DNA & Gel Electrophoresis Guilford County Sci Vis V205.05

The Structure of DNA

DNA  Deoxyribonucleic acid  Large molecule called a polymer Polymer means molecule with many units  Units or monomers of DNA are nucleotides

Nucleotides  Made of 5-carbon sugar called deoxyribose  Deoxyribose contain a phosphate group and one of four nitrogen bases  4 nitrogen bases A for adenine G for guanine C for cytosine T for thymine

Purine Bases  Adenine and guanine  The larger of the 2 types of bases  Have a double ring structure Adenine Guanine

Pyrimidine Bases  Cytosine and Thymine  Have a single ring structure Cytosine Thymine

Deoxyribose sugar  3 oxygen and 5 carbon atoms which make up the DNA “backbone”  The hydroxyl groups’ carbons link to phosphates to form this “backbone” dAMP: Deoxyadenosine monophosphate, a nucleotide containing adenine, a 2'-deoxyribose sugar and phosphate, part of DNA structure. dCMP: Deoxycytosine monophosphate, a nucleotide containing cytidine, a 2'-deoxy sugar, and phosphate, part of DNA structure.

Double Helix  DNA is composed of twisting strands of nucleotides  Each strand is a helix or spiral staircase  2 strands are bound together to create a double helix Double helix

Configuration of DNA  A & T always join together and form 2 hydrogen bonds  C & G always join together and form 3 hydrogen bonds  Think A & T and UNCG to remember these.

DNA Fingerprinting

Definition  Method of identification that compares fragments of DNA  DNA is the genetic material found in the cell nucleus  DNA of each individual is unique, with identical twins being the only exception

Constructing a Fingerprint  A “fingerprint” is constructed by Obtaining a DNA sample from body tissue or fluid Cutting this sample into pieces using enzymes Arranging these pieces using gel electrophoresis

Gel Electrophoresis  Refers to the forced movement of molecules by electricity  Separates macromolecules (large molecules) on the basis of size, electric charge, and other physical properties.  The gel is like Jell-o.  Electrophoresis describes the moving of the charged DNA Electro: energy of electricity Phoros: to carry across

Steps in Gel Electrophoresis  Holes created in gel to hold DNA solution  DNA solutions loaded into holes  Gel is “excited” by electricity and small molecules move through the gel  Photograph is taken to save the results of the fingerprint  2 matching fingerprints indicate they are probably from identical sources

Uses of fingerprinting  Discovery of genetic causes of diseases  Mapping the human genome (2003)  Forensic science  Paternity testing

References  Adenine and guanine - nucleicacids.htm nucleicacids.htm  Thymine and cytosine - nucleicacids.htm nucleicacids.htm  dAMP & dCMP -

References  Double helix - s/double-helix.jpg s/double-helix.jpg  A&T logo –  UNCG logo –