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Talk to a partner: DNA Recap

Talk to a partner: DNA Recap. RNA = Ribonucleic Acid Single stranded Contains the sugar RIBOSE instead of deoxyribose Contains the nitrogen base URACIL instead of thymine.

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Talk to a partner: DNA Recap

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  1. Talk to a partner: DNA Recap

  2. RNA = Ribonucleic Acid • Single stranded • Contains the sugar RIBOSE instead of deoxyribose • Contains the nitrogen base URACIL instead of thymine

  3. Messenger RNA (mRNA) copies instructions (nitrogen base sequence) from DNA in the nucleus and delivers them to the ribosome. 3 Types of RNA

  4. 2. Ribosomal RNA (rRNA) makes up the structure of the ribosome (remember ribosomes aren’t membrane-bound like other organelles!)

  5. 3. Transfer RNA (tRNA) delivers the necessary amino acids to the ribosome for protein assembly.

  6. Talk to a partner: Explain the function of the 3 types of RNA

  7. G1: Normal Cell Function

  8. Protein Synthesis

  9. RNA Recap

  10. RNA Recap • Single- stranded • Ribose sugar • Uracil replaces thymine • Can leave nucleus with DNA’s instructions • 3 types ~ mRNA, rRNA, tRNA

  11. Protein synthesis occurs in two steps: • Transcription • Translation

  12. Protein Synthesis

  13. Transcription • Process of copying a portion of DNA (gene), producing a complimentary strand of RNA • Think of RNA as a temporary copy of DNA that is used and then destroyed • RNA acts like an intermediate link between DNA in the nucleus and protein synthesis in the cytoplasm

  14. Steps of Transcription • 1. RNA polymerase (enzyme) attaches to part of DNA strand, separating a section of the DNA strand. (not the entire strand)

  15. Steps of Transcription 2. RNA polymerase uses one DNA strand as a template to assemble nucleotides into a complementary strand of mRNA. • This follows the base pairing rules for DNA replication except that in RNA, uracil rather than thymine, pairs with adenine.

  16. Steps of Transcription continued • mRNA separates from the DNA strand & leaves the nucleus. DNA strands rejoin/zip closed.

  17. Talk to a Partner Explain the process of transcription

  18. Transcription Animation

  19. Translation RNA to PROTEIN

  20. Translation into a Protein • Proteins are made by joining amino acids with a peptide bond into long chains called polypeptides. • Each polypeptide contains acombination of any or allof the 20 different amino acids. • The properties of proteins are determined by the number, order, and arrangement of amino acids joined together.

  21. The genetic code is read three letters at a time, so that each “word” of the coded message is three mRNA bases long. • This 3-letter “word” is known as a codon. • Each codon corresponds to a particular amino acid (the anti-codon on tRNA).

  22. Translation Animation

  23. Steps to Translation

  24. mRNA leaves the nucleus and attaches to a ribosome 2. The tRNA molecule with the correct anticodon attaches to the mRNA codon.

  25. 3.The AA is released from the tRNA. Peptide bond is formed between AA. 4.The mRNA slides through the ribosome.The next tRNA attaches to the mRNA codon. 5. This process continues until a STOP codon is reached.

  26. Talk to a Partner Translation: RNA to PROTEIN

  27. Protein Synthesis in Prokaryotes • Replication, transcription & translation occur in the cytoplasm at the same time

  28. Protein Synthesis in Eukaryotes • Replication, transcription & translation are separated by time and location

  29. Because there are 4 different bases, there are 64 possible 3-base codons. • 61 of them code for amino acids and 3 of them are “stop codons” that signal the end of the protein. • There is also one codon that can specify methionine or serve as the “start” codon for protein synthesis.

  30. Decoding codons into amino acids

  31. AUG ACC GGA AGC UGA UAC UGG CCU UCG ACU DNA: TAC TGG CCT TCG ACT mRNA: tRNA: Amino Acids: Met—Thr—Gly—Ser—(stop)

  32. Important Note • The genetic code is the SAME for every living organism, which means the codons represent the same amino acids in ALL living organisms.

  33. To sum it all up:

  34. RNA editing • Pre-mRNA transcribed in nucleus – not all bases will be translated into a protein • Exons – DNA bases that are transcribed into mRNA and eventually code for amino acids in proteins (=expressed genes) • Introns – DNA bases that are found btwn exons & are not translated into a protein (=interrupted genes)

  35. RNA editing continued • Exons are spliced together by enzymes to create mature mRNA that will become a protein Animation – no sound google chrome http://www.dnalc.org/resources/animations/

  36. Cornell Summary

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