Lecture 4 Cells DNA Gene mutations Griffith s transforming factor hypothesis material in dead bacterial cells can genetically transform living bacterial cells conclusion a chemical substance from one cell is capable of genetically transforming another cell Anatomy of the cell The cell and genes Genes segments of DNA instructions Packaged into chromosomes The complete set of instructions is called the human genome There are 22 pairs of chromosomes plus 1 pair of sex chromosomes DNA replication DNA transcription mRNA translation protein RNA polymerase is the enzyme responsible for transcription Ribosome is the enzyme responsible for translation DNA linear polymer of repeating nucleotide monomers Unit of info genetic word codon Letters are A T G C In RNA T is substituted to U 3 nucleotides 1 codon word 1 amino acid each letter is a nucleotide base and each word represents a codon DNA mutations they change one piece of DNA sequence Genetic code substitution deletion addition Normal cell division if there is a mistake a normal cell will kill itself apoptosis Cancer cell division apoptosis doesn t work so keeps replicating messed up cell Mutated genes in cancer 2 1 oncogenes normal proto oncogenes or viral oncogenes tumor suppressor genes cancer 3 DNA repair genes progress to cancer Proto oncogenes contribute to uncontrolled cell proliferation and lead to cancer Arise from absence contribute to uncontrolled cell proliferation and mutations in DNA repair genes may prevent mismatch repair and can It can become an oncogene after mutation or increased expression Proto oncogenes code for proteins that help to regulate cell growth and differentiation Normal gene that allows normal cell growth normal regulation of growth Oncogenes accelerate cell growth division Oncogenes are mutated proto oncogenes that have been integrated into a cell s Family of normal genes that instruct cells to produce proteins that restrain cell growth and division They are the checkpoints Since tumor suppressor genes code for proteins that slow down cell growth and division the loss of these proteins allows a cell to grow and divide uncontrollably Code for proteins whose function is to correct errors Mutations in DNA repair genes failure in repair which allows mutations to accumulate Xeroderma pigmentosum people with this condition have inherited a defect in a DNA genome Tumor suppressor genes DNA repair genes repair gene Time Mutation inactivates suppressor gene cells proliferate mutations inactive DNA repair genes proto oncogenes mutate to onco genes more mutations genetic instability
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