DNA (deoxyribonucleic acid)- a nucleic acid which stores genetic traits in the proteins it codes for. All living things contain DNA. DNA is a nucleic acid. Nucleic acids are made of nucleotide subunits hooked together.

Nucleotides- subunits of DNA made of: 1. Phosphate (PO 4 ) 2. Sugar (deoxyribose). 3. Nitrogen base. Nucleotides

Four different nitrogen bases makes four different nucleotides: –Guanine –Cytosine –Adenine –Thymine These four nucleotides make up the DNA of almost every single living thing. Nitrogen Bases

Nucleotides

Chargaff’s Rule He measured amounts of each base in various organisms and found: % of adenine (A) = % thymine (T) % of cytosine (C) = % guanine (G) Chargaff’s rule told us that A bonds to T and C bonds to G If 20% of strand is A, what %T? %C?

Structure of DNA Discovered by Watson and Crick Double helix- 2 spiral strands of nucleotides bonded together

Structure of DNA Siderail backbone is the sugar and phosphates of nucleotides Rungs are the nitrogen bases of nucleotides –A----T –C----G Hydrogen bonds between bases hold two strands together

What is DNA Replication? Replicate = make “exact” copies. DNA replication- copying of DNA so that a cell made divide All DNA must be replicated before a cell can divide. Why?

Enzymes and Replication Helicase- enzyme that unwinds DNA DNA polymerase-enzyme that moves along each strand and brings in bases for new strand copy

DNA Replication Can be a mistake in replication Mutations-change in DNA Mutagens- substances that cause mutations – X-rays –Toxins –Drugs –UV light, etc.

Mutations 3 types of mutations that can occur during DNA replication: –Insertions -extra nucleotides –Deletions –missing nucleotides –Substitutions –placement of wrong nucleotides Can be helpful or harmful mutations. Insertion Deletion Substitution

Most Destructive Mutation? The bases, A, C, G, and T can be equated to letters of a “DNA sentence” THE DOG WAS HOT IN THE SUN Substitution: THE DOG WAS NOT IN THE SUN Insertion? THE DOG NWA SHO TIN THE SUN Deletion? THE DOG ASH OTI NTH ESU N Why should I care?

How Much DNA Is In OUR Cells?  Chromosome-strands of DNA coiled tightly  Human cell has 46 (23 pairs)  23 from Mom  23 from Dad  Other organisms have different numbers of chromosomes

2 Types of Cells  Somatic cells –all body cells except sex cells  Diploid  chromosomes are in pairs  46=23 pairs for humans  1 set (23) from mom, 1 set (23) from dad  Gametes - sex cells  Egg & sperm  Haploid  no pairs (only 23 single chromosomes)

If all body cells contain the same # of chromosomes, why are all cells so different? Different cells make different proteins due to different “active” segments of DNA. –Heart cells make proteins needed for the heart to work properly –Brain cells make proteins needed for the brain to work properly

What is the Purpose of DNA? DNA stores the genetic information that codes for proteins. ALL CELL FACTORIES MAKE PROTEINS!

What is the Purpose of DNA? Gene- a segment of DNA that codes for a protein. DNA has 1000’s of genes to make many different types of proteins. Why are proteins important? Protein - polymer of amino acids aa—aa—aa—aa—aa—aa—aa—aa = protein

What is the Purpose of DNA?

RNA (Ribonucleic acid) Stores the genetic code in the nucleus Double stranded Sugar of DNA nucleotides = deoxyribose A, C, G, T “DNA is DNA” Found in nucleus only Transmits the genetic code to the rest of the cell Single stranded Sugar of RNA nucleotides is ribose A, C, G, U (uracil) NO T! Different forms: mRNA, rRNA, tRNA Found all over cell _____DNA____ vs._____RNA___

DNA vs. RNA

Part 1of Protein Synthesis: Transcription Transcription- copying of DNA to mRNA that occurs in the nucleus. DNA complementary to mRNA ATA-CGG-AAT(DNA) transcription in nucleus UAU-GCC-UUA (RNA)

Transcription Translation cytoplasm

Part 2 of Protein Synthesis: Translation: Translation- converting mRNA to protein which occurs at ribosomes in the cytoplasm mRNA codons translation by ribosomes a.a.---a.a---a.a (protein) cytoplasm

Part 2 of Protein Synthesis: Translation: Codon-three bases of mRNA that code for an amino acid UAU-GCC-UUA (3 mRNA codons) translation by ribosomes a.a.---a.a---a.a. (protein) mRNA needs the help of tRNA to bring in the amino acids to be hooked together cytoplasm

Whole Process ATA-CGG-AAT(DNA) transcription in nucleus UAU-GCC-UUA (3 mRNA codons) translation in cytoplasm at ribosomes a.a.-a.a-a.a. (protein) How do we know what amino acid results? The Codon Wheel!!!

Part #1 Transcription Part #2 Translation cytoplasm

The Codon Wheel ***How do we use the wheel? There are 2 clues.

The Codon Wheel

Whole Process DNA: ATA-CGG-AAT transcription in nucleus mRNA:UAU-GCC-UUA(3 codons) translation in cytoplasm protein: a.a.-a.a-a.a. tyrosine-alanine-leucine Protein Synthesis Animation! How do we know what amino acid results? The Codon Wheel!!!

Amino Acids Where do our cells get these amino acids to build the proteins? From FOOD! We eat proteins, then these proteins are broken down (metabolized) into amino acids in our stomach. We reuse these amino acids to build other proteins.