What we already know: The nucleus contains DNA Eukaryotes have linear DNA Prokaryotes have circular DNA DNA is copied during Interphase of the Cell Cycle

What we already know: Traits are distinguishing features or characteristics Traits are passed from parent to offspring Traits are passed on through genes Genes are specific sections of DNA In sexual reproduction, offspring get half of their genes from each parent

DNA is INFORMATION DNA= deoxyribose nucleic acid A molecule that stores information Contains the instructions for making proteins Like a cookbook contains the instructions for making a cake

Proteins and Amino Acids Proteins are large molecules made up of chains of amino acids There are 20 different amino acids that combine into thousands of different proteins Folding of the string of amino acids is critical for protein function

Proteins and Amino Acids Proteins can vary in size from just 20 amino acids, like this one found in Gila Monster saliva… To this protein nicknamed “Titan” with 34,350 amino acids, found in human muscle tissue

Check for Understanding: What is the relationship between proteins and amino acids? What is a trait? When is DNA copied? What is a gene?

Check for Understanding: What is the relationship between proteins and amino acids? 20 amino acids come together in various combinations to make proteins What is a trait? Distinguishing features or characteristics When is DNA copied? During Interphase of the Cell Cycle What is a gene? A specific section of DNA that contains the code for a protein

DNA & The Genetic Code DNA molecule is shaped like a twisted ladder The molecule is formed from nucleotide subunits that consist of: Phosphate Sugar (Deoxyribose) Nitrogen Base

DNA & The Genetic Code The side rails of the ladder are formed by the sugar-phophates The rungs of the ladder are formed by two bases coming together There are four different bases in DNA Adenine Thymine Cytosine Guanine All Tigers Can Growl

Some comic relief…

DNA Structure Video

DNA & The Genetic Code The sequence (order) of bases in a strand of DNA makes the code for building proteins The genetic code is a “triplet” code meaning that every three bases codes for one amino acid A gene is the entire sequence of bases that codes for a specific protein Like a recipe for a specific dish

Replication of the DNA Replication is the copying of DNA 1. Two strands separate 2. Free-floating nucleotides match up with the nucleotides on each strand 3. Two identical molecules of DNA are made

Watch Replication in Action This movie shows a computer animation of how DNA is replicated Another video on YouTube

Check for Understanding What three components make up the nucleotide subunit? What are the four bases and what is the rule about how they pair together? Describe what is meant by a “triplet code.” What are the steps of DNA replication?

Check for Understanding What three components make up the nucleotide subunit? Phosphate, Sugar, Nitrogen Base What are the four bases and what is the rule about how they pair together? Adenine pairs with Thymine Cytosine pairs with Guanine Describe what is meant by a “triplet code.” Three bases code for one amino acid What are the steps of DNA replication? 1. Strands separate 2. Nucleotides pair up 3. Two identical strands are made

A HISTORY OF DNA (1928) Frederick Griffith Discovers that a “transforming factor” changes harmless bacteria into deadly bacteria (1952) Rosalind Franklin Takes x-ray photographs of DNA (1953) James Watson and Francis Crick Use Franklin’s images to describe the structure of DNA (1962) Watson, Crick, and Wilkins win the Nobel Prize, Franklin has already died from cancer (1958) so she does not get recognition