Bio 160 Week 8 DNA for NOONAN
Bio 160 Week 8 DNA for NOONAN Bio 160
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This 5 page Class Notes was uploaded by Alex on Sunday October 16, 2016. The Class Notes belongs to Bio 160 at University of Mississippi taught by SYMULA, REBECCA E in Fall 2016. Since its upload, it has received 2 views. For similar materials see Biological Sciences I in Biology at University of Mississippi.
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Date Created: 10/16/16
Bio- DNA NOONAN CLASS If you were in Symula’s class the beginning of the fall semester of 2016, then you should NOW HAVE NOONAN. NOT SYMULA. SYMULA IS TEACHING THE JONES’ CLASSES NOW. YOU SHOULD HAVE NOONAN. Noonan uses his SLIDES to make his test. He will not TOUCH the textbook Nucleic acids code for biological information o DNA contains genetic information o RNA makes proteins o Protein and lots of DNA were present when you were conceived as a zygote o DNA is used to make DNA and RNA (transcription). RNA is used to make proteins (translation) DNA RNA Proteins transcribe translat DNA carries information in a double helix o DNA sequences are strings of nitrogenous bases with a particular and specific order. This is what holds genetic information. It’s like typing words on a paper, the letters go in a specific order to give information (like these notes) o DNA is double stranded, has the deoxyribose sugar, and contains thymine o RNA is single stranded, has ribose sugar, and contains Urucil. o You have two of each chromosome, one from your mom and one from your dad o These chromosomes are double stranded o The two parts of one chromosomes are complimentary o Complementary base pairing- each base has a certain other base it goes with. Ex C (cytosine) is always paired with G (Guanine) o Replication- the replication of DNA, the entire molecule o Transcription- making RNA from DNA. We make a new nucleic molecule o We take two strands and make one strand There are four key features that define DNA structure o The “blue” or backbone of DNA is made up of the sugar and phosphate group. o Hydrogen bonds between the bases hold the strands together. o Double helix with uniform diameter o It is right handed- referring to how your fingers curl in your hand – I suggest looking up an image o The strands are antiparallel- very important. Questions on the test will relate to this o Is has major and minor grooves- factoid Complementary base pairing determines DNA diameter o Remember, the diameter is uniform. It is uniform because we always pair A-T and C-G o A and G have two circles of carbon and C and T have only one. The reason they are paired is to keep this diameter Chargaff’s rule is related to complementary base pairing o A=T o C=G o Chargaff went to a butcher shop and studied, chemically, the structure of DNA. He observed that A and T were of the same amount as well as C and G, coming to the conclusion of the base pairing Watson and Crick summarized preexisting cells o Xray crystallography pictures of DNA helped to discover the structure of DNA DNA is right handed The two DNA strands run in opposite directions o Antiparallel- parallel, but situated in opposite directions o The sugar molecules have a number of carbons. These carbons are numbered. 5 3 o It is ordered in a 3 to 5 carbon order o The strands are running in opposite directions o That means one side, the top is the 3 carbon and the bottom is the 5 carbon while the other strand, the top is 5 and the bottom is 3 o For replication, you have “open” the DNA o When we are copying, this antiparallel order is confusing The helix has two grooves DNA structure is essential to its function o The organization of bases in sequence determines everything that you are. o It is CRITICAL How does a double helix replicate o Semiconservative- when you break apart the two strands and replicate the second one to create two o Conservative- when you simply copy from the first (DOES NOT HAPPEN) o Dispersive- when you copy different bits and pieces of DNA until you have two complete helixes Meselsonn and Stahl showed that DNA replicates semi-conservatively o They took DNA in a flask and pull DNA out of bacteria. o Then they put it into a matrix, like a gel, onto which they put it in a subfusion and it spins around o The DNA falls down to the bottom o Then, the DNA will try to go through the matrix o Then, they took the bacteria and put them in a solution where they can replicate o In this solution, they made sure that the only nitrogen that was available was a light isotope. o Then, they did the same thing with the other DNA, and saw that the band was a lot lower but also, there’s another band near the top o Because the DNA with the light isotope is lower than the top band, the unzip of the DNA was made with the light nitrogen with the heavy nitrogen. So, half of the DNA was heavy and light DNA when then continue to replicate o From this experiment, they concluded that you start with one heavy strand, it’s unzipped and another strand is made with the light. Then, it’s unzipped again to make a set of all light nitrogen and half heavy, half light again, eventually creating lighter DNA until it is the most common. DNA replication involves 2 steps o Strand separation (you need to open a book to be able to copy it) o Extension or elongation o Coloration is used to represent new and old – old is blue, red is new Strand separation opens the helix with specific enzymes o DNA is double stranded because it needs to be more stable o Helicase- an enzyme that “unzips” the DNA molecule by breaking the hydrogen bonds. o Single-stranded binding proteins attach to the DNA that was pulled apart to keep them apart so the strands don’t come back together o These single stranded proteins are made when the cell knows it is going to divide DNA extension adds nucleotides to the free 3’ OH *** 20:20 o Phosphodiester bond between phosphate and sugar o Hydrogen bonds between bases hold the DNA together o The pulled apart strands have nucleotides added onto them sepearated strands o Like question on test! Copy 5’-GCATC-3” You have to go 3’ to 5’. Add the nucleotides to the 3’ end. So you would go left to right 5’-GCATC-3’ TAG-5’ You do it off of the new strand you’re making. NOT THE ORIGINAL o The original strand that you are copying is called a template strand Enzymes add nucleotides to the free 3’ OH o Polymerase- an enzyme that creates new DNA o They grab nucleotriphosphates and add them to the DNA. Two leave and a base comes and sits with it dNTPs are substrates for DNA polymerase SLIDE LOOK UP DNA polymerase needs a free 3’OH group o It must find the end to copy o It grabs around the strand and goes down, pulling in dNTPs o It is a large enzyme o There are many different polymerases o They create new strands of DNA, RNA, or they “spell check” to proofread the DNA Extension starts with a “primer” o Polymerase NEEDS a free 3’ carbon at the END o Because of this, we have to have an RNA polymerase to begin the process o Primase comes in and sticks on a few dNTPs o The polymerase then “sees” the free 3’ carbon and continues to replicate DNA polymerase recognized the 3’ OH on the primer o LOOK AT SLIDE FOR PIC o The polymerase “chases” the helicase The leading strand replicates continuously o The newly synthesized DNA is ALWAYS 3’to 5’ o Template is 5’ to 3’ o We MAKE DNA from 5’ to 3’ (template!) o We READ it from 3’ to 5’ (read=NEW STRAND) o The top strand that begins with 3’ goes along the template easily o The bottom one that starts with a 5’ has to go to the opposite direction. Once it replicates a part of it, the helicase is further down the DNA, opening up more DNA the lagging strand replicates in fragments o you cannot rip the strands apart and go from end to end. It is way too long o primase comes in and starts off the lagging strand so there is a free 3’ OH for polymerase to begin off of o okazaki fragments- discontinuous fragments in the lagging strand that is not connected DNA polymerase removes RNA primers and DNA ligase patches new DNA o There are ‘chunks’ of RNA in the lagging DNA (the sections put on by the primase) o another polymerase pulls it out and then the original polymerase has another 3’ and so completes and attaches the two fragments together o DNA ligase- an enzyme that glues together the new and old strands Enzymes can make mistakes o Proofreading enzymes- the error rate is very low o Our cells have one or two mistakes even though it is 1 in a million chance….there are MILLIONS of DNA strands o You do not catch all of mistakes- as we age we get genetic diseases (cancer is an example) PCR is a controlled method of replicating DNA o It takes the same ingredients that our cells use to copy DNA and copies portions of DNA and makes copies off of it o This is put in a tube Primers are added and dNTPs and polymerases Then they go through the process just like it would in real life Watch youtube vid on PCR
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