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Chapter 12&13

COMPLETE Honors General Biology CHAPTER 12 & 13 Notes -- 4.0ed this course

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BSC 2010C
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BSC 2010C­­0001  Ch. 12 and 13: Cellular Basis of Reproduction and Inheritance  Binary Fission  Bacterial chromosomes  Genes carried on single circular DNAmolecule • Up to 500x cell length  Minimal packaging  Complexed with few proteins and attached to plasma membrane at one point  Prior to cell division, genome copied  Copies attached to adjacent parts of membrane  Cell elongation and new plasma membrane separates two genomes  Plasma membrane pinches through cell  Eukaryotes have large, complex, multiple chromosomes  Human cells contain about 30,000-35,000 genes  Organized into separate, linear chromosomes  DNAcomplexed with proteins  Just prior to division, chromosomes become visible  Remain visible during division process  Somatic cells are body cells (not sex cells)  Ex. Hair cells  These cells need to contain the full set of chromosomes so that all the directions for functions and activities of the cell can be carried out.  Normally you inherit 23 chromosomes from each of your parents  This complete set of chromosomes (46) is known as the Diploid Number in Humans  Sex cells are known as gametes  These cells have half of the number of chromosomes that a body cell would have.  In humans this number is 23  Sooooo...Somatic (body) cells contain the diploid number of chromosomes compared to sex cells (haploid number)  Human cells:  Somatic cells-46 chromosomes (2n=46)  Sex cells-23 chromosomes (n=23)  What is a chromosome?  Prior to cell division, chromosomes are duplicated  Visible chromosomes consist of two identical sister chromatids attached at centromere  Sister chromatids can be separated…  Once sister chromatids separate they are again called un-replicated chromosomes  I know you are all thinking: WHAT?????  Summary  Humans have 23 pairs of chromosomes 1 [Type text] [Type text] [Type text]  They get numbers 1-23 from Mom and 1-23 from Dad = 46 (in males, 23 is non-d homologous)  These 46 chromosomes are found in somatic cells  Sex cells (gametes) have only 23  Each species has a specific diploid number  Cell Cycle  The cell cycle is like an “ alarm clock” that tells the cell when it is time to do some essential activities and when to divide.  It is regulated by many chemicals inside the cell.  Cell cycle divided into several steps (phases)  Interphase represents 90% or more of cycle time  G -Cell increases in size and increases supply of proteins and organelles 1  S-DNAsynthesis occurs (Copy DNA)  G -2ell prepares for division, increases supply of proteins necessary for division, checks for DNA damage  G –0cell stops progressing through cycle- will not divide  G Th0 =is a very important phase of cellular activity  The cell has the opportunity to stop progressing towards division, or DNAsynthesis  Why would this be important for a cell??????  Cells can phase into and out of G f0om several other cell cycle phases, its like an escape hatch  Different cells are in various phases of cycle even in same tissue  Also Different Tissues May Regulate Cycle Differently  Ex. Hair Divides Constantly  Nerve Tissue Never Divides InAdults  Adult Liver Tissue Does Not Divide, Except For Repair  How does a cell progress through the cell cycle?  Many biochemicals stimulate the transition  One of them is a Kinase  AKinase is an enzyme that catalyzes the transfer of a phosphate group fromATP to another molecule.  A Cdk is a cyclin dependent kinase  MPF (maturation promoting factor) is a co- chemical that is attached to Cdk  These chemicals stimulate the transition to cell division. When they are HIGH, the cell will DIVIDE.  Why do we care about this?  BECAUSE CYCLINAND CDK LEVELS AREALTERED IN CANCER CELLS…  Mitot
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