BIOLOGY 111 1st Edition Lecture 14 Outline of Last Lecture I. Light Energy ReactionsII. Calvin CycleIII. PhotorespirationIV. C4 PlantsV. CAM plants Outline of Current LectureI. Cell Division (prokaryotes vs. eukaryotes)II. DNA and ChromosomesIII. Cell CycleIV. RegulationsV. CheckpointsVI. Cancer CellsCurrent LectureCell Division- prokaryotes 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 moveThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.o the cell membrane turns inward to divide the cell (by tubulin-like proteins)- eukaryotes o more complex because there is more DNA which complicates replication and division o eukaryotes have linear DNAChromosomes are made of DNA DNA - contains four nitrogenous bases (deoxyribose sugar and phosphate)- they read from the 5' end to the 3' end o 5' end: phosphate group attachedo 3' end: hydroxyl group attached o connected by phosphodiester bond - hydrogen holds the base pairs together (i.e. A-T, G-C)o A and T bonded by 2 Hydrogen bondso G and C bonded by 3 Hydrogen bondsChromosomes- duplicating a single chromosome create a sister chromatids - sister chromatids are cohesive and are attached by a centromere o centromere is the point of attachmento cohesins bring them together o separases pull them apart - humans have 23 pairs or 46 total o autosomes (non-sex chromosomes) - 22 pairso sex chromosomes - 1 pair (XX or XY)a. X comes from either mother or fatherb. Y comes ONLY from father (father determines offspring sex)- Ploidy (number of sets of chromosomes that we have)o Diploid (2n) - humans have 23 pairs of chromosomes (most common ploidy)o Haploid (n) - gametes (sex determining cells) have 1 member of each pair of chromosomes (or 23 chromosomes)o Polyploids - more than two sets (i.e. most plants)Cell Cycle• divided into Interphase and Mitosis (division)• 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 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 plateo elongatesHow do chromosomes move along microtubles of the spindle? (know the process very well)• motor proteins walk chromosomes toward the spindle poles from the kinetochore • as you move the chromosome down the microtubule it shortens (the kinetochore end disintegrates)Regulation of Cell Phases • cytoplasmic regulations - causing the cell to transition from one phase to the next phase ◦ they synchronize cells to be in the same phase Checkpoints• there are 3 major checkpointso G1 (most important checkpoint) makes sure the cell is truly ready before it enters S phase  if its ready it continues on if it is not ready it enters the G0 phase (most cells are in this state)- this is like a waiting phase, the cells wait until they are ready- once they are ready they then can reenter the cycle at S phaseo G2o M• checkpoint proteinso acts as sensors to determine if the cell is in proper condition to divideo a cell cycle will be delayed until problems are fixed o loss of checkpoints lead to mutation and cancer o Cyclins and Protein Kinases are responsible for advancing a cell through the phases of the cell cycle  these activate or inactivate proteins by phosphorylation protein kinases control cell cycle must bind to a cyclin to be active (cyclin-dependent kinases) amount of cyclins varies through cycle - Cdk activity fluctuates - MPF activity is dependent of Cyclin concentration- high CDK activity - cell divides, low CDK activity - cell doesn't divide Active kinase ( CDK + Cyclin ) = MPF- kinase activates when CDK is bound with Cyclin Inactive Kinase ( CDK )- The Cyclin in the MPF gets degraded and breaks off, leaving CDK behind, deactivating kinase• G0 "resting state"o most cells need an external signal (i.e. chemical or physical signal) to exit the G0 phase and enter the S phaseo chemical signals o physical signals - normal cells are socially well-adjusted and respond to appropriate signals to divide or stop dividing (cancer cells ignore many importantsocial clues, benign - malignant)  anchorage dependence density-dependent inhibition Cancer Cells• it usually takes more than one single mutation (multiple hits model) to cause cancer◦ these acquired mutations must occur in several genes that regulate the cell cycle or repair DNA • Metastatic tumor (metastasis - moving of cancer cells to another area)◦ i.e. cancer cells begin in the breast but spread to lymph nodes and so on...• Once cancerous, cells continue to ignore normal cell cycle• Mutations in two types of cell cycle genes cause most types of cancer◦ proto-oncongenes◦ tumor suppressor