Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Cell Rep. 1 Cell Reproduction I. Chromosomes (Eukaryotic Cells) *Recall…DNA molecules are long, thin, and made of six billion pairs of nucleotides (DNA double helix)(twisted stair case) A. CHROMOSOME STRUCTURE 1) Chromosomes coiled DNA with proteins and rod shaped 2) Histones the proteins that DNA wraps around 3) 2 identical Chromatids make up a Chromosome 4) Chromatids held together by a Centromere 5) Centromere the constricted area of the chromosome B. CHROMOSOME NUMBERS * Each species has a specific # of chromosomes 1) Sex Chromosomes and Autosomes a) Sex Chromosomesdetermine sex of organism 1) XYmale…XXfemale b) Autosomesall the other chromosomes c) Humans 46 chromosomes (23 from each parent)2 of 46 Sex Chr.44 are autosomes d) Homologous Chromosomes chromosomes (2) that are same shape, size, and have the same genes (autosomes) II. Cell Division *Cells come from cellscell division is the process of cell reproduction. A. CELL DIVISION IN PROKARYOTES 1) Binary fission division of prokaryotic cell into 2 Offspring B. CELL DIVISION IN EUKARYOTES *Mitosis result1 cell makes 2 genetically identical cells (unicellular and tissues in Multicell.) Cell Rep. 2 * Meiosisreduces chromosome # by ½. new cell joins with another organisms cell …ex.-->sperm(23) and egg (23) …which gives a new cell with (46) 1) The Cell Cycle a) a repeating set of events that make up the life of a cell b) Interphase the time between cell divisions DNA is copied 3) Mitosis a) division of nucleushappens during cell division b) continuous process c) 4 steps of mitosis (in the following order) 1)Prophase (2)Metaphase (3)Anaphase (4) Telophase d) Prophase copied DNA coils into chromosomes. e) Metaphase chromosomes line up along midline of dividing cell f) Anaphasechromatids move towards opposite ends (poles)(centrosomes) of cell. Cell Rep. 3 g) Telophase chromosomes reach poles and cytoplasm divides…then cell divides (Cytokinesis) III. MEIOSIS (gives haploid reproductive cells) *A process of nuclear division that reduces the number of chromosomes in new cells to half the number in the original cell. *Humansmeiosis…producesgametes(haploid)(23chr.) (egg)(sperm)zygote46chr. A. STAGES OF MEIOSIS (Meiosis I and Meiosis II) 1) Meiosis I a) Synapsis homologous chromosomes pair up one is paternal (your dads)one is maternal (your moms) b) Tetrad pair of homologous chromosomes c) Crossing over homologous chromosomes Cell Rep. 4 switch chromatid pieces (during synapsis) genetic material is exchanged between maternal and paternal chromosomes this produces new mix of genetic material (genetic recombination) d) End of Meiosis I2 cells w/half the number of chromosomes (23) 2) Meiosis II a) Each cell after MeiosisI goes through MeiosisII b) so2 cells give 4cells(sperm cells)or (egg cell) d) End of Meiosis II4 cells each w/ (23 chrom.) 4) Asexual and Sexual Reproduction a) Asexual Reproduction offspring produced from 1 parent (binary fission (unicellular))or (mitosis) Parents AND offspring genetically IDENTICAL b) Sexual Reproduction (meiosis)… (sperm + egg)=offspring Parents AND offspring genetically DIFFERENT