Biology Exam 2 1 Transcription 2 Translation 5 steps mRNA is made from a DNA template mRNA is processed before leaving the nucleus mRNA moves to the ribosomes to be read Every 3 bases on the mRNA is called a codon and codes for a particular amino acid in translation 1 The small ribosomal subunit attaches to mRNA and then the first tRNA binds to 2 The large ribosomal subunit attaches and allows the second tRNA to pair up with 3 Peptide bond forms linking the two amino acids together 4 The ribosome moves to the next codon and continues building the amino acid 5 Finally the ribosome reaches a stop codon causing the ribosome to release the first codon the second codon chain from the mRNA Processing of mRNA after transcription Modifications of mRNA One end of the RNA is capped Poly A tail is added Introns removed Exons kept What did we learn from the human genome project HGP The human genome consists of about 3 billion bases and 25 000 genes Human genome sequenced in 2003 There are many polymorphisms or small regions of DNA that vary among individuals Genome size is not correlated with the number of genes or complexity of the organisms Mutations Defined as a change in the DNA sequence Point mutations A single nucleotide has been replaced with another Frame shift mutations A nucleotide has been added or deleted Altering DNA to achieve a specific desired result 3 tech rDNA contains DNA from 2 or more different sources Biotechnology 1 Recombinant DNA requires a vector what is a vector what is a plasmid a means to transfer foreign genetic material into a cell accessory rings of DNA in bacteria replicates independently of bacterial DNA how do we transfer DNA use restriction enzymes cuts DNA at specific locations produced by bacteria restricts growth of viral DNA May leave sticky ends DNA ligase is also required Seals DNA fragments together Allows a portion of DNA to be incorporated into another sample of DNA as long as it was cut with the same restriction enzyme G0 break from cell division P53 detects damage Activates repair enzymes BRCA1 or Activates enzymes that initiate apoptosis What goes wrong in cancer cells Cancer is the result of uncontrolled cell division Characteristics 1 cancer cells are not regulated by contact inhibition 2 cancer cells no longer appear differentiated 3 proto oncogenes mutate Referred to as oncogenes Caused by gene mutations that no longer allow the cell to properly regulate the cell cycle A single cell must accumulate several mutations before cell division is uncontrollable Any gene that encodes a protein that promotes cell division at an inappropriate time May encode a faulty receptor May encode for a self stimulatory growth factor 4 TSGs mutate Normally encode proteins that inhibit cell division or initiate apoptosis In the absence of these proteins cell division proceeds uncontrollably and cell death is absent If the p53 gene mutates then the p53 protein can no longer function properly Mistakes in DNA replication are not repaired leading to an increase in the accumulation of mutations And apoptosis does not occur Disastrous TSGs also encode repressors that prevent RNA poly from transcribing a gene Self stimulatory not supposed to have them Nonfunctional p53 protein Damaged DNA is not repaired or Apoptosis is absent Mutations accum Immortal 5 Telomerase is active Allows cells to divide forever They become immortal 6 angiogenesis Telomerase repairs the telomeres after each cell division Formation of new blood vessels to supply nutrients and oxygen to developing tissue Cancer cells regain the ability to produce vascular endothelial growth factor VEGF VEGF promotes the growth of blood vessels 7 metastasis Cells move into the bloodstream or lymphatic vessels to make new tumors at distant sites from the primary tumor A caner that has this ability is malignant A benign tumor encapsulated with connective tissue and is non invasive Causes of Cancer Heredity Cancer is not inherited but one can inherit a predisposition for cancer Certain alleles have been linked to cancer Individuals who inherit those alleles is at a greater risk Ex BRACA1 BRCA2 p53 Radiation UV rays X rays Organic chemicals TAR HRT Pollutants pesticides toxins asbestos Viruses HPV Oncology study of cancer Carcinomas cancers of the epithelial tissues colon Adenocarcinomas cancers of glandular epithelial cells thyroid Sarcomas cancer of muscle and connective tissues bone Leukemias cancers of the blood WBC Lymphoma cancers of lymphatic tissue lymph nodes spleen Signs of Cancer Change in bowel or bladder habits A sore that does not heal Unusual bleeding or discharge Thinking or lump in breast or elsewhere Indigestion or difficulty swallowing Obvious change in wart or mole Nagging cough or hoarseness Detecting skin cancer a Asymmetry b Border is irregular c Color varies from one area to another d Diameter is larger than 6 mm Testing for cancer Genetic testing can determine if an individual has inherited genetic mutations to a pronto onco gene of TSG Much the same as knowing family medical history Tumor marker tests blood tests for tumor antigens antibodies CEA antigen can be detected in someone with colon cancer PSA test for prostate cancer Traditional treatments Surgery Removal of cancerous tissue Radiation therapy X rays or gamma rays are administered with a laser beam Causes breaks in DNA too large to repair Drugs that inhibit DNA replication or disrupt mitotic spindle formation Chemotherapy Kills good cells too Side effects Hair loss Nausea Fatigue Future treatments Anti angiogenesis out the cancer P53 gene therapy In clinical trials Administer anti angiogenesis factors to inhibit blood vessel growth and essentially starve Retrovirus is injected into the body to deliver the healing p53 gene to cancer cells Once the p53 gene is expressed it will trigger apoptosis of the cancer cells Immunotherapy 1 Genetically engineer antigen presenting cells APCs APCs present forgien antigens to cytotoxic T cells The activated t cells then destroy the cells expressing the foreign antigen APCs can be genetically engineered to express an antigen specific tot the tumor so that only the tumor cells are targeted by the immune system Design killer antibodies Antibodies are designed to kind to tumor specific antigens The antibodies have the chemotherapeutic drug attached that will effect the cancer cells
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