The extended active form of DNA is found in Euchromatin DNA unravels from The Cell Cycle histone proteins Activities of DNA o DNA replication Occurs in the S phase o Transcription Interphase Occurs before cell division Divided into 3 phases o G1 phase Occurs when DNA is transcribed into a pre mRNA The cell is growing refereed to as hypertrophy It s the longest phase in interphase hours weeks months or years Hours to weeks epitherial cells Years hepatocytes When cells stop dividing they are in the G0 phase o S phase Synthesis phase Proteins synthesis occurs but the major event in the S phase is DNA synthesis refereed to as DNA replication DNA replication is refereed to as semi conservative replication because the 2 molecules of DNA will each contain an old polynucleotide chain which acted as a template and the newly synthesized polynucleotide strand If DNA replication in the S phase is aborted mitosis can t occur o G2 phase Cell produces mostly globular proteins such as enzymes required for the initiation and maintenance of cell division Such proteins are referred to as the G0 proteins o Nuclear division that parcels out the duplicated replicated DNA o Required for cell division for mitosis MPF mainstream promotional factor cyclins cyclin dependent kinase o 4 phases in sequence Prophase Nuclear membrane disintegrates Nucleoli disappear Spindle fibers sprout from centrioles Chromosomes highly condense form of heterochromatin Metaphase Anaphase Cell Division Mitosis Telophase Nuclear membrane forms Nucleoli forms Spindle fibers disintegrate and disappear Euchromatin and the newly formed daughter cells begin interphase where you will have protein synthesis o Growth by increase in cell number interphase was growth by cell size Cytokinesis o Transcription 2nd activity of DNA in the cell is transcription part of proteins synthesis Occur in the nucleus DNA polynucleotide strands One strand will act as a template for the synthesis of the pre mRNA based on the law of complementary based pairing if you have T A C G C A the pre mRNA is A U G C G U the 3 base sequence in mRNA is called a Codon The 3 base sequence in DNA is called a Triplet The other strand is called the coding stand not used as a template After transcription the pre mRNA primary transcript is composed of introns and exons The introns do not code for amino acids Exons code for specific amino acids Hence the pre mRNA is edited to remove the introns leaving only the exons this will be the mRNA mRNA all exons The mRNA translocates through the nuclear pore into the cytoplasm where translation occurs o Translation Occur in the cytoplasm Involves all 3 types of RNA rRNA forms part of the ribosome mRNA brings codons tRNA transfer RNA This is cloverleaf shaped with amino acids attached to the tail of the tRNA and 3 base sequence called the anticodon attached to the heard of the tRNA When the ribosome covers a codon on the mRNA tRNA with complementary bases anticodon will attach to the codon bringing along an amino acid Triplet GGG mRNA CCC Anticodon on tRNA GGG The anticodons are the same as the triplets except if the triplets contain a T its replaced by U Tissue The Living Fabric Tissues Tissue Level 4 Primary Tissues Epithelial A tissue is composed of similar cells put together to perform specific functions Most cells in the human body aggregate to form tissue Most cells are not independent they connect with other cells o Polarity o Avascular but has a high regenerative capacity only if the epithelial tissues are supported by vascularized connective tissue o All epithelial tissues supported by basement membrane which acts as a selective membrane to regulate substances that diffuse from the underlying connective tissue to the overlying epithelial tissue o 2 classes of epithelial tissue Membranous Sheet like Glandular Aggregate of secretory cells Connective Muscle Nervous Membranous Epithelial Tissue Simple epithelia o A single of epithelial cell o Simple Squamous Epithelial Tissue A single layer of flat cells with flattened nuclei placed underneath the apical surface of the cells Location Forms part of the filtration membrane in the nephrons in the kidneys Part of the respiratory membrane in the lungs Lines structures in the circulatory system This system is made up of the cardiovascular blood circulates and the lymphatic system lymph circulates Lines structures in the circulatory system is referred to as endothelium Forms part of the serous membrane referred to as the mesothelium o Simple Corboidal Epithelial Tissue A single layer of cube like cells with centrally placed spherical nuclei Location Lines the tubular of the nephrous in the kidneys Outer layer surrounding each ovary referred to as the Germinal Epithelial A single layer of cells with elongated nucei placed closer to the surface of celss Nonciliated Ciliated Will come with goblet cells to secrete a muco polysaccharide called mucin Mucin water mucus o Ciliated Simple Columnar Epithelial Tissue Location Parts of the respiratory system goblet cells secrete mucus which is moved by unidirectional current produced by the cilia Fallopian tubes cilia beat to create unidirectional current that moves ovum or conceptus from the Fallopian tube o Nonciliated Simple Columnar Epithiila Tissue Location Lines the stomach small intestine large intestine rectum and anal canal Lining of the small intestine express microvilli o Are named for the epithelial cell type on the apical surface of the stratified Stratified epithelial Simple columnar cells have cilia bronchi tube like structures leading into the lung fallopian tubes o the simple columnar epithelial cells in the bronchi have goblet cells produce mucin which interacts with water to form mucus hence cilia beat to create an unidirectional current that moves mucus laden with debris and pathogens moves this away from the lungs lining of the fallopian tubes and the superior portion of the uterus cilia beat to create a unidirectional current that propels ovum egg or the conceptors fertilized egg into the uterine cavity non ciliated digestive tract from the stomach to small intestine to large intestine to rectum to anal canal o small intestine non ciliated simple columnar epithelial lining of the small intestine expresses microvilli which increase surface area available for absorption in the small intestine Psedudostratified columnar epithelium A single layer of tall cells of different heights hence the nuclei appear at different heights
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