BIOM 121 1nd EditionExam # 3 Study Guide Lectures: 14-19Lecture 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 eukaryoteso prokaryotes have circular DNAo 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 moveo 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 - growtho 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 aparto Prometaphase  kinetochore (microtubule protein attachment) o Metaphase  Mitotic spindle formed and functional  centrosomes are at the poles  chromosomes line upo 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 plateo elongates- Internal factors that regulate the cell cycleo 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 coordinateskey 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 checkpointo 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 CdkLecture 15 (March 20)- Genetics is the scientific study of heredity and hereditary variationo 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 gameteso 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 cycleso The process of meiosis and fertilization maintain a species’ chromosome count during the sexual life cycleo 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 bymitosis - Mitosis vs Meiosiso 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 Cellso A