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Replication, Transcription and Translation

Replication, Transcription and Translation. Honors Biology Powerpoint #2 – Chapter 12. Warm Up: Base Pairing. 1. A C C T G A. 2. G C T A. G A G. What is the DNA ‘backbone’ made of?. Phosphate and Sugar. Nucleotide. Hydrogen bonds.

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Replication, Transcription and Translation

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  1. Replication, Transcription and Translation Honors Biology Powerpoint #2 – Chapter 12

  2. Warm Up: Base Pairing 1. A C C T G A 2. G C T A G A G

  3. What is the DNA ‘backbone’ made of? • Phosphate and Sugar

  4. Nucleotide Hydrogen bonds Sugar-phosphate backbone Key Adenine (A) Thymine (T) Cytosine (C) Guanine (G) DNA Replication

  5. What is DNA replication? Why is DNA replication important for cells and multicellular organisms? Replication allows cells to divide Forming cells that are genetically identical to the original Making a copy of DNA

  6. When does DNA Replication occur? After the cell grows big enough to divide, during interphase, the “S” phase

  7. Original strand DNA polymerase New strand Growth DNA polymerase Growth Replication fork Replication fork Nitrogenous bases New strand Original strand DNA Replication

  8. Important Enzyme #1 Helicase • Unwinds DNA at the replication fork.

  9. Important Enzyme #2 DNA Polymerase • Principal enzyme in DNA replication; adds nucleotides to growing strand of DNA and proofreads new strand of DNA

  10. Steps in DNA Replication 1. Helicase enzyme breaks the hydrogen bonds between base pairs. This unzips the double helix at a position called the replication fork. 2. There is an abundant supply of nucleotides in the nucleus for the formation of the new polynucleotides. 3. Nucleotides base pair to the bases in the original strands with hydrogen bonds. 4. DNA polymerase joins together the nucleotides together with strong covalent bonds to form a new complementary polynucleotide strand. 5. The double strand reforms a double helix. 6. Two copies of the DNA molecule form behind the replication fork. These are the new daughter chromosomes.

  11. Drawings of the steps in DNA Replication DNA Polymerase Helicase

  12. Some Important DNA Facts • A strand of DNA has 2 ends, the 5’ (5-prime) and 3’ (3-prime) ends. • DNA is ALWAYS copied from 5’ to 3’

  13. Some Important DNA Facts • There are multiple ‘bubbles’ of DNA replicated at the same time

  14. What is ‘semi-conservative’ replication? Why is ‘semi-conservative’ important? • The DNA is copied EXACTLY generation to generation • In the new DNA created, one strand is from the original, and one is a new one. Semi = part of Conserve = save

  15. RNA • Where is DNA stored? ______________________ • What organelle makes proteins? ______________________ • Where are proteins made? ______________________ Nucleus Ribosomes Cytoplasm

  16. What problem might this pose? • DNA can not take directions for making proteins to the ribosomes.

  17. How does RNA solve this problem? • RNA is a disposable copy of DNA that can leave the nucleus

  18. B. RNA’s structure is very similar to the structure of DNA except for 3 major differences: • RNA has ribose sugar instead of deoxyribose Nitrogen Base

  19. 2. RNA is single-stranded 3. RNA has uracil (U) instead of thymine (T) DNA: AGTCCTTTAGT RNA: AGUCCUUUAGU

  20. There are three main types of RNA:

  21. 1. Ribosomal RNA (rRNA) rRNA is found in ribosomes, and creates the active site for protein formation

  22. 2. Transfer RNA(tRNA) tRNA contains the anticodon, and brings amino acids to create proteins

  23. 3. Messenger RNA (mRNA) mRNA provides the template for making proteins

  24. Adenine (DNA and RNA) Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only) RNApolymerase DNA RNA III. Transcription • Transcription: Producing RNA by copying part of the DNA’s nucleotide sequence

  25. RNA Polymerase rips open the DNA double helix • Describe the process of transcription using drawings. • RNA polymerase grabs bases and lines them up with the original DNA strand • Half of the DNA is copied into a strand of mRNA, then the DNA strand closes, hydrogen bonds reform

  26. Transcription

  27. How does RNA polymerase know where to start? Starts when it finds a “promoter” (specific base sequence) Found near the beginning of a gene sequence

  28. Describe the process of RNA editing • RNA editing is a process that occurs in the nucleus. • It removes introns “intervening sequences” and leaves mRNA with only the exons “expressed sequences.” • After editing a cap and tail are attached and the mRNA is ready to enter into the cytoplasm.

  29. IV. Translation • Proteins are long chains of amino acids. • Codon: 3 consecutive nucleotides that “code” for a specific amino acid. • What is the universal “start” codon: • AUG • What are the three “stop” codons? • UGA, UAA, UAG

  30. The Genetic Code

  31. The Genetic Code

  32. Use the genetic code below to translate the following mRNA sequences: • mRNA: A U G U A U C G GG C A U UUU A A • mRNA: U C C A U G G A A G U G A U U C C A U A A • mRNA: C C A U G U G U C CCC A A U G A AAA

  33. Use the genetic code below to translate the following mRNA sequences: • mRNA: A U GU A UC G GG C AU UUU A A • mRNA: U C CA U GG A AG U GA U UC C AU A A • mRNA: C CA U GU G UC CCC A AU G AAAA Methionine (START),Tyrosine, Arginine, Alanine, Phenylaline, STOP. Serine, Methionine, Glutamic Acid, Valine, Isoleucine, Proline, STOP Methionine, Cysteine, Proline, Glutamine, STOP, Lysine

  34. Translation: The decoding of RNA into a polypeptide chain (protein)

  35. The Central Dogma of Biology is: DNA  RNA  protein Where does the first step take place? Nucleus Where does the second step take place? Cytoplasm

  36. F. What is the job of tRNA during translation? Bringing amino acids to the ribosomes and match them up with the correct base on mRNA. What is an anticodon? The three bases on a tRNA that match with the mRNA codons. G. What is the role of the ribosome during translation? It is the site of protein assembly

  37. H. 1) mRNA is transcribed in the nucleus then travels to the cytoplasm Cytoplasm Nucleus mRNA

  38. Lysine (amino acid) Phenylalanine tRNA Methionine Ribosome Start codon mRNA 2) Ribosome grabs mRNA. tRNA brings amino acids to the ribosome Cytoplasm

  39. 3) tRNA matches with complimentary mRNA.Ribosome makes peptide bond between amino acids, and breaks the bond between tRNA and amino acid. Lysine Peptide bond tRNA Translation direction mRNA Ribosome

  40. Growing polypeptide chain Ribosome tRNA mRNA 4) Peptide chain continues to grow until ribosome reaches a stop codonProtein is complete. Stop codon

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