DNA The Secret of Life
Deoxyribonucleic Acid • DNA is the molecule responsible for controlling the activities of the cell • It is the hereditary molecule • DNA directs the production of protein
Structure of DNA • In 1953, Watson and Crick proposed that DNA is made of two chains of nucleotides held together by nitrogenous bases. • Watson and Crick also proposed that DNA is shaped like a long zipper that is twisted into a coil like a spring.
Structure of DNA • Because DNA is composed of two strands twisted together, its shape is called double helix. • A double helix resembles a twisted ladder.
Nucleotides • DNA is made up of subunits called nucleotides • Nucleotides consist of the backbone, which is made of sugar (deoxyribose) and phosphate, as well as a nitrogenous base
Nucleotide Nitrogen base Phosphate Sugar
How Did DNA Get its Name? • Based on what you just learned, how do you think deoxyribonucleic acid (DNA) got its name?
Nucleotides • A nitrogenous base is a carbon ring structure that contains one or more atoms of nitrogen. • In DNA, there are four possible nitrogenous bases: adenine (A), guanine (G), cytosine (C), and thymine (T). Cytosine (C) Guanine (G) Thymine (T) Adenine (A)
Nucleotide Sequence • The four nucleotides are represented by the first letter in their name • A – Adenine • G – Guanine • T – Thymine • C – Cytosine
Nucleotide Sequence • In DNA, Adenine always pairs with Thymine • Cytosine always pairs with Guanine
Nucleotides • Nucleotides stack on top of one another forming the double helix, or twisted ladder
DNA Building • Click here to link to a DNA building activity online!
Go Get It Moment! • When you hear “Move it!” you will have 30 seconds to come get one piece of paper with an A, G, T, or C on it. • Then find someone else in the room whose letter correctly matches with your nucleotide letter and stand by that person. • What are the questions? • “Move it!”
Go Get It Moment! • When you hear “Double Helix”, you will have 1 minute to make a classroom DNA strand by standing next to another pair of nucleotides • What questions are there? • “Double Helix”
DNA Replication • In order for cells to divide, DNA must be able to make exact copies of itself • This process is known as DNA Replication
DNA Replication • DNA Replication occurs before mitosis and meiosis • Replication results in two identical DNA daughter strands from one mother strand
Process of DNA Replication • The DNA strand is unzipped at the hydrogen bonds by an enzyme named helicase. • Nucleotides in the nucleus then find their corresponding nucleotides on each of the two open DNA strands and produce two new DNA double helixes.
Link to DNA Replication Animation • Click here to see how DNA Replication works
Protein Synthesis • The main job for DNA is to direct the production of protein • Protein makes tissues and organs and carries out the organism’s metabolism • Proteins are polymers (chains) of amino acids
Protein Synthesis • The sequence of nucleotides in each gene contains information for assembling the string of amino acids that make up a single protein