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Protein Synthesis

Protein Synthesis. Protein Synthesis. DNA acts like an "instruction manual“ it provides all the information needed to function the actual work of translating the information into a medium that can be used directly by the cell is done by RNA RNA= Ribonucleic acid. RNA.

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Protein Synthesis

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  1. Protein Synthesis

  2. Protein Synthesis • DNA acts like an "instruction manual“ • it provides all the information needed to function • the actual work of translating the information into a medium that can be used directly by the cell is done by RNA • RNA= Ribonucleic acid

  3. RNA • Similar molecule to DNA • Made up of a long chain of nucleotides • 3 main differences between DNA and RNA • Single stranded • Sugar= ribose • Contains Uracil instead of Thymine

  4. Types of RNA (1) • mRNA- messenger RNA • carry instructions for making proteins • Made during transcription

  5. Types of RNA (2) • rRNA- ribosomal RNA • Along with proteins make up Ribosomes

  6. Types of RNA (3) • tRNA- transfer RNA • Bring amino acids to the ribosome to construct proteins

  7. Reading the DNA code • What is DNA used for? • To make proteins that control growth and repair in a living organism • Steps to making a protein (Protein Synthesis) • DNA RNA Protein • DNA RNA= Transcription - change writing • RNA Protein= Translation - change language

  8. RNA • RNA a disposable copy of a part of DNA • A working copy of a single gene • Main job used in Protein synthesis • Why can’t we just send DNA out into the cytoplasm ? • It could get damaged, information could be lost

  9. Transcription • Part of a DNA molecule is copied into a single strand of RNA (changing the writing) • Where does transcription take place? • the nucleus animation

  10. Key “players” • Transcription factors- • Proteins that bind to promoter regions of a gene • “show” RNA polymerase where to bind • RNA polymerase- • Binds to DNA • Separates the strands • Uses one strand of DNA as a template to make RNA

  11. animation

  12. Step 1 • Initiation- RNA polymerase binds to DNA promoter region • Promoter region- specific base sequence that RNA polymerase binds to • The promoter contains an initiation site where transcription of the gene begins.

  13. Step 2 • Elongation- nucleotides are bound together based on the DNA template • Assembles RNA strand based on template (3’  5’ strand)

  14. Step 2 • RNA polymerase arranges nucleotides that are complimentary to the DNA strand being copied. • RNA contains uracil instead of thymine. • A gene can be transcribed many times by multiple RNA polymerase molecules

  15. Step 3 • Termination- RNA polymerase stops transcription • RNA polymerase continues to elongate until it reaches the terminator • Termination= a specific sequence of nucleotides that signals the end of transcription.

  16. Transcription video • Transcription on hemoglobin

  17. RNA editing • Where on the DNA strand does transcription begin? • At the promoter • Extra DNA is transcribed into RNA • DNA contains nucleotides that are not involved in making proteins (introns) • Before RNA leaves the nucleus introns are cut out leaving just exons (sequences that code for proteins)

  18. Translation Protein synthesis

  19. Translation • mRNA leaves the nucleus and is used to create a protein needed by the cell • RNA Proteins • Change the language

  20. Proteins • Made of a long chain of amino acids called a polypeptide • 20 different amino acids in the human body • Your body makes about half of them, the other 10 come from your food • The code for making proteins is found on the mRNA strand

  21. Genetic Code • The mRNA strand is “read” 3 letters at a time • Each 3 letter sequence is called a codon • Some amino acids are made by more then 1 codon • START codon- indicates the start of the protein • STOP codon- ends translation, does not code of an amino acid

  22. Amino Acid Chart

  23. Translation • Takes place in the Ribosomes 4 steps • As the mRNA strand is read by the ribosome tRNA brings the correct amino acid • Each tRNA carries only 1 amino acid • tRNA has 3 unpaired bases (anticodon) that are complimentary to the mRNA strand

  24. Translation (cont.) • Amino acid is transferred to the growing polypeptide chain • Each ribosome has 2 binding sites

  25. Translation (cont.) • Ribosome adds a polypeptide bond between the amino acids

  26. Translation (cont.) 4. Translation continues until a STOP codon is reached • 3 STOP codons • UAA • UAG • UGA animation

  27. Practice

  28. Putting it all together • A short length of DNA is copied into mRNA • mRNA leaves the nucleus and enters the cytoplasm • A ribosome reads the strand of mRNA in sets of 3 and matches the tRNA with its amino acid • Amino acids are released from tRNA and bond together in order making a polypeptide • The polypeptide folds into a functional protein to be used by the organism.

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