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DNA

DNA. Replication, Transcription & Translation REVIEW. DNA-the coolest molecule ever. DNA is a long molecule of nucleotides Components of Nucleotides 5-carbon sugar (deoxyribose) A phosphate group Nitrogenous base. Nitrogenous Bases. 4 kinds of Bases Adenine Guanine

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DNA

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  1. DNA Replication, Transcription & Translation REVIEW

  2. DNA-the coolest molecule ever • DNA is a long molecule of nucleotides Components of Nucleotides • 5-carbon sugar (deoxyribose) • A phosphate group • Nitrogenous base

  3. Nitrogenous Bases • 4 kinds of Bases Adenine Guanine Cytosine Thymine Purines=2 rings Pyrimidines=1 ring

  4. 5-Carbon Sugar and Phosphate • Make up the backbone of the DNA structure

  5. Chargaff’s Rule • American biochemist Erwin Chargaff • Noticed that the number of Adenine was almost always the same as Thymine in every organism. • Same for Guanine and Cytosine

  6. THE DOUBLE HELIX • **James Watson and Frances Crick developed the double helix model in which two strands were wound around each other**

  7. MORE DOUBLE HELIX • Looks like a twisted ladder • Hydrogen bonds exist between the nitrogenous bases in the center of the Helix • Certain bases only pair with other bases. • Use Chargaff’s rule to figure out which ones go together • Guanine -- Cytosine Thymine -- Adenine

  8. Nucleotide Hydrogen bonds Sugar-phosphate backbone

  9. Chromosomes • The nucleus of a human cell contains more than 1 meter of DNA • Chromosomes contain protein and DNA tightly packed: called chromatin • Proteins are called histones, DNA tightly curls around these proteins

  10. Replication/Duplication • DNA’s hydrogen bonds break down • Separation into two strands • Follows base pair rules to build two complementary strands • Now you have two identical DNA molecules

  11. How replication Occurs • Certain enzymes carry out Replication • DNA polymerase (enzyme) • Joins the complementary bases to the template • Works as a “proofreader” to make sure there are no mistakes in the Sequencing

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

  13. DNA Replication Animation • http://www.dnatube.com/video/335/Animated-DNA-Replication

  14. RNA • Disposable copy of a segment of DNA

  15. ? DNA vs. RNA Sugar # of strands Nucleotides

  16. Types of RNA • Messenger RNA: carries copies of instructions out of the nucleus (mRNA) • Ribosomal RNA: makes up the major part of RNA (rRNA) • Transfer RNA: transfers amino acids to the ribosome as specified by certain mRNA (tRNA)

  17. Transcription • Occurs in the nucleus • RNA molecules are produced by copying part of the nucleotide sequence of DNA into a complementary sequence of RNA. • Requires RNA polymerase

  18. Transcription cont. ? • **RNA polymerase binds to and separates DNA strands. RNA polymerase then uses one strand of DNA as a template for a complementary RNA strand**

  19. Promoters • RNA polymerase uses promoters to know where to start and stop • The promoters are specific sequences in the DNA that signal to RNA where to bind.

  20. Genetic Code • Goal: to make proteins to make polypeptides • Uses the 4 nitrogenous bases to form Codons. • Codon = three letter sequence that specify a single amino acid to be added to the polypeptide.

  21. UAGCACGGU would actually read: UAG CAC GGU

  22. UAGCACGGU would actually read • UAG CAC GGU serine Histidine Glycine 4 x 4 x 4 = 64 total three base codons

  23. What is… AUG UAA GCU CCC ?

  24. mRNA Codon Chart

  25. What is… CCG UAC GUA UUU ? mRNA Codon Chart

  26. Translation • Occurs in the cytoplasm • Uses codons from the mRNA to make proteins. • tRNA has anticodon and amino acids • Happens in the cytoplasm at a ribosome

  27. Think of it as a Secret Family recipe • The recipe is safe in your Mom’s kitchen • Recipe = DNA in nucleus • The copy is brought to others houses to make the food but the original stay in Mom’s kitchen • Copy = transcription • Others houses = ribosome • Food = proteins

  28. REVIEW http://www.bozemanscience.com/transcription-translation/ 12 min.

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