DNA – The molecule of Heredity Chromosome - Carrier of genetic material, a long strand of coiled DNA Gene – a segment of DNA found on a chromosome 1 gene = code to make 1 polypeptide (protein) What is DNA? A molecule, Deoxyribonucleic Acid, that holds the master copy of an organism’s genetic code.

DNA – The molecule of Heredity What is DNA? Deoxyribonucleic Acid, Who Discovered the structure of DNA? Click here for video onDNA Watson and Crick – 1953, discovered that DNA was made of two spiral strands, they called it a double helix. Why is DNA important? Knowledge of DNA is critical for understanding… Birth Defects Cancer Genetic Engineering Viral Diseases Aging Criminal Investigation

DNA – The molecule of Heredity What are the building blocks of DNA? - Subunits called Nucleotides make up DNA. Nucleotides are made up of: A simple sugar – deoxyribose A phosphate group A nitrogen base (one of four) Adenine (A) Thymine (T) Cytosine (C) Guanine (G)

A Closer Look at DNA Untwisted The 2 strands are held together by a weak hydrogen bond. The 2 strands are held together at the nitrogen bases. Adenine will bond with Thymine Cytosine will bond with Guanine These are called complimentary base pairs Deoxyribose Sugar Hydrogen Bond Covalent Bond Phosphate Group Covalent Bond

DNA Replication What process have we already discussed that involves DNA Replication? The Cell Cycle!!!!!!!!!! (more specifically, interphase!) Remember… DNA needs to replicate so that when the cell divides in half, the two daughter cells will have the same genetic information!

DNA Replication DNA untwists

DNA Replication 2. Two chains unzip or separate

DNA Replication 3. Free floating nucleotides in the nucleus bonds to the unzipped strands by base pairing with the help of enzymes.

DNA Replication 4. Two identical DNA molecules are formed.

DNA Replication - RECAP Process: DNA untwists DNA unzips and separates Free floating DNA nucleotides in the nucleus come and bond to the unpaired strands of DNA. 2 identical DNA molecules are formed Product: 2 DNA molecules that are exactly alike. **Replication is Semi-Conservative – meaning that the 2 old DNA halves are used as patterns on which to build to new halves.

DNA Replication Active Art Active Art Clip of DNA Replication

Double or Single Stranded What is RNA? RNA strands for Ribonucleic Acid Differences in RNA and DNA: DNA RNA Double or Single Stranded Double Single Nitrogen Bases Thymine Uracil Sugar Deoxyribose Ribose RNA is used in the processes of transcription and translation. There are 3 different types of RNA. RNA Function mRNA – messenger RNA A copy of DNA. Takes information from the nucleus to the ribosome. tRNA – transfer RNA Transports amino acids to the ribosome to be assembled into a protein rRNA – ribosomal RNA Makes up the ribosome; assembles proteins

We know that DNA is very important because it gives our bodies instructions to make proteins. But how does it do that??? To go from DNA  proteins, DNA must first become RNA and then go through several processes to become a protein.

How does DNA turn into RNA and then make a protein????? This happens through a process called protein synthesis. Protein synthesis is made up of 2 main parts: Transcription Translation

Let’s look at what we know about proteins so far… Proteins are made up of amino acids. Proteins are in our foods, such as meats. Enzymes are a type of protein. Antibodies are a type of protein. Considering all of that, we have already learned that proteins are pretty important. Therefore, our DNA must be pretty important too!

Transcription Transcription: Making a copy of mRNA from DNA mRNA (messenger RNA) = A copy of DNA. Takes information from the nucleus to the ribosome. Transcription takes place in the nucleus of the cell! Practice: DNA TAC CGA GTA ACT mRNA AUG GCU CAU UGA

Transcription DNA untwists

Transcription 2. Two chains unzip or separate

Transcription 3. Free RNA nucleotides pair with complementary DNA nucleotides on one of the DNA strands.

Transcription 4. mRNA breaks away as the DNA strands rejoin

Transcription - RECAP Process: DNA untwists DNA unzips and separates Free floating RNA nucleotides in the nucleus come and pair with their complementary DNA pair. The mRNA breaks away and the DNA comes back together. Product: 1 single-stranded mRNA molecule The same double-stranded DNA molecule that you started with. Transcription video

Translation Translation: converting the mRNA message into a sequence of amino acids to form a protein tRNA (transfer RNA) = brings the amino acid to the ribosome Each tRNA carries only 1 amino acid! Translation takes place at the ribosomes in the cell! Codon = 3 nitrogen bases on DNA or mRNA. Each codon represents 1 of 20 amino acids. START CODON – AUG codes for the amino acid Methionine and starts protein synthesis Anticodon = 3 bases on tRNA that bond to the codon of mRNA Remind students that we already know that ribosomes help make proteins and that proteins are made up of amino acids.

Translation mRNA attaches to the ribosome

Translation 2. tRNA anticodon pairs with mRNA

Translation 3. Amino Acids are joined together with peptide bonds to make a protein.

Translation – RECAP Process: mRNA attaches to the ribosome tRNA anticodons pair with mRNA Amino Acids are joined together with peptide bonds to make a protein. Product: Protein!!!!!!!!!! (determined using a codon chart) Video on translation

How can I tell which codons are used to make the protein? Codon Chart

Protein Synthesis – RECAP

Replication and Protein Synthesis Web Activity http://www.pbs.org/wgbh/aso/tryit/dna/ 

If the order of bases change Genes will change Just like everything else in our bodies, there is a chance that this process will mess up. When replication, transcription or translation mess up, we call it a mutation. If the order of bases change Genes will change Trait will be expressed differently

Mutations Mutation – any mistake or change in the DNA Sequence, both random or from radiation/chemical exposure (only changes in the gametes will be passed on from parent to offspring) Types of Mutations: GENE MUTATION If the order of bases changes Amino Acid Sequence changes Proteins function changes Changes Phenotype a. Substitution or Point Mutation – change in a single base pair b. Frameshift Mutation – addition or deletion of a single base pair