Transcript meiosis
• MITOSIS: cell division that produces 2 daughter cells identical to the parent cell • MEIOSIS: cell division that produces 4 daughter cells with half the number of chromosomes as the parent cell = sex cells Cellular Reproduction • Interphase • Most of cell life spent here • CHROMOSOMES replicate and attach at CENTROMERE • Nuclear membrane still present • Centrioles Replicate Prophase Chromosomes condense Nuclear membrane disappears Spindle fibers form between centrioles Metaphase Chromosomes line up in the Middle (equator) of the cell They are connected to the spindle fibers Anaphase chromosome splits at each centromere Chromosomes move to opposite poles of the cell Telophase Return to interphase conditions Nuclear membrane forms CYTOKENESIS = division of remaining cell parts 2 identical daughter cells are formed • Chromosomes replicate (copy) during this phase… A. B. C. D. E. ANAPHASE INTERPHASE METAPHASE PROPHASE TELOPHASE • The nuclear membrane disappears in this phase… A. B. C. D. E. ANAPHASE INTERPHASE METAPHASE PROPHASE TELOPHASE • During this stage the nuclear membrane is formed around the chromosomes… A. B. C. D. E. ANAPHASE INTERPHASE METAPHASE PROPHASE TELOPHASE • Chromosomes line up in the middle of the cell and connect to the spindle fibers… A. B. C. D. E. ANAPHASE INTERPHASE METAPHASE PROPHASE TELOPHASE • Most cell life is spent in this stage… A. B. C. D. E. ANAPHASE INTERPHASE METAPHASE PROPHASE TELOPHASE • During this stage the chromosome split at each centromere… A. B. C. D. E. ANAPHASE INTERPHASE METAPHASE PROPHASE TELOPHASE • Chromosomes condense and appear in this phase… A. B. C. D. E. ANAPHASE INTERPHASE METAPHASE PROPHASE TELOPHASE • During this stage the chromosomes move to opposite poles… A. B. C. D. E. ANAPHASE INTERPHASE METAPHASE PROPHASE TELOPHASE • During this stage 2 identical daughter cells are formed… A. B. C. D. E. ANAPHASE INTERPHASE METAPHASE PROPHASE TELOPHASE How Mitosis leads to growth and repair Your growth Root and shoot growth at tips in plants Replacement of skin and stomach cells Blood cell replacement Repairing injury to your skin Plant repair • Reproduction by one parent cell • Identical offspring • Read pages 56-57 to find examples of organisms that reproduce this way • Yeast • Bacteria • Hydra • Potatoes • Sea Star • Sexual Reproduction = reproduction by two parents • Results in SEX CELLS = egg or sperm • Sex cells have ½ the number of chromosomes as the parent cell • Why is that important? • • • • Meiosis-1 twin chromosomes separate = 2 cells Meiosis-2 chromosomes split apart = 4 cells Human cell has 46 chromosomes Human sex cell has ?? • 23 • Fertilization = joining of sperm and egg • Equals a ZYGOTE • Look at picture on 66 • Grows by MITOSIS • Offspring not identical to parent Asexual= an exact copy of the cell • Sexual = a cell with ½ of the original chromosome number • In which of the following is the offspring an exact copy of the parent cell… A. Meiosis B. Mitosis • In which of the following is the offspring a sex cell with ½ the number of chromosome… A. B. Meiosis Mitosis Mitosis •Offspring cell has chromosomes identical to parent •Begin with parent cell Meiosis •Chromosomes copied •Chromosomes separate •Cell divides in two •Cell divides in two again •Offspring cells have half the chromosomes of parent • In a few paragraphs, explain to me the process of meiosis. Their discovery has allowed us to understand how the structure of DNA makes it able to copy itself How TRAITS are passed from parent to offspring Twisted ladder Rungs = Molecule Bases A,T,C,G Sides = Sugar and Phosphate DNA found on chromosomes Contains info. About organisms traits Chromosomes are long strands of DNA Genes are sections of DNA on a chromosome that controls a trait Direct the building of proteins that make up your cells Unzips like a zipper into 2 halves Free floating bases in the nucleus attach to the unzipped DNA to make a new ladder GOAL = locate all genes on the 46 human chromosomes Map the sequence of all base pairs GENOME = complete set of genetic instructions for an organism At least 100,000 genes organized to 46 chromosomes (3 billion+ base pairs) WHY? Detect and treat genetic disorders Cystic fibrosis MD Cancers Identity of a person DNA from blood, hair, skin GENETIC FINGERPRINT Mom’s Chromosomes(23) +Dad’s Chromosomes(23) Genes on chromosomes for different traits Like chromosome pairs line up = Zygote with 46 chromosomes acting together to produce traits • Dominant gene that will show up if present • Recessive gene is “weaker” • Will only show if person has two copies of this gene •Pass the Genes, Please • A change that occurs when DNA copies itself • A mistake in the copying process • In a sex cell this is passed on to offspring