Meiosis Production of Gametes Aka Sex Cells What
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Meiosis Production of Gametes Aka: Sex Cells
What is our normal Chromosome number? 46 What would happen if a sperm had 46 chromosomes and the egg had 46 chromosomes at fertilization? 46 + 46 = 92 That’s not human!! – Human’s chromosome # is 46! – Anything more or less is a mutation and may have drastic results How many chromosomes therefore should be in sperm and egg to keep the chromosome number at 46 when fertilization occurs? 23 in each sperm and egg
So how will we solve this problem of maintaining our normal chromosome number of 46 at fertilization? MEIOSIS!!! • Is a form of nuclear division that divides the chromosome number in half. • This process is vital for sexual reproduction. • Occurs in an organisms reproductive organs – Testes in males to produce sperm cells with 23 chromosomes in each – Ovaries in females to produce eggs with 23 chromosomes in each
Process of Meiosis • Occurs in two divisions and results in gametes (sex cells) each with half the normal chromosome number • Results in 4 genetically different cells each with half the normal chromosome number
Meiosis Originally 4 chromosomes in this cell Now there are 4 cells each with 2 chromosomes and they are genetically different
Gametogenesis Production of Gametes • Spermatogenesis – Following one round of meiosis, men will produce 4 genetically different sperm each with half the normal chromosome number So ladies, how would you like to have 4 babies at one time? • Oogenesis – Following one round of meiosis, women will produce 1 egg and 3 polar bodies which are all genetically different but with half the chromosome number. – The 3 polar bodies will break down and be reabsorbed
Spermatogenesis Oogenesis Three Polar bodies Egg Sperm
Difference between Mitosis and Meiosis Mitosis Meiosis Occurs in body cells Occurs in testes and ovaries Produces 2 genetically identical daughter cells Produces 4 genetically different sex cells Has only 1 division Has two divisions Involved in asexual reproduction Involved in sexual reproduction 2 n = 46 Chromosomes 1 n = 23 Chromosomes
