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Biology - Chp 12 - DNA & RNA - PowerPoint

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  • 1. Chapter 12 DNA & RNA
  • 2. 12 – 1 DNA Deoxyribonucleic acid
  • 3.
    • In the middle of the 1900’s biologists were wondering how genes work. What they are made of, and how they determine the characteristics of organism
    • If the structures that carry genetic information could be identified, it might be possible to understand how genes control the inherited characteristics of living things
  • 4. How does DNA do the following things?
    • Carry info from one generation to the next
    • Put info to work by determining the inheritable characteristics
    • Copies itself, every time a cell divides
  • 5. Nucleotides
    • Units that make up DNA molecule
    • Made of three parts
    • 5 carbon sugar (deoxyribose)
    • Phosphate group
    • Nitrogen bases
  • 6. 4 kinds of nitrogen bases
    • Adenine (A)
    • Guanine (G)
    • Cytosine (C)
    • Thymine (T)
  • 7. Chargaff’s Rule
    • A=T and G=C
  • 8. X-Ray Evidence
    • Rosalind Franklin
    • British Scientist
    • Used a technique called X-Ray diffraction
    • Provided important clues about the structure of DNA
  • 9. X-Ray Evidence
    • There were 2 strands
    • Strands were twisted around each other (helix)
    • The nitrogen bases are in the middle
  • 10. Watson & Crick
  • 11. The Double Helix
    • Francis Crick & James Watson
    • Trying to understand the structure of DNA by building models
    • Unsuccessful until early 1953, Watson was shown a copy of Franklin’s X-ray pattern
    • “ The instant I saw the picture my mouth fell open and my pulse began to race.”
      • James Watson
    • Within weeks Watson and Crick had figured out the structure of DNA
    • Published their results in a historic one page paper in April of 1953
  • 12.  
  • 13.
    • Watson and Crick later discovered what held the two strands together
    • Hydrogen bonds could form between certain nitrogen bases and provide enough force to hold the two strands together
    • Hydrogen bonds could only form between certain base pairs adenine and thymine and guanine and cytosine
    • This principal is called Base pairing
    • This explains Chargaff’s Rule
  • 14.  
  • 15. 12 – 2 Chromosomes and DNA Replication
  • 16.
    • To extract DNA for analysis, you need to know where to find it and how its organized
    • DNA is located in the nucleus
    • DNA is organized into chromosomes
  • 17. Prokaryotic Cells
    • Prokaryotic cells have a single circular DNA molecule that contains nearly all of its genetic information
    • Located in the cytoplasm
  • 18. Eukaryotic Cells
    • Much more complex
    • 1000 times the amount of DNA as prokaryotes
    • DNA is located in the nucleus in the form of chromosomes
  • 19. Chromosome Structure
    • Q: If eukaryotic DNA can contain a meter or more of DNA, how does it get packed in so tight into chromosomes?
    • A: Eukaryotic chromosomes contain both DNA and protein that form a substance called chromatin
  • 20. Histones
    • Proteins that coil up DNA
    • DNA + histone molecules form a bead-like structure called a nucleosome
    • Nucleosomes pack together to form thick fibers that loop and coil together to form chromosomes
  • 21.  
  • 22. DNA Replication
    • When Watson and Crick discovered the double helix structure of DNA they recognized immediately how DNA could copy itself
    • The strands are complementary
    • If you could separate the two strands, the rules of base pairing would allow you to reconstruct the base sequence of the other strand
  • 23. Replication
    • When the DNA splits into 2 strands, then produces 2 new strands following the rules of base pairing
  • 24. How Replication Occurs
    • Replication is carried out by enzymes
    • Before DNA replicates, the double helix must unwind and unzip
    • There are many regulatory molecules used in replication
  • 25. DNA polymerase
    • Joins individual nucleotides to produce a DNA molecule, which is a polymer
    • Also proof reads each new DNA strand
  • 26. The Steps of Replication
    • DNA unwinds
    • DNA unzips
    • The bases attach from a supply in the cytoplasm
    • Sugar and phosphate groups form the side of each new strand
  • 27.  
  • 28.  
  • 29. Do Now Place the following steps of Replication in order. DNA unwinds DNA Unzips The bases attach from a supply in the cytoplasm Sugar and phosphate groups form the side of each new strand
  • 30. Do Now Place the following steps of Replication in order. DNA unwinds DNA Unzips The bases attach from a supply in the cytoplasm Sugar and phosphate groups form the side of each new strand 1. 2. 3. 4.
    • DNA replication results in 2 DNA molecules
    • Each with two new strands
    • One with two new strands and the other with two original strands
    • Each with one new strand and one original strand
    • Each with two original strands
  • 31. 12 – 3 RNA and Protein Synthesis
  • 32. Genes
    • Coded DNA instructions that control the production of proteins
  • 33.
    • DNA never leaves the nucleus, therefore the code must be copied into
    • RNA, or ribonucleic acid
    • There are 3 main differences between RNA and DNA
    • It has the sugar ribose, instead of deoxyribose
    • RNA is single stranded
    • RNA contains uracil in place of thymine
  • 34.
    • RNA is like a disposable copy of a segment of DNA
    • RNA is like a working copy of a single gene
  • 35. Types of RNA
    • Messanger RNA (mRNA)
    • Serve as messangers from DNA to the rest of the cell
    • 2. Ribosomal RNA (rRNA)
    • Type of RNA that makes up parts of ribosomes
    • 3. Transfer RNA (tRNA)
    • Transfers each amino acid to the ribosome as it is specified by the mRNA
  • 36. Types of RNA
  • 37. Transcription
    • RNA molecules are produced by copying part of the DNA sequence into RNA
    • Transcription requires an enzyme known as RNA polymerase
    • During transcription, RNA polymerase binds to DNA and separates the DNA strands. RNA polymerase then uses one strand of DNA as a template from which nucleotides are assembled into a strand of RNA.
  • 38.
    • Q: How does RNA polymerase “know” where to start and stop making a RNA copy of DNA?
    • A: promoters
    • Signals in DNA that indicate to the enzyme where to bind to make RNA
    • Similar signals in DNA cause transcription to stop
  • 39.  
  • 40.  
  • 41. RNA Editing
    • Remember, a lot of DNA doesn’t code for proteins
    • Introns – not involved in coding for proteins
    • Exons – code for proteins
  • 42.
    • The introns get cut out of the RNA molecules before the final mRNA is made
  • 43. The Genetic Code
    • Proteins are made by joining amino acids into long chains called polypeptides
    • Each polypeptide contains a combination of any or all of the 20 different amino acids
    • The properties of proteins are determined by the order in which different amino acids are joined together
    • The language of mRNA instructions is called the genetic code
  • 44.
    • The code is read three letters at a time
    • Each 3 letter “word” is called a codon
    • Each codon corresponds to an amino acid that can be added to the polypeptide
  • 45.  
  • 46. Serine-Histidine-Glycine UCG-CAC-GGU The codons represent the different amino acids: UCG-CAC-GGU This sequence would be read three bases at a time as: UCGCACGGU
  • 47. Translation
    • The sequence of nucleotide bases in an mRNA molecule serves as instructions for the order in which amino acids are joined to make a protein
    • Proteins are put together on ribosomes
  • 48. Translation
    • Decoding mRNA into a protein
  • 49. Steps of Translation
    • mRNA is transcribed from DNA in the nucleus and released into the cytoplasm
    • mRNA attaches to a ribosome
    • 3. as each codon of the mRNA molecule moves through the ribosome, the proper amino acid is transferred to the growing amino acid chain by tRNA
    • tRNA carries only one kind of amino acid and three unpaired bases called the anticodon
  • 50.
    • 4. The amino acid chain continues to grow until the ribosome reaches a stop codon on the mRNA molecule
  • 51.  
  • 52. The Roles of RNA and DNA
    • You can compare the different roles played by DNA and RNA molecules in directing protein synthesis to the two types of plans used by builders. A master plan has all the information needed to construct a building. But builders never bring the valuable master plan to the building site, where it might be damaged or lost. Instead, they prepare inexpensive, disposable copies of the master plan called blueprints. The master plan is safely stored in an office, and the blueprints are taken to the job site. Similarly, the cell uses the vital DNA “master plan” to prepare RNA “blueprints.” The DNA molecule remains in the safety of the nucleus, while RNA molecules go to the protein-building sites in the cytoplasm—the ribosomes
  • 53. Genes and Proteins
    • Q: If most genes contain nothing more than instructions for assembling proteins, what do proteins have to do with traits?
    • A: Everything, proteins are microscopic tools designed to build or operate a component of a living cell
  • 54. 12 – 4 Mutations
  • 55. Mutations
    • Changes in the genetic material
  • 56. Point mutations
    • Changes in one or a few nucleotides
    • Ex.) substitutions, insertions, deletions
  • 57.  
  • 58.  
  • 59.  
  • 60. Frameshift mutations
    • Mutation that shifts the “reading” frame of the genetic message by inserting or deleting a nucleotide
  • 61. Chromosomal Mutations
  • 62.  
  • 63.  
  • 64.  
  • 65. Significance of Mutations
    • Most mutations don’t do anything
    • Mutations that cause drastic changes in proteins produce defective proteins that disrupt normal biological activities
    • Mutations are also a source of genetic variability which can be beneficial
  • 66. Polyploidy
    • When plants produce triploid (3N) or tetraploid (4N) organisms
    • These plants are often larger and stronger
  • 67.  
  • 68. Do Now
    • Look at the bottom strand of DNA on the window blinds
    • Suppose the second T was changed to a C
    • How would this specifically alter the resulting amino acid chain?
    • What kind of mutation is this?
  • 69. Do Now #2
    • What if we got rid of the first G in the bottom strand of DNA
    • How would this specifically alter the amino acid chain produced?
    • What kind of mutation is this?
  • 70. Do Now #3
    • How are substitution/point mutations and frameshift mutations similar?
    • How are they different?

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