BIOM 121 1nd Edition Exam 3 Study Guide Lectures 14 19 Lecture 14 March 18 Cell Cycle an organized sequence of events in the life of a cell from its origin until it divides into daughter cells Cell Division for both prokaryotes and eukaryotes includes mostly the passing of identical genetic material DNA to the two new daughter cells Prokaryotic Cell Division o very simple division not as complicated as eukaryotes o prokaryotes have circular DNA o the cell basically divides in two binary fission o initially they must duplicate everything so that both cells after division have the same thing the origin of replication where division begins actin like proteins help chromosomes move o the cell membrane turns inward to divide the cell by tubulin like proteins Eukaryotic Cell Division o more complex because there is more DNA which complicates replication and division o eukaryotes have linear DNA Interphase o G1 growth o S DNA synthesis DNA is duplicated o G2 grows more making proteins and organelles that are necessary uncondensing chromosomes centrosomes microtubules come from here Mitosis and Cytokinesis division o a cell divides to produce 2 new cells genetically identical to the original o Prophase nuclear envelope starts disintegrating chromosomes are condense mitotic spindle begins formation centrosomes move apart o Prometaphase kinetochore microtubule protein attachment o Metaphase Mitotic spindle formed and functional centrosomes are at the poles chromosomes line up o Anaphase mitotic spindles pull chromatids apart chromosomes move to opposite ends elongating the cell o Telophase and Cytokinesis nuclear envelope and nucleoli reappear chromosomes are less condense two genetically identical nuclei are formed at the end of mitosis Cytokinesis division of cytoplasmic material a contractile ring of actin microfilaments forming a cleavage furrow in an animal cell animal cells cleave from outside in plants start from inside out o Vesicles derived from Golgi Apparatus move to the center coalesce and form cell plate o elongates Internal factors that regulate the cell cycle o The frequency of cell division varies with the type of cell o The cell cycle is driven by specific signaling molecules present in the cytoplasm i e If there are two cells at different phases of the cell cycle one being in the S phase and the other being in G1 phase the nucleus of the cell in G1 would immediately enter the S phase because it was stimulated by signaling molecules present in the cytoplasm from the first cell already in S phase o Also sequential events are directed by a distinct cell cycle control system a cyclically operating set of molecules in the cell that both triggers and coordinates key events in the cell cycle that is regulated at certain checkpoints o Both internal and external signals control the cycle checkpoints via signal transduction pathways Checkpoint in the cell cycle is a control point where stop and go signals are used to regulate the cycle There are three major checkpoints G1 G2 and M phases G1 checkpoint is the restriction point that seems to be the most important If a cell receives a go signal at the G1 checkpoint it will usually complete the G1 S G2 and M phases If a cell is stopped doesn t receive the go signal it will exit the cycle switching to a nondividing state called the G0 phase most cells in the human body are in this phase When the cell is ready to be used it will be called back from the G0 phase and reenter the cell cycle G2 checkpoint is MPF explained below M phase checkpoint is the final checkpoint and it is responsible for making sure each daughter cell does not end up missing or receiving any extra chromosomes Cyclin dependent kinases Cdks o Protein kinases are enzymes that activate or inactive other proteins by phosphorylation and to be activated the kinase must be attached to a cyclin a protein with cyclically fluctuating concentration in the cell o The activity of a Cdk rises and falls with changes in the concentration of the attached cyclin MPF maturation promoting factor or M phase promoting factor o A cyclin combined with a Cdk make an MPF a G2 checkpoint o Triggers the cells passage past the G2 checkpoint into M phase o MPF acts directly as a kinase and indirectly by activating other kinases causing phosphorylation to promote mitosis o In anaphase the end of mitosis MPF switches itself off by destroying its own cyclin and recycling Cdk Lecture 15 March 20 Genetics is the scientific study of heredity and hereditary variation o Heredity or Inheritance is the transmission of traits from one generation to the next o There is hereditary similarities why we look like our relatives and variation why we look different to every other individual including our relatives Asexual Reproduction a single individual is the sole parent and passes copies of all its genes to its offspring without the fusion of gametes o i e a single celled eukaryote can reproduce asexually by mitotic cell division Sexual Reproduction two parents give rise to offspring that have unique combinations of genes inherited from the two parents The offspring vary genetically from their siblings and both parents variations on a common theme of family resemblance exhibiting genetic variation Sexual life cycles o The process of meiosis and fertilization maintain a species chromosome count during the sexual life cycle o Sexual life cycles differ in the timing of meiosis relative to fertilization and in the points of the cycle at which a multicellular organism is produced by mitosis Fertilization fusion of a sperm and an egg creating a diploid zygote that will develop by mitosis Mitosis vs Meiosis o Mitosis DNA is copied and allocated equally to two daughter cells The genomes of the offspring are virtually exact copies of the parent s genome o Meiosis gamete formation involves a type of cell division reducing the number of sets of chromosomes to half of the original i e from diploid to haploid Meiosis is distinguished from mitosis by three events Prophase 1 Metaphase 1 and Anaphase 1 explained below either haploid or diploid cells can undergo mitosis but only diploid cells can undergo meiosis Sets of Chromosomes in Human Cells o A Karyotype is an ordered display of chromosomes that are arranged in pairs and in the order by length beginning with the longest pair o Homologous chromosomes homologs two chromosomes that are the same in length centromere position and staining pattern Both chromosomes of each pair