Prophase Metaphase Anaphase

There were originally three separate theories of how DNA Replication could have occurred. Meselson and Stahl eventually proved that DNA Replication was replicated semi conservatively, through their famous experiment involving E. coli. As many generations of E.coli are allowed to replicate, the DNA they contain is composed of more N 14 than N 15. This shows up as a different band in the test tube, due to the heavier weight of the N 15 as compared with N 14.

Your task – To use a vine to explain the role of the enzymes in DNA Replication You must create one Vines to explain the basics of the process of DNA Replication Your Vine must include the following: Tag for Vine - #profbio DNA Helicase RNA Primase DNA Polymerase III DNA Polymerase I DNA Ligase All enzymes must be labeled and the process must result in the formation of two strands of DNA produced semi-conservatively. +

Your task – To use a vine to explain the role of the enzymes in DNA Replication You must create two Vines –One for the lagging strand - One for the leading strand Your Vines must include the following: Tag for Vines - #profbio DNA Helicase RNA Primase DNA Polymerase III DNA Polymerase I DNA Ligase All enzymes must be labeled and the process must result in the formation of two strands of DNA produced semi-conservatively. +

Sanger Sequencing – a method of determining the exact sequence of DNA in an organism. Dideoxynucleotides result in the termination of a DNA sequence. Sanger used this to determine the sequence of DNA by the following: -DNA Replication is performed on a sequence of choice many times times using Dideoxynucleotides. (One set for A,T,G,C) -This revealed the last base in each of the sequences. -Then the sequences are overlaid on top of one another, and you can see each of the bases in a specific set of nucleotides. Check out this animation to see the process in action.

Short Tandem Repeats (STRs) are short sequences of DNA contained in the highly repetitive sequences that differ greatly between individuals. Since there is a high amount of variance between these sequences in individuals, they can be used with relatively high efficacy to match suspect DNA to samples found at a crime scene. Comparisons of the lengths of these STRs are useful in DNA Profiling. See if you can see the differences between Bob and Anne’s STRs in the diagram to the right.

DNA Profiling Compares sections of DNA between individuals in order to determine paternity or relationships, as evidence in criminal cases or to identify species. Through gel electrophoresis, fragments of DNA are moved through an electric field and separated based on their size. 1. DNA samples are taken and amplified with PCR. 2. Restriction enzymes cut DNA into fragments at Short Tandem Repeats in each sample. 3. A fluorescent marker binds to the repeats in the DNA fragments, so that results can be seen. 4. Samples are added to a gel electrophoresis chamber. Electric current is passed through, pushing the fragments along. 5. Heavier fragments stay closer to the origin and smaller fragments go further. 6. A banding pattern shows up for each DNA sample and can be compared. Animation from Learn.Genetics: Animation from Dolan DNA Learning Centre::

Images from Dolan DNA Learning Centre::

DNA Profiling in forensics DNA Profiling can be used to identify suspects from trace DNA evidence. It can also be used to eliminate the innocent from the investigation. In this case, a hair follicle was left at a scene of a crime. Who was the perpetrator? A = trace evidence B = homeowner C = suspect 1 D = suspect 2 ABCD

DNA Profiling in forensics DNA Profiling can be used to identify suspects from trace DNA evidence. It can also be used to eliminate the innocent from the investigation. In this case, a hair follicle was left at a scene of a crime. Who was the perpetrator? A = trace evidence B = homeowner C = suspect 1 D = suspect 2 ABCD Explanation: We expect 100% match as the cells left behind are the perpetrator’s own cells.

Gel Electrophoresis Lab 1.Load samples from each of the microtubes in to the wells. 2.Load the gel into the electrophoresis apparatus with the positive end at the far end of the gel. 3.Place the lid on the apparatus, and connect the cables to the correct part of the power source. 4.Wait 10 minutes. 5.Disconnect the power source, remove top of apparatus. 6.Remove gel and place on a white surface to record data. 7.Identify the suspect that was present at the scene of the crime, based on the bands present in the gel. S1 S2 A B C Sample Gel Set Up

So, how can scientists use this information about how DNA replication works? POLYMERASE CHAIN REACTIONGENE TRANSFER From: png From: cornerstone-of-molecular-biology-the-pcr-reaction/

Polymerase Chain Reaction Used to amplify small samples of DNA In order to use them for DNA profiling, recombination, species identification or other research. The process needs a thermal cycler, primers, free DNA nucleotides and DNA polymerase. 1. Heating in the thermal cycler denatures hydrogen bonds, exposing bases. 2. The mixture cools. Primers are added to the start of the target genes. 3. DNA Polymerase replicates the DNA using complementary base pairing. 4. This cycle is repeated many times, until there are thousands of copies – enough to amplify even tiny samples found at a crime scene! Animation from McGraw Hill: Animation from DNAi.org:: You do not need to know details of this method, but can you see how the technology has mimicked the natural process of DNA replication?

Genetic Engineering Also known as genetic modification, gene transfer or transgenics. We already make use of gene transfer in industrial production of insulin: All living things use the same bases and the same genetic code. Each codon produces the same amino acid in transcription and translation, regardless of the species. So the sequence of amino acids in a polypeptide remains unchanged. Therefore, we can take genes from one species and insert them into the genome of another species. “The Genetic Code is Universal” restriction