BIOL 1107 1nd Edition Exam 4 Study Guide Lectures 25 30 Each section below includes material from the lecture homework and textbook Chapter 12 The Cell Cycle 12 1 and 12 2 Unicellular organisms division of one cell reproduces entire organism Multicellular organism depend on cell division for development from fertilized cell growth and repair Cell division is an integral part of cell cycle life of a cell from formation to its own division Cell division Ability of organisms to produce more of their own kind best distinguishes living things from nonliving matter Continuity of life is based on reproduction of cells or cell division Most cell division results in daughter cells with identical genetic info DNA Exception is meiosis a special type of division that can produce sperm and egg cells Cellular Organization of Genetic Material All DNA in cell constitutes cell s genome a genome can consist of a single DNA molecule common in prokaryotic cells or a number of DNA molecules common in eukaryotic cells DNA molecules in a cell are packages into chromosomes Eukaryotic Cell Division In preparation for cell division DNA is replicated and chromosomes condense Each duplicated chromosome has two sister chromatids joined copies of the original chromosome which separate during cell division Centromere narrow waist of the duplicated chromosome where the two chromatids are most closely attached Eukaryotic chromosomes consist of chromatin a complex of DNA and protein that condenses during cell division Every eukaryotic species has a characteristic number of chromosomes in each cell nucleus Somatic cells nonreproductive cells have two sets of chromosomes Gametes reproductive cells sperm and eggs have half as many chromosomes as somatic cells During cell division two sister chromatids of each duplicated chromosomes separate and move into nuclei Once separate the chromatids are called chromosomes Cell Cycle It consists of mitotic phase M phase and interphase o Mitotic M phase mitosis and cytokinesis o Interphase cell growth and copying of chromosomes in preparation for cell division Eukaryotic cell division consists of o Mitosis division of genetic material in nucleus o Cytokinesis division of cytoplasm Gametes are produced by a variation of cell division called meiosis Meiosis yields nonidentical daughter cells that have only one set of chromosomes half as many as the parent cell Interphase 90 of cell cycle can be divided into subphases G1 phase first gap S phase synthesis G2 phase second gap Cell grows during all three phases but chromosomes are duplicated only during S phase Mitotic Phase 1882 German anatomist Walther Flemming developed dyes to observe chromosomes during mitosis and cytokinesis Five phases of mitosis prophase Prometaphase metaphase anaphase telophase Cytokinesis overlaps the latter stages of mitosis Mitotic spindle a structure made of microtubules that controls chromosome movement during mitosis In animal cells assembly of spindle microtubules begins in the centromere the microtubule organizing center The centrosome replicates during interphase forming two centrosomes that migrate to opposite ends of the cell during prophase and prometaphase Aster a radial array of short microtubules it extends from each centrosome The spindle includes centrosomes the spindle microtubules and the asters During prometaphase some spindle microtubules attach to kinetochores of chromosomes and begin to move the chromosomes Kinetochores protein complexes associated w centromeres At metaphase the chromosome are all lined up at the metaphase plate an imaginary structure at the midway point between the spindle s two poles In anaphase sister chromatids separate and move along the kinetochore microtubules toward opposite ends of the cell The microtubules shorten by depolymerizing at their kinetochore ends Nonkinetochore microtubules from opposite poles overlap and push against each other elongating the cell In telophase genetically identical daughter nuclei form at opposite ends of the cell Cytokinesis begins during anaphase or telophase and the spindle eventually disassembles In animal cells cytokinesis occurs by a process known as cleavage forming a cleavage furrow In plant cells a cell plate forms during cytokinesis Evolution of Mitosis Since prokaryotes evolved before eukaryotes mitosis probably evolved from binary fission Certain protists exhibit types of cell division that seem intermediate between binary fission and mitosis Prokaryotes bacteria and archaea reproduce by a type of cell division called binary fission In binary fission chromosome replicates beginning at origin of replication and the two daughter chromosomes actively move apart Plasma membrane pinches inward diving the cell into two Chapter 13 Meiosis and Sexual Life Cycles Living organisms are distinguished by their ability to reproduce their own kind Some Definitions Genetics scientific study of heredity and variation Heredity transmission of traits from one generation to the next Variation demonstrated by the differences in appearance that offspring show from parents and siblings Genes units of heredity made up of segments of DNA o They are passed to next generation via reproductive cells called gametes sperm and eggs o Each gene has a specific location called a locus on a certain chromosome o Most DNA is packaged into chromosomes Asexual v Sexual Reproduction Asexual reproduction a single individual passes genes to its offspring without the fusion of gametes Clone group of genetically identical individuals from the same parent Sexual reproduction two parents give rise to offspring that have unique combinations of genes inherited from the two parents Offspring acquire genes from parents by inheriting chromosomes In a literal sense children do not inherit particular physical traits from their parents It is genes that are actually inherited Life cycle generation to generation sequence of stages in the reproductive history of an organism Sex chromosomes determine the sex of the individual are called X and Y o Human females have a homologous pair of X chromosomes XX o Human males have one X and one Y chromosome Remaining 22 pairs of chromosomes are called autosomes Sets of Chromosomes in Human Cells human somatic cells any cell other than a gamete have 23 pairs of chromosomes 46 chromosomes karyotype an ordered display of the pairs of chromosomes from a cell two chromosomes in each pair are called homologous chromosomes or homologs