ IDENTICAL daughter cells—no genetic diversity Meiosis results in… __________ daughter cells—that are different from parent cells, resulting in genetic diversity