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DNA Transcription and Translation

Explore the fascinating world of DNA transcription and translation, from the major job of DNA to protein assembly. Learn about the differences between DNA and RNA, the steps of transcription and translation, and the essential role of gene expression in cellular biology.

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DNA Transcription and Translation

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  1. Do Now:Imagine you have an original Michaelangelo painting. What would you do with it? How would you prevent it from getting damaged? Why are we talking about paintings at all???

  2. DNA Transcription and Translation

  3. What is the major job of DNA? How does it do that job? • Form proteins • Store instructions in DNA • Copy instructions tomore DNA or RNA • Transmit by translating instructions to amino acid (aa) chain

  4. Do DNA and RNA look the same? RNA • Several types • Single stranded • Ribose Sugar • A, C, G, U • Can leave nucleus DNA • Double stranded • Deoxyribose Sugar • A, C, G, T • Isolated in nucleus

  5. ~ 3 Types of RNA ~ • mRNA (messenger) – carry DNA info to cytoplasm • rRNA (ribosomal) – attach to mRNA, use info to assemble aa’s in correct order • tRNA (transfer) – transports aa’s to ribosome to assemble proteins

  6. How do we get from DNA to RNA??? • Process of getting info in DNA out of nucleus to cytoplasm • RNA copy made in nucleus • mRNA carries info Transcription!!!

  7. Steps of Transcription • Enzyme helicaseunzips DNA

  8. RNA polymerase pairs RNA nucleotides with complementary bases on DNA template strand (U’s instead of T’s)

  9. Completed mRNA strand breaks away • DNA rezips • Mature mRNA has a cap and tail (protects); all unused parts of message are edited out • mRNA leaves through nuclear pore • mRNA enters cytoplasm Who will mRNA meet?

  10. How do we now get to protein assembly??? TransLATION!!! Transcribe vs. Translate *Rewriting in *Converting one different form language into (language) another

  11. A little about protein language… • What are the building blocks of proteins? • AMINO ACIDS!! • Remember: 20 different amino acids • aa’s coded for by THREE nucleotides –codons • 4 bases, 3 per codon: 43 = 64 total possible combinations

  12. Why don’t these numbers match? 20 amino acids, 64 options?? WOBBLE In case of mistakes in DNA, close combinations can result in replacement of same amino acid

  13. Do all organisms have same code? Why or why not??? • ALL organisms share same code • Most codons code for amino acids • START codon (AUG) - Methionine • STOP codons (UGA, UAA, UAG) – end protein production

  14. Steps of Translation • Ribosomes (rRNA) attach to mRNA carries code  tRNA’s carry amino acid and have anticodon complementary to mRNA

  15. Protein production starts when START (AUG) is coded for

  16. Ribosome slides along mRNA in 3’s (in frame) and tRNA brings matching aa’s

  17. aa’s joined by dehydration synthesis to form peptide bond; tRNA released

  18. Process continues until STOP codon is reached

  19. Gene Expression ** Central idea of cellular and molecular biology ** DNA → RNA → amino acid → protein chain

  20. Interactive Gene Expression Activity

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