Meiosis Biology

Human Chromosomes Every normal human cell has, 23 pairs of chromosomes Total chromosomes = 46 22 pairs contain genes that code for normal, human traits Ex: eye color Chromosomes # 1-22 1 sex chromosome pair Chromosomes that determine sex Females = XX, Males = XY Chromosome # 23

Meiosis is: A process in the body that makes sperm and egg

In Meiosis: Crossing over occurs Exchange of information when homologous chromosomes cross each other Results in an increase of diversity- chromosomes are now mixed

Review: Mitosis End with the same number of chromosomes as the original cell One cell divides into 2 identical “daughter” cells Occurs in body cells Ending cells have pairs of chromosomes For growth, repair and to replace cells

What is meiosis? End with half the number of chromosomes as the original cell One cell divides two times into 4 “daughter” cells Occurs in reproductive cells of an organism Ending cells do not have pairs of chromosomes For the production of gametes (gametes are sex cells)

What’s a gamete? Scientific name for a sex cell 2 Types of Sex Cells: In females: Egg An egg is a cell containing half of a woman’s chromosomes In males: Sperm Sperm is a cell containing half of a man’s chromosomes egg sperm

Where are gametes made? In Females: In Males: Ovaries Testes

Meiosis in females…. meiosis results in the production of one egg cell Babies are born with all the cells that will become eggs (approximately 150,000) After puberty, one egg will be made every month until eggs run out (approximately 400 eggs will be released)

Menopause When a woman no longer matures and releases eggs

Meiosis in males…. In males, meiosis results in the production of 4 new cells Babies are born with cells that will become sperm After puberty, sperm are made every day (approximately 300,000,000 per/day) until death