BIOLOGY 111 1st Edition Lecture 14 Outline of Last Lecture I Light Energy Reactions II Calvin Cycle III Photorespiration IV C4 Plants V CAM plants Outline of Current Lecture I Cell Division prokaryotes vs eukaryotes II DNA and Chromosomes III Cell Cycle IV Regulations V Checkpoints VI Cancer Cells Current Lecture Cell Division prokaryotes 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 These 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 DNA Chromosomes 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 attached o 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 bonds o G and C bonded by 3 Hydrogen bonds Chromosomes duplicating a single chromosome create a sister chromatids sister chromatids are cohesive and are attached by a centromere o centromere is the point of attachment o cohesins bring them together o separases pull them apart humans have 23 pairs or 46 total o autosomes non sex chromosomes 22 pairs o sex chromosomes 1 pair XX or XY a X comes from either mother or father b 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 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 How 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 checkpoints o 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 phase o G2 o M checkpoint proteins o acts as sensors to determine if the cell is in proper condition to divide o 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 cyclindependent 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 phase o 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 important social 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 genes