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Protein Synthesis
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What? Where? When? DNA RNA Protein
WHAT: Protein synthesis is the process of making proteins from the DNA code. There are two steps: Transcription & Translation. DNA RNA Protein WHERE: Transcription: Nucleus Translation: Cytoplasm WHEN: Whenever a protein is needed somewhere in the body. Ex: Enzymes, Hormones, Pigments
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Gene Expression Expressed = turned into a protein.
The phenotype is determined by the genes expressed.
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2 Steps to Protein Synthesis:
1. Transcription 2. Translation
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Transcription DNA RNA
RNA Polymerase (enzyme) adds RNA nucleotides to create messenger RNA (mRNA). mRNA carries the copied DNA code from nucleus to cytoplasm. Occurs in the nucleus.
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Messenger RNA
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REMINDER: RNA nitrogenous bases: A, U, G, C A bonds with U
G bonds with C Ribose Sugar
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DNA vs. RNA DNA RNA Sugar = deoxyribose Sugar = ribose
Double-stranded molecule Single-stranded molecule Thymine bonds with adenine Uracil instead of thymine
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Translation mRNA protein
The ribosome reads the copied mRNA code and attaches amino acids together to make a protein. Amino acids are connected together by peptide bonds. Occurs in the cytoplasm.
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How does the ribosome read mRNA?
The ribosome reads the mRNA code in codons. Codon: 3 nitrogenous RNA bases in a row. Each codon codes for 1 amino acid. Ex: AUG = Methionine
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Where are the amino acids?
Transfer RNA (tRNA) molecules carry the amino acid to the ribosome. Each tRNA has an anticodon that complements the mRNA codon. Ex: mRNA codon: AUG tRNA anticodon: UAC -AUG codes for Methionine -The tRNA with antiocodon UAC carries amino acid Methionine
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Summary:
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What is the difference between DNA Replication & Protein Synthesis?
DNA Replication: DNA DNA *********************************** Transcription: DNA mRNA Translation: mRNA Protein
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How can we avoid mutations (errors)?
Code has duplicates Sometimes a small error does not ruin the protein being made. Start Codon: AUG Methionine Stop Codons: UAA, UGA, UAG
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KEY FACTS TO REMEMBER: DNA is the genetic material. DNA codes for protein (but it cannot leave the nucleus, so it creates a “messenger” (mRNA) to bring the code to the ribosome in the cytoplasm. The amino acid chart is based off of the mRNA codons (not tRNA anticodons).
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