Bsc103 week 5
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This 8 page Class Notes was uploaded by Kierra Thompson on Sunday September 25, 2016. The Class Notes belongs to 103 at University of Southern Mississippi taught by Emily Clark in Fall 2016. Since its upload, it has received 3 views. For similar materials see Biology & Society in Science at University of Southern Mississippi.
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Date Created: 09/25/16
BSC 103 Week 5 Playing With DNA to do handy things Dna contains the instruction manual to make the proteins your body needs Every structure has a unique sequence Many many applications o Crime scenes o First used to solve a crime in 1986 Present in almost every cell in your body How we go from evidence to a solved case o Need a sample that has the suspect’s DNA o Extract samples from the DNA o Amplify using the Polymerase chain reaction A laboratory technique that replicates a certain DNA The Polymerase Chain Reaction Laboratory technique used to replicate and amplify a specific DNA segment Primers: short segments of DNA that guide DNA polymerase to the section of DNA to copy 3 main steps o Heat to separate the strands o Anneal primers o Elongate strands Allows dna replication to occur many times Can make billions of copies from a starting sample or just a few molecules of DNA After Pcr, we create DNA profiles Dna take profiling adavantage of the fact that no two people have the exact same DNA sequence or genome…each person has a unique DNA” fingerprint” o Genome: One complete set of genetic instructions encoded in the DNA of an organism DNA profiling we could sequence the whole genome from cells found at the scene, as well as from suspects. Shortcut o Use prc to amplify only specific segments of DNA (Short tandem repeats (str)) STR and DNA profiling Strs are sections of a chromosome in which DNA sequences are repeated o Sequence AGT may be repeated over and over again Everyone has STRs that are located in the same place among the chromosome o the exact length of STR varies from person to person How does this process play out? Collect cells and extract DNA Use PCR to amplify multiple STR regions Separate STRs using gel electrophoresis o Laboratory technique that separates fragments of DNA by size Separated fragments of DNA create a specific pattern of bands Visible using fluorescence Banding pattern is unique to each person Different individuals have different DNA banding patterns…so compare to find the bad guy knowing the structure of DNA, and also that DNA sequences vary between individuals, as well as how it replicates, helped us catch criminals. We also know that proteins are made from it….could this be useful? o Yes to make hybrid genes Take coding part of a gene from one species, and put it behind the regulatory part of a gene from another species Results recombinant genes Transgenic Organism Organisms that carry one or more genes from a different species Carries recombinant genes Examples o GMO genetically modified organisms An animal or plant that has been created through genetic engineering Advantages of GMO For crops, you can engineer plants that are naturally resistant to common pests o Help avoid using potentially hazardous food o Higher crops yield using less land For animals, like salmon, you get fish that grow larger and faster, and are cheaper to produce o This provides nutritious food for people who may not be able to afford wild salmon o More food for an ever growing population Disadvantages of GMO Lack of long term studies about the health consequences o Allergenicity o Gene transfer of antibiotic-resistance traits Few studies examing the environmental impact of GM organism on natural population o What happens when GM organisms breed with wild organisms? What else is handy to understand how DNA codes for protein? When you want to cure previously incurable diseases Gene therapy o Gives patients a healthy version of a defective gene Remember, a “defective” gene means you produce a protein that doesn’t function properly. o You inactivate a virus, and insert the gene of interest. o You take advantage of the fact that viruses know how to get into cells, and that they hijack YOUR cellular machinery to replicate their genetic material. Severe combined immunodeficiency o Bubble boy disease o Produce a defective common gama chain protein Mutations, mitosis, and uncontrolled cellular division During DNA replication, DNA polymerase brings complementary nucleotides to form new strands o Every time this happens, DNA polymerases have to bring about 6 billion nucleotides in the right order. DNA polymerase make a mistake 1 per every 100,00 nucleotides o With 6 billion, that’s 120,000 mistakes everytime a cell divides Luckily, DNA replication comes with proofreading mechanism o Repair enzymes fix most of these mistakes o If mistake is too big, cells undergo apoptosis which is self- destruction When error is not caught or repaired incorrectly o Changes in the nucleotide sequence; mutations that remain after mismatch repair become permanent after the next round of cell division o Mutations give rise to alleles, which are variant forms of a gene Two alleles of one gene are often very similar to one another only differ by a few nucleotides Birth of Mutation and Perpetuation Mutagens Induce mutations Include any chemical or physical agent that can damage DNA by changing its nucleotide sequence If the mutagen causes cancer, it’s a carcinogen Mutations can also be inherited Some mutations have the potential to cause bigger headaches than others Base substitution o Simpliest o Swapping of one nucleotide for another during DNA replication Missense mutation o Altered codon results in the wrong amino acid getting inserted into the protein Nonsense mutation o Altered codon prematurely ends synthesis of the protein Silent mutation o Altered codon codes for same amino acid as original (genetic code is redundant) Insertion mutation o An extra nucleotide is added to the replicating strand Delete mutation o Nucleotide is omitted to the replicating strand Frameshift mutation o Insertion and deletion mutations o result in the complete alteration of the amino acid sequence of a protein. If the number of nucleotides that are inserted or deleted is not a multiple of 3, then the reading frame is shifted. This is because the ribosome reads nucleotides in groups of three (codons). Most mutations are neutral Either make no change in the expression of any gene or the changes does not affect the function of any gene product Mutations are necessary, as they generate genetic variation, i.e. they provide the raw material on which selection can act. While some mutations will negatively affect an organism, some will allow it survive better under certain environmental conditions. Some mutations are definetily bad o Wrong DNA sequence can mean defective proteins o Mutations that occur in proteins that regulate cell division can be problematic o Cancer A disease of unregulated cell division Mutations that occur in proteins Cell Divison the process by which a cell reproduces itself needs to happen in an ordered sequences of stages o cell cycle includes preparatory and division phases How do cells divide? Interphase preparatory phase o Cell spends most of life in interphase o Copy cellular contents o Duplicate organelles, DNA and cytoplasm o Ensures each new cell has the same amount as original cell o Includes three phases: G1, S, G2 G1 phase cell grows, make extra cytoplasm S phase dna replication occurs results in identical sister chromatids G2 phase cell prepares for division Ready for Division Division stage consists of two steps o Mitosis Segregation and separation of duplicated chromosomes during cell divison o Cytokinesis Daughter cells physically split from each other Mitosis o 1 phrophase Chromosomes condenses, nuclear envelope dissolves o 2 metaphase sister chromatids line up in the middle o 3 Anaphase Sister chromatids are physically separated o 4. Telophase Identical chromosomes now present at each pole Nuclear envelope reforms Cytokinesis o Enlarged cell split into two cells o Each has full complement of DNA o One parent cell thus yields two daughter cells Mitotic spindle o Structure that seperates sister chromatids during mitosis Made of microtubules Hollow protein fibers Key components of cytoskeleton Attach to the centromere on chromosome Cancer cells have damaged check points o Divide when they should not o DNa damage, and /or erroneous chromosomal separation are pressed to daughter cells
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