Meiosis and Sexual Reproduction No More Clones! Isn’t Love Grand?

Objectives “SEX”Understand the meaning of “SEX” Understand the process of meiosis Understand the need to undergo meiosis as sexual organisms – to produce change or variation

Need For Sex = Need for Change Sex: results in the new genetic combinations. Babies look different than parents New babies = new gene combinations Meiosis is key to enhancing this variation

Sex Terms to Know Diploid: having 2 sets of each chromosome type –You are a Diploid or 2N critter! Haploid: having 1 set of chromosome type –Egg / Sperm are Haploid Homologous chromosomes: – Daddy chromosome and Mommy chromosome –Each is a copy. You send either mommy or daddy chromosome into your sex cell (egg or sperm)

How they Match Up: Mitosis –produces 2 daughter cells –daughters are clones of the parent –daughter cells are diploid –growth, replacement, repair Meiosis –produces up to 4 daughter cells –daughters are distinct from parents –daughter cells are haploid –generation of gametes (sex cells): egg & sperm

Meiosis (the process) Meiosis: nuclear division with a reduction in chromosome number by half Goal: make 4 sex cells Process: 1.Double all DNA Chromosomes doubled 2.First Division 4N  2N 3.Second Division 2N  1N

Meiosis Overview Essentially, Double, then Divide Twice then Package 1N (set) of Chromosomes into Egg or Sperm Cell

Genetic Variation due to Eggs and Sperm Happening to Meet and Fall in Love Variation in the DNA of a zygote Random fertilization: 8 + million possible combinations of sperm and egg = 70,368,744,000,000 possible combinations

Variation #2 -- Choosing Mommy or Daddy Chromosome for Egg or Sperm Cell

Variation #3 Cross Over -- Mommy and Daddy Chromosomes Hold Hands and Swap Genes New chromosomes end up in the egg or sperm cells (4,951,760,200,000,000,000,000,000,000 different zygotes with a single crossover)

Meiosis Movie – get your Popcorn out

A Quicktime Movie