Reproduction 2 Types If both parents replicated cells

Reproduction!!! 2 Types

– If both parents replicated cells using mitosis, a child would receive 46 chromosomes from dad & 46 from mom given a grand total of…? – 92! (Way too many) – So…if dad could give 23 + 23 from mom = 46! (Bingo!)

Examples of Asexual!!!! � Binary Fission � Budding � Fragmentation

Better when the environment is not favorable or becomes unstable

Meiosis

Meiosis • Def: 2 successive cell divisions that produce gametes • What does that mean? – Successive one right after the other – Gametes a haploid reproductive cell, either an egg or a sperm – Haploid containing only 1 of every chromosomes (n) – Diploid containing 2 of every chromosome (2 n)

Some More Vocabulary • Body Cells – AKA somatic cells – Ex skins cells, nerve cells, blood cells – Diploid 46 chromosomes (23 pairs) pairs • Sex Cells – AKA germ cells – Ex egg & sperm – Haploid 23 chromosomes (all single) single Q: A mutation in which type of cell would be worse?

Chromosome Number in Mitosis

Meiosis = 2 Mitosis P 1 M 1 A 1 T 1 P 2 M 2 A 2 T 2 With a few slight differences!

Meiosis = 1 st Division Prophase I Prophase 1 Crossing Over Metaphase I Metaphase 1 chromosomes line up randomly 2 by 2 forming a tetrad (4 across) Anaphase 1 homologous chromosomes are pulled to opposite poles (sister chromatids do not separate!) Anaphase I Telophase I

Crossing Over

Prophase 2 Metaphase 2 Anaphase 2 Telophase 2 Single Chromosomes line Sister Chromatids are pulled apart up Meiosis II 2 nd Division

Mitosis vs. Meiosis � Cells divide twice! (Mitosis divide only once) � End result is 4 different cells instead of 2 genetically identical cells! � Chromosome number is cut in half! › 2 n (diploid) n (haploid) = Meiosis › 2 n = Mitosis � Crossing Over!

• The purpose of meiosis is…? • To produce gametes which are necessary for sexual reproduction. • Allows for new mixtures of combinations called genetic recombination • VARIATION!