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Molecular Genetics: DNA and RNA - The Genetic Materials

This unit explores the history and structure of DNA as the genetic material, including topics such as DNA replication, transcription, translation, and the genetic code. It also covers the role of RNA in carrying DNA's instructions and the process of protein synthesis.

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Molecular Genetics: DNA and RNA - The Genetic Materials

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  1. Unit 6 Molecular Genetics

  2. DNA and RNA I. DNA- deoxyribonucleic acid A. History of DNA as Genetic Material “code of life” 1. Griffith and Transformation a. Frederick Griffith made discovery while investigating bacteria known to produce pneumonia b. Griffith isolated two different strains of bacteria

  3. Molecular Genetics DNA: The Genetic Material DNA Structure • Nucleotides • Consist of a • five-carbon sugar • a phosphate group • a nitrogenous base

  4. Base Groupings Purines (Double ringed) • Adenine • Guanine Pyrimidines (Single ringed) • Cytosine • Thymine

  5. Backbone of DNA chain formed by sugar and phosphate groups of nucleotides sugar phosphate

  6. Chargaff’s Rule- ratio of guanine:cytosine and adenine:thymine are equal A = T and G = C

  7. Molecular Genetics DNA: The Genetic Material X-ray Diffraction • 1950’s Rosalind Franklin used X-ray diffraction to study structure of DNA molecule. Concluded structure was coiled like a spring (helix) • X-ray diffraction data helped solve the structure of DNA

  8. X-ray Diffraction cont’d… • Indicated that DNA was a double helix

  9. Molecular Genetics DNA: The Genetic Material Watson and Crick • After looking at Franklin and Wilkin’s work, Watson and Crick constructed a model of DNA molecule (1953)

  10. Molecular Genetics DNA: The Genetic Material DNA Structure • DNA often is compared to a twisted ladder. • Rails of the ladder are represented by the alternating deoxyribose and phosphate. • The pairs of bases (cytosine–guanine or thymine–adenine) form the steps.

  11. START HERE • https://www.youtube.com/watch?v=oefAI2x2CQM • Amoeba Sis-Transcription-Translation

  12. DNA: The Genetic Material Chromosome Structure • DNA coils around histones to form nucleosomes, which coil to form chromatin fibers.

  13. Quick Molecular Genetic Terminology • Replication= DNA DNA • Transcription= DNA RNA • Translation= RNA Amino Acids • Polypeptide= Chain of amino acids • Adenine, cytosine, & guanine= DNA & RNA • Thymine= DNA Only • Uracil= RNA Only

  14. RNA carries DNA’s instructions. • information flows in one direction from DNA to RNA to proteins.

  15. replication transcription translation • includes three processes. • Replication • Transcription • Translation • RNA is a link between DNA and proteins.

  16. Molecular Genetics Replication of DNA Replication • Parental strands of DNA separate, serve as templates, and produce DNA molecules that have one strand of parental DNA and one strand of new DNA

  17. Molecular Genetics Replication of DNA Unwinding • DNA helicase, an enzyme, is responsible for unwinding and unzipping the double helix. • RNA primase adds a short segment of RNA, called an RNA primer, on each DNA strand.

  18. Molecular Genetics Replication of DNA Joining • DNA polymerase removes the RNA primer and fills in the place with DNA nucleotides. • DNA ligase links the two sections.

  19. Molecular Genetics Replication of DNA Comparing DNA in Eukaryotes and Prokaryotes • Eukaryotic DNA located in cells nucleus in form of a number of chromosomes • In prokaryotes, the circular DNA strand is opened at one origin of replication.

  20. Molecular Genetics DNA makes RNA makes protein • RNA • Contains the sugar ribose and the base uracil • Usually is single stranded

  21. Molecular Genetics Transcription makes 3 Types of RNA Messenger RNA (mRNA) • complementary to one strand of DNA • Carries message that will be translated to form a protein Ribosomal RNA (rRNA) • Forms part of the ribosome where proteins are made Transfer RNA (tRNA) • Transports amino acids to the ribosome

  22. Molecular Genetics

  23. Molecular Genetics • DNA is unzipped in the nucleus and RNA polymerasebinds to a specific section where an mRNA will be synthesized. Transcription • DNA to mRNA Animation

  24. DNA RNA polymerase moves along the DNA • Nucleotides pair with one strand of the DNA. • RNA polymerase bonds nucleotides together. • The DNA helix winds up again

  25. RNA • The RNA strand detaches from the DNA once the gene is transcribed.

  26. Replication vs Transcription • Copies all DNA • Makes one copy of DNA • Copies a gene • Can make many copies of RNA

  27. codon for methionine (Met) codon for leucine (Leu) TRANSLATION Amino acids are coded by mRNA base sequences. • Translation converts mRNA messages into polypeptides. • A codon is a sequence of three nucleotides that codes for an amino acid.

  28. Molecular Genetics The Code • DNA code is a three-base code. • The three-base code in mRNA is called a codon.

  29. Molecular Genetics Translation • RNA Amino Acid • In translation, tRNA molecules act as the interpreters of the mRNA codon sequence. • Each anticodon (on tRNA) is complementary to a codon (on mRNA).

  30. Amino acids are linked to become a protein. • An anticodon is a set of three nucleotides that is complementary to an mRNA codon. • An anticodon is carried by a tRNA.

  31. Codons • 64 possible codons • 20 different amino acids

  32. Codons Start Codon • AUG Stop Codons • UGA • UAA • UAG

  33. Molecular Genetics

  34. https://www.youtube.com/watch?v=oefAI2x2CQM • Amoeba Sis-Transcription-Translation • https://www.youtube.com/watch?v=2BwWavExcFI Transcription and Translation Animation

  35. Extra Facts • Genes give instructions for making proteins • It is possible for more than one combo of codons to code for the same amino acid because there are 64 different types of codons, but only 20 amino acids • Takes 3 bases to code for 1 amino acid

  36. Molecular Genetics Chapter 12 12.3 DNA, RNA, and Protein RNA Processing • The code on the DNA is interrupted periodically by sequences that are not in the final mRNA. • Intervening sequences are called introns. • are cut out by enzymes • The portions of DNA molecules that actually code for the production of proteins are called exons. • parts of the mRNA that are kept and expressed

  37. Molecular Genetics Chapter 12 12.4 Gene Regulation and Mutation Mutations • A permanent change that occurs in a cell’s DNA • 2 Main Types of Mutations: • Gene • Chromosomal

  38. Molecular Genetics Chapter 12 12.4 Gene Regulation and Mutation Causes of Mutation • Can occur spontaneously • Radiation such as UV rays, X rays and gamma rays • Chemicals – Mutagens & carcinogens • Nondisjunction • Viral Infection- HPV

  39. Molecular Genetics Chapter 12 12.4 Gene Regulation and Mutation Body-cell v. Sex-cell Mutation • Somatic cell mutations are not passed on to the next generation. • Mutations that occur in sex cells are passed on to the organism’s offspring and will be present in every cell of the offspring.

  40. Gene mutations • Point mutations – mistakes with 1 nucleotide • Substitution of the wrong nucleotide (nitrogen base) in place of correct one • Frameshift mutations – occur when a nucleotide is either inserted or deleted, altering the codon sequence • More severe than point mutations because it affects all of the amino acids in the protein

  41. Chromosomal mutations • Change in the number or structure of the chromosomes • Duplication • Inversion • Translocation

  42. Molecular Genetics Chapter 12 12.4 Gene Regulation and Mutation

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