DNA

What is DNA? A nucleic acid Carries genetic information on how to make proteins AKA the blueprint (instructions) Located in the nucleus of a cell

Overall Structure of DNA Shape is called a Double Helix-has two strands (Looks like a twisted ladder) The sides of the “ladder” are a phosphate-sugar backbone The rungs of the “ladder” are nucleotides

Nucleotide Parts A nucleotide from each strand connects to each other to form the rungs on the ladder Nucleotides are made of 3 parts: Phosphate Deoxyribose Sugar Base

Nucleotide Base-Pairing Rules Adenine-Thymine (A-T) Guanine-Cytosine (G-C)

DNA 2 meters of DNA in each cell of your body DNA wraps around histone proteins to form chromatin Before cell division, chromatin winds up (condenses) to form chromosomes

DNA Replication Process is called semi-conservative: Each “new” molecule of DNA has one strand that is new, and one that came from the original strand

Replication Process Helicase unwinds the DNA & separates the strands DNA polymerase binds to each template strand of DNA As DNA polymerase moves along the strand, new nucleotides are added RESULT: 2 identical DNA molecules

Protein Synthesis

DNA vs. RNA RNA Structure DNA Structure Single stranded Sugar = ribose Bases: Adenine Cytosine Guanine Uracil Double stranded Sugar = deoxyribose Bases: Adenine Cytosine Guanine Thymine

Base-Paring Rules in RNA

RNA Function-Make proteins! Messenger RNA (mRNA) Carries DNA message from nucleus to ribosome Ribosomal RNA (rRNA) Makes up part of the ribosome Transfer RNA (tRNA) Carries the correct amino acid to the ribosome

Transcription & Translation Two steps: Transcription: Process of copying a DNA message onto an mRNA molecule. Translation: Process of translating the message on an mRNA into a protein.

Transcription the production of an mRNA copy of a gene for use in protein synthesis this process allows the cell to keep the DNA master copy safe within the nucleus uses RNA polymerase to match up bases to make a copy of one gene that will code for a protein when complete, the mRNA copy detaches, leaves the nucleus, and attaches to a ribosome in the cytoplasm

Translation the process of turning the code contained in DNA into a sequence of amino acids – occurs at ribosomes every 3 bases on the mRNA equals one codon each codon codes for a specific amino acid each codon on the mRNA matches up to an anticodon on a tRNA (which carries the correct amino acid) this translation of the codons in mRNA into a sequence of amino acids is how proteins are made, and how genes are expressed

Central dogma DNA Transcription mRNA Translation Protein

Detailed Steps: Transcription 1. the DNA unwinds at the gene that needs to be copied 2. RNA polymerase matches up RNA nucleotides to the exposed gene sequence on the DNA 3. As RNA polymerase matches the nucleotides, they join together to form a strand of mRNA 4. Once the gene is copied, the mRNA disconnects from the DNA and is edited before leaving the nucleus.

Detailed Steps: Translation 1. the mRNA binds to a ribosome at the start codon (AUG) 2. the tRNA with the correct anti-codon (UAC) and the amino acid Methionine (Met) joins to the start codon 3. the tRNA with the correct anticodon binds to the next codon 4. a peptide bond forms between Methionine and the amino acid attached to the second tRNA 5. as each tRNA binds to the mRNA, the amino acids are joined into a peptide chain 6. when complete, the peptide chain is modified and folded to become a functional protein 7. each tRNA reloads with the correct amino acid to be ready for the round of protein synthesis

Codons & Anti-Codons Every 3 nucleotides makes up a codon, and each codon matches up with an anti-codon on a tRNA molecule that has a specific amino acid attached to the other end

Protein synthesis Example: DNA: TAC CGG TAA CGC mRNA: AUG GCC AUU GCG Amino Acid: Met Ala Ile Ala