Mitosis and Meiosis Asexual v. Sexual Reproduction Cell dIVISION Mitosis and Meiosis Asexual v. Sexual Reproduction
Cell Division “process where 1 cell splits into 2” Replaces somatic (body) cells in multicellular organisms Allows for multicelullar growth Allows for asexual reproduction in plants
Chromosome – rod shaped structure made up DNA and protein a. held together by centromere - holds chromatids together until they separate during division b. only found during cell division
Chromosome Number Human/animal chromosomes – sex chromosomes and autosomes Humans have 46 chromosomes in somatic cells Karyotype – used to examine an individual’s chromosomes
Haploid Diploid Reproductive cells (sperm and egg) Somatic cells (body-all other cells) ½ the # of chromosomes (23) Has ALL chromosomes (46) half the DNA Has ALL DNA N = haploid 2N = diploid
Haploid/Diploid Problems Haploid Diploid = sex cell body cell ( x by 2) Diploid Haploid = body cell sex cell ( ÷ by 2) Diploid Diploid = body cell body cell Haploid Haploid = sex cell sex cell
Practice Problems Dogs have 42 chromosomes in their diploid cells. How many are in their haploid cells? If there are 23 chromosomes in a sperm cell, how many would be in the skin cell? If there are 46 chromosomes in a nerve cell, how many would be in a blood cell? If there are 23 chromosomes in a sperm cell, how many would be in a human ovum (egg)
Cell Division in Prokaryotes Binary Fision – two identical cells are produced from one cell * division in bacteria
Cell Division in Eukaryotes Mitosis Meiosis Asexual Reproduction Sexual Reproduction Division of diploid cells (somatic cells) Division of haploid cells (reproductive cells) Results in 2 identical daughter cells Results in 4 haploid daughter cells 1 division 2 divisions
Cell Cycle “series of events leading to cell division” Interphase – occurs before mitosis begins - longest part of the cell cycle
Mitosis Asexual Reproduction Diploid cells split into 2 identical diploid cells Allows body cells to be replaced and cells to GROW
Phases of Mitosis 1. Prophase Chromatin coils to make chromosomes 2 pairs of centrioles move apart and spindle fibers appear 2 types of spindle fibers a. kinetochore fibers b. polar fibers
2. Metaphase Kinetochore fibers move chromosomes to the center (equator) of the cell
3. Anaphase Spindle fibers grab the centromeres of each chromosome and pull the chromatids apart Chromatids now separate (now called daughter chromosomes) and are pulled to the opposite poles
4. Telophase Spindle fibers disassemble and chromosomes return to a less tightly coiled chromatin state Nuclear envelope and membrane reappear Cytokinesis – splitting of the cytoplasm a. cleavage furrow b. 2 cells are equal in size c. each cell receives an identical copy of the original cell’s chromosomes
Cytokinesis “division of the cytoplasm” *animal cell – creates 2 new cells * Plant cell – forms cell plate
Meiosis “sexual reproduction” Fusing of 2 haploid gametes to form 1 diploid zygote
Stages 2 divisions a. Meiosis I
b. Meiosis II
Sources of Genetic Variation Crossing – over Fertilization Independent Assortment