BCOR 103 1st Edition Lecture 20Outline of Last Lecture I. CDK Regulation: Phosphorylation/DephosphorylationII. Transition Points in Cell CycleIII. Rb Phosphorylation Defines Restriction PointIV. CDK Activation and Inhibition Regulates G1-S TransitionOutline of Current Lecture I. Regulation of TransitionsII. MeiosisIII. Stem CellsCurrent Lecture- Regulation of the G2-M Transitiono Cells monitor replicated DNA and cell size before committing to M phase.o M-phase CDKs phosphorylate multiple substrates to prepare for chromosome separation, nuclear division, and cytokinesis.o CDKs, Aurora kinases, and Polo-like kinases function in positive feedback loop to regulate entry into M phase.- Early Events in G2-M Transitiono Nuclear envelope breakdown requires phosphorylation of nuclear lamina- Sister Chromatid Cohesion and Condensationo Cohesin proteins: connect sister chromatids togethero Condensin proteins: condense sister chromatids for faithful segregation of chromosomes in mitosis. - Loss of M-phase CDK triggers Phosphataseso Inactivation of M-phase CDKs triggers phosphatases to stimulate myosin-dependent contractile ring closure. - Meiotic RecombinationThese 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 Meiotic recombination allows for exchange of genetic information (DNA) between homologous chromosomes.o Synaptonemal complex: protein complex that keeps homologous chromosomes closely aligned through pachytene stage.- Mos Kinase: a Component of the CSFo CSF (Cytostatic Factor).o Mos Kinase inhibits a kinase cascade that inhibits the APC.- Differentiation of Human Cells and Tissueso Rapid proliferation of embryonic cells differentiationtissues; organso ~100 trillion cells in adult human body. Classified into 20 different categories based on structure and function.- Cell Types are determined during Embryonic Developmento Cellular differentiation must occur at right time and place within embryo.o Must have coordination between cell cycle regulation, mRNA transcription, and protein synthesis. o Once differentiated, most cells will maintain a G0 arrest regardless of their location or environment.o Radical de-differentiation is very unusual, but modulations of a differentiated state can occur depending in environmental cues. Usually requires alternate protein synthesis. - Cells in Different Tissues have Different Fateso Some cells never reproduce and cannot be replaced if they are lost. E.g. nerve cells, heart muscle cells, eye lens cellso Most cells are continually dying and must be replaced. Some cells are replaced by duplication of already differentiated G0 cells.- E.g. epithelial cells of liver; endothelial cells of blood vessels; skin fibroblasts (wound repair). Some cells are replaced by differentiation of stem cells.- E.g. gut epithelial cells, blood cells.- Properties of Stem Cellso Defining properties of stem cells: 1. It is not terminally differentiated. 2. Proliferation: It can divide without limit for lifetime of host. 3. Each daughter cell has a choice:- A. remain a stem cell (self-renewal).- B. undergoes irreversible terminal differentiation. - Pluripotent Stem Cellso Pluripotent stem cells: Can differentiate into wide variety of cells. Embryonic stem cells have the broadest differentiative capacity.- Embryonic Stem Cells in Therapeutic Cloningo Nucleus from patients’ somatic cell is transferred to enucleated egg.o Embryonic stem cells from this early embryo can be differentiated into desired cell type and put back into patiento This type of transplant avoids complications associated with immune system