Presentation on theme: "Sexual Reproduction and Meiosis"— Presentation transcript:
1Sexual Reproduction and Meiosis Sexual Reproduction --two parents combine
2Gametes: Sex Cells 1. The sex cell from the male parent is sperm. a. Sperm head is almost all nucleus (genetic info)2. The sex cell from the female parent is the egga. Eggs are large and contain food material.Gametes: Sex Cells
3Diploid / Haploid Cells that have 2 sets of DNA are diploid. • Diploid is 2n.• All of your body cells are 2nA sex cell with one set of DNA is haploid.• Haploid is n• sperm & egg (gametes) are haploid
4Fertilization-- joining of egg and sperm n + n = 2n or = 46 chromosomes(23 chromosomes from your dad join with 23 chromosomes from your mom (n=23).)fertilization forms a zygote- grows to become an embryo by mitosis
5The zygote has the diploid (2n = 46) chromosome number for that organism. The zygote (or 1st body cell) does mitosis to grow and develop.
6Stages of Meiosis Prophase I - 1. double stranded chromosome and spindle fibers appear.2. The nuclear membrane and nucleolus disappear.3. Tetrads form (4 chromatids).4. Crossing over occurs.
7Metaphase I - The pairs of chromosomes (tetrads) line up in the center of the cell. Anaphase I - double stranded chromosomes (tetrad) separate from its twin. Each one is pulled to opposite ends of the cell.
8NOT FOLLOWED BY INTERPHASE! Telophase I - The cytoplasm divides and two cells form. Each chromosome is still double stranded.NOT FOLLOWED BY INTERPHASE!
9Prophase II - the double stranded chromosomes and spindle fibers reappear in each new cell.
10Metaphase II - the double stranded chromosomes move to the center of the cell: Anaphase II - The centromere divides and the chromatids separate and move to opposite ends of the cell.
11Telophase II - the spindle fibers disappear and a nuclear membrane forms around the chromosomes at each end of the cell.- followed by cytokinesis II
15III. The Importance of Sex Chromosomes A. Body cells have chromosomes that are found in pairsB. The 46 human chromosomes form 23 pairs of chromosomesC. The pairs form because the chromosomes are alikeThe 23rd pairdetermines the sex orgender of the child.XX= femaleXY= male