DNA & Gel Electrophoresis

Guilford County Sci VisV205.05

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 - http://

www.chemsoc.org/networks/learnnet/cfb/nucleicacids.htm

Thymine and cytosine - http://www.chemsoc.org/networks/learnnet/cfb/nucleicacids.htm

dAMP & dCMP - http://www.cancerwatch.org/glossary/glossary_7.cfm

References Double helix -

http://alum.mit.edu/ne/opendoor/200507/images/double-helix.jpg

A&T logo – www.ncat.edu UNCG logo – www.uncg.edu