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Genetics is a study of heredity How traits are passed from one generation to the next. DNA is the material that holds the information about your traits • Chromosomes are long pieces of DNA. • Segments of DNA along the chromosomes hold instructions for different traits How are traits passed to offspring? Two types of reproduction: Asexual and Sexual Asexual reproduction • Prokaryotes • Requires only ONE parent • Offspring inherit DNA from just one parent and are therefore identical to parent. • Process is called BINARY FISSION and happens just like mitosis to form TWO identical offspring. Sexual Reproduction • Eukaryotes: plants, animals, fungi and protists • TWO parents • Offspring get a complete set of chromosomes from BOTH parents for a total of TWO copies of every gene in all body cells. • Requires specialized SEX CELLS called gametes (egg and sperm cells) Sexual Reproduction • Offspring have some traits like the mother and some like the father. • How are SEX CELLS made??? Meiosis makes sex cells • • • • Makes egg and sperm cells Like mitosis DNA gets copied before it starts Different because the nucleus divides TWO TIMES to make four cells • Each sex cell has just ONE copy each chromosome, where body cells have TWO copies REMEMBER: • Gametes (egg and sperm cells) have HALF as much DNA (one set) as body cells (two sets). Fertilization: no peeking… You are kidding, right??? This works PERFECTLY • Egg and sperm each give ONE copy of DNA to the baby so that it has TWO copies, one from each parent. • This is how you get traits from both your mom and your dad Humans • We inherit one set of 23 chromosomes from each parent for a total of 46 chromosomes. • Scientists number them from 1-23 • Each matching pair of chromosomes (ex: chromosomes #1 inherited from mom and #1 inherited from dad are called HOMOLOGOUS CHROMOSOMES. Mitosis To make BODY cells Purpose Meiosis To make SEX cells for reproduction To grow To repair injuries Sex cells = gametes = eggs and sperm cells Mitosis Which cells do it Happens in all BODY cells Meiosis Happens in SEX organs of eukaryotes Mitosis # Daughter Cells TWO daughter cells Meiosis FOUR daughter cells Mitosis How much DNA In Eukaryotes, SAME amount of DNA as parent cell. Daughter cells identical to parent cell Meiosis In Eukaryotes, HALF as much DNA as parent cell. Daughter cells are ready to combine with another sex cell to reproduce. Mitosis In Humans: TWO sets of 23 chromosome: One set inherited from mom and one set inherited from dad Meiosis ONE set of 23 chromosomes: MIXED from parent’s DNA Mitosis Remember Meiosis My-TOE- sis Mini-Meiosis Mitosis makes body cells for growth and repair Meiosis makes SEX cells to make a mini me.