DNA Replication, Transcription, and Translation The Making of a Protein DNA Replication • Process by which DNA copies itself • Happens when chromosomes copy themselves before mitosis and meiosis Steps of DNA Replication: 1. DNA untwists 2. DNA unzips (separates) 3. Corresponding free- floating nucleotides attach to original sides to form new base pairs 4. DNA reforms Identical 5. 2 strands twist into helix Strand animation Complementary base pairing allows each strand of DNA to serve as a template for DNA replication SEMI-CONSERVATIVE REPLICATION DNA Replication – Something old and something new in the daughter molecules, known as semi- conservative replication (part of the original DNA is conserved) RNA - Ribonucleic Acid “DNA Messenger & Taxi” RNA Structure & Function From DNA to Protein What is RNA? Organic Molecule Nucleic Acid Three types mRNA = messenger tRNA = transfer rRNA = ribosomal (combines with proteins to form ribosomes) Where is RNA located? mRNA -in nucleus & cytoplasm rRNA tRNA - only in cytoplasm rRNA – found in mRNA ribosomes (cytoplasm) mRNA tRNA What is RNA’s structure? 1. Nucleotides= • Phosphate (Acid) a. Phosphoric Acid • Sugar-Base b. Ribose sugar • Phosphate (Acid) c. Nitrogenous Bases: • Sugar-Base Adenine-Uracil • Phosphate (Acid) Guanine-Cytocine • Sugar-Base 2. Single Strand • Phosphate (Acid) 3. No Twisted helix • Sugar-Base Comparison of RNA & DNA: • Acid Acid Acid • Uracil Sugar-Base -- Sugar- Thymine -Sugar • Acid Acid Acid • Sugar-Base Sugar- Base -Sugar • Acid Acid Acid • Sugar-Base • Acid Sugar- Base- Sugar Deoxy- ribose • Ribose Sugar-Base Acid Acid RNA DNA Ladder What are mRNA’s functions? mRNA= • Copies the DNA code • Goes out into the cytoplasm to tell the cell what to do in order to stay alive • Delivers message to ribosomes (protein factories) Why not send the original DNA code out? • DNA is the master Original DNA copy – must be protected • DNA might be damaged! DNA in the • DNA can’t fit through nucleus is nuclear pores safe • mRNA components are reused • To copy more messages mRNA -copy Transcription 1. mRNA is copied from DNA 2. Occurs in the nucleus 3. Steps: • DNA untwists • Unzip one gene in DNA • RNA codons line up to corresponding bases on one side of DNA • mRNA detaches from the DNA DNA: GAG • mRNA moves out of the AAC TAG nucleus and into the TAC cytoplasm RNA: CUC UUG AUC AUG RNA Review: mRNA has: mRNA • Single strand A • Ribose sugar U • Uracil instead T A of thymine C bases G • Nuclear G membrane C allows it to DNA Code leave! Transcription DNA mRNA mRNA Cytoplasm of cell Nucleus Transcription Then the mRNA Once in the happens in the that has been cytoplasm, the nucleus. An RNA made moves out of mRNA is used to copy of a gene is the nucleus into make a protein made. the cytoplasm How does mRNA tell the cell what to do? • mRNA is a message that codes for a protein • Proteins are made in the cytoplasm and work to keep the cell alive • Translation (protein synthesis): Process of making a protein • Proteins are made up of amino acids (small building blocks) Transcription Review QuickTime™ an d a decompressor are need ed to see this p icture . There are 20 different types of amino acids Protein Amino Acids Protein Synthesis Assembling Proteins from the DNA Instructions tRNA: Amino • in cytoplasm acid • Picks up an amino acid • “Taxis” the amino acid to the tRNA ribosome protein factories Translation • Conversion of the message (mRNA code) into a protein by the ribosome factories Nucleus Translation Cytoplasm 1. mRNA moves out of nucleus and into cytoplasm 2. mRNA attaches to a ribosome 3. Transfer RNA (tRNA) decodes the Ribosome mRNA and brings amino acids to build up the protein tRNA Amino acid Anticodon (3 bases on tRNA): Matches up to codons on mRNA 4. Protein (chain of amino acids) detaches from ribosome and goes off to work in the cell 4. Polypeptide Chain of amino acids grows 2. Peptide 1. tRNA bond forms delivers 3. tRNA leaves amino acid ribosome Putting It All Together Genetic Code Code that matches codons in mRNA to amino acids on tRNAs mRNA codons (3 bases) Amino Stop codon – codes for acids the end of the mRNA (no amino acid added) Different codons code for different amino acids!!! Summary: DNA Replication: Protein Synthesis: Transcription: • Make duplicate - make mRNA from DNA DNA (in nucleus, moves out • In nucleus into cytoplasm) • Copy the Translation: chromosomes - make protein from mRNA code using • Occurs before amino acids (on mitosis and ribosome in cytoplasm) meiosis Translation Review QuickTime™ an d a decompressor are need ed to see this p icture .
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