1 / 74

DNA : The Genetic Material

DNA : The Genetic Material. Chapter 9 By: Mrs. Fleck. Identifying the Genetic Material Section 1. Transformation - is a change in genotype caused when cells take up foreign genetic material. Griffith’s experiments discovered transformation.

karina-morrison
Télécharger la présentation

DNA : The Genetic Material

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. DNA : The Genetic Material Chapter 9 By: Mrs. Fleck

  2. Identifying the Genetic MaterialSection 1 • Transformation-is a change in genotype caused when cells take up foreign genetic material. • Griffith’s experiments discovered transformation. -caused harmless bacteria (even dead) to become deadly. Vaccine- is a substance that is prepared from killed or weakened disease causing agents. • Virulent-able to cause disease • Avery’s experiments- conclude -that DNA is the material responsible for transformation. • -Bacteriophage – is a virus that infects bacteria • Hershey –Chase Experiments- concluded DNA , rather than proteins , is the heredity material .

  3. Section 11.1 Summary – pages 281 - 287 DNA as the genetic material • Hershey and Chase labeled the virus DNA with a radioactive isotope and the virus protein with a different isotope. • By following the infection of bacterial cells by the labeled viruses, they demonstrated that DNA, rather than protein, entered the cells and caused the bacteria to produce new viruses.

  4. Section 11.1 Summary – pages 281 - 287 What is DNA? • All actions, such as eating, running, and even thinking, depend on proteins called enzymes. • Enzymes are critical for an organism’s function because they control the chemical reactions needed for life. • Within the structure of DNA is the information for life—the complete instructions for manufacturing all the proteins for an organism.

  5. Section 11.1 Summary – pages 281 - 287 The structure of nucleotides • DNA is a polymer made of repeating subunits called nucleotides. Nitrogenous base Phosphate group Sugar (deoxyribose) • Nucleotides have three parts: a simple sugar, a phosphate group, and a nitrogenous base.

  6. Section 11.1 Summary – pages 281 - 287 The structure of nucleotides • The simple sugar in DNA, called deoxyribose (dee ahk sih RI bos), gives DNA its name—deoxyribonucleic acid. • The phosphate group is composed of one atom of phosphorus surrounded by four oxygen atoms.

  7. Section 11.1 Summary – pages 281 - 287 The structure of nucleotides • A nitrogenous base is a carbon ring structure that contains one or more atoms of nitrogen. • In DNA, there are four possible nitrogenous bases: adenine (A), guanine (G) are (Purines)=double ring of carbon and nitrogen. • Cytosine (C), and thymine (T) are (Pyrimidines)=single ring Cytosine (C) Guanine (G) Thymine (T) Adenine (A)

  8. The structure of nucleotides Section 11.1 Summary – pages 281 - 287 • Thus, in DNA there are four possible nucleotides, each containing one of these four bases. • Base Pairing: • A-T (This pairing allows DNA to make • G-C a perfect copy of itself.) • These pairs are held together by two weak hydrogen bonds. =(Complementary base pairs) • Each base is held to the backbone with a stronger bond. The strong bond ensures that its sequence will not get mixed up.

  9. Section 11.1 Summary – pages 281 - 287 The structure of nucleotides • Nucleotides join together to form long chains, with the phosphate group of one nucleotide bonding to the deoxyribose sugar of an adjacent nucleotide. • The phosphate groups and deoxyribose molecules form the backbone of the chain, and the nitrogenous bases stick out like the teeth of a zipper.

  10. Section 11.1 Summary – pages 281 - 287 The structure of nucleotides • In DNA, the amount of adenine is always equal to the amount of thymine, and the amount of guanine is always equal to the amount of cytosine.

  11. Section 11.1 Summary – pages 281 - 287 The structure of DNA • In 1953, Watson and Crick proposed that DNA is made of two chains of nucleotides held together by nitrogenous bases. • Watson and Crick also proposed that DNA is shaped like a long zipper that is twisted into a coil like a spring. • Because DNA is composed of two strands twisted together, its shape is called double helix.

  12. Section 11.1 Summary – pages 281 - 287 Replication of DNA • Before a cell can divide by mitosis or meiosis, it must first make a copy of its chromosomes. • The DNA in the chromosomes is copied in a process called DNA replication. • Before DNA can replicate it must uncoil. • Without DNA replication, new cells would have only half the DNA of their parents.

  13. Section 11.1 Summary – pages 281 - 287 Replication of DNA Click this image to view movie (ch11)

  14. Section 11.1 Summary – pages 281 - 287 DNA Replication Replication of DNA Replication

  15. Section 11.1 Summary – pages 281 - 287 Copying DNA • DNA is copied during interphase prior to mitosis and meiosis. • It is important that the new copies are exactly like the original molecules.

  16. Roles of Enzymes • 1. Chemical bonds connecting the bases break due to enzymes called helicases. These move along the chain and the chain unwinds and separates. • 2. The DNA molecule separates into 2 complementary halves. (The areas where the double helix separates are called replication forks.) • 3. Free floating nucleotides join with the complementary nucleotides on the single strands. • 4. DNA polymerase (enzyme) binds to the separated chain and links the nucleotide back into a long strand. • DNA polymerase also has a proof reading role- in the event of a mismatched nucleotide it can replace it with a correct one.

  17. The Rate of Replication • Each human chromosome is replicated in about 100sections that are 100,000 nucleotides long, each section with its own starting point. • Replication forks work in concert, so that an entire human chromosome can be replicated in about 8 hours. • Replication forks tend to speed up replication. • Replication forks are more plentiful in eukaryotes (100) than in prokaryotes. (2)

  18. Section 11.1 Summary – pages 281 - 287 Copying DNA New DNAmolecule Original DNA Strand Free Nucleotides New DNAmolecule New DNA Strand OriginalDNAStrand Original DNA

  19. Section 11.1 Summary – pages 281 - 287 The importance of nucleotide sequences The sequence of nucleotides forms the unique genetic information of an organism. The closer the relationship is between two organisms, the more similar their DNA nucleotide sequences will be. Chromosome

  20. How Proteins are Made Chapter 10 Mrs. Fleck

  21. Section 11.2 Summary – pages 288 - 295 Genes and Proteins • The sequence of nucleotides in DNA contain information. • This information is put to work through the production of proteins. • Proteins fold into complex, three- dimensional shapes to become key cell structures and regulators of cell functions.

  22. Section 11.2 Summary – pages 288 - 295 Genes and Proteins • Some proteins become important structures, such as the filaments in muscle tissue. • Other proteins, such as enzymes, control chemical reactions that perform key life functions—breakingdown glucose molecules in cellular respiration, digesting food, or making spindle fibers during mitosis.

  23. Section 11.2 Summary – page 288 - 295 Genes and Proteins • In fact, enzymes control all the chemical reactions of an organism. • Thus, by encoding the instructions for making proteins, DNA controls cells.

  24. Section 11.2 Summary – page 2888- 295 Genes and Proteins • You learned earlier that proteins are polymers of amino acids. • The sequence of nucleotides in each gene contains information for assembling the string of amino acids that make up a single protein.

  25. Section 11.2 Summary – pages 288 - 295 RNA • RNA like DNA, is a nucleic acid. RNA structure differs from DNA structure in four ways. • First, RNA is single stranded—it looks like one-half of a zipper —whereas DNA is double stranded.

  26. Section 11.2 Summary – pages 288 - 295 RNA Ribose • The sugar in RNA is ribose; DNA’s sugar is deoxyribose. • RNA is Mobile and DNA is not mobile.

  27. Section 11.2 Summary – pages 288 - 295 RNA • Both DNA and RNA contain four nitrogenous bases, but rather than thymine, RNA contains a similar base called uracil (U). • Uracil forms a base pair with adenine in RNA, just as thymine does in DNA. Uracil Hydrogen bonds Adenine

  28. Section 11.2 Summary – pages 288 - 295 RNA • DNA provides workers with the instructions for making the proteins, and workers build the proteins. • The workers for protein synthesis are RNA molecules. • They take from DNA the instructions on how the protein should be assembled, then—amino acid by amino acid—they assemble the protein. • The entire process by which proteins are made is called Gene Expression

  29. Section 11.2 Summary – pages 288 - 295 RNA • There are three types of RNA that help build proteins. (mRNA, tRNA, rRNA) • Messenger RNA (mRNA), brings instructions from DNA in the nucleus to the cell’s factory floor, the cytoplasm. • On the factory floor, mRNA moves to the assembly line, a ribosome.

  30. Section 11.2 Summary – pages 288 - 295 RNA • The ribosome, made of ribosomal RNA (rRNA), binds to the mRNA and uses the instructions to assemble the amino acids in the correct order.

  31. Section 11.2 Summary – pages 288 - 295 Transcription A DNA strand RNA strand RNA strand C B DNA strand

  32. Section 11.2 Summary – pages 288 - 295 Transcription • In the nucleus, enzymes make an RNA copy of a portion of a DNA strand in a process called transcription. Click image to view movie (ch11)

  33. Section 11.2 Summary – pages 288 - 295 Transcription • The main difference between transcription and DNA replication is that transcription results in the formation of one single-stranded RNA molecule rather than a double-stranded DNA molecule.

  34. Section 11.2 Summary – pages 288 - 295 RNA • Transfer RNA (tRNA) is the supplier. Transfer RNA delivers amino acids to the ribosome to be assembled into a protein. Click image to view movie

  35. Section 11.2 Summary – pages 288 - 295 The Genetic Code • The nucleotide sequence transcribed from DNA to a strand of messenger RNA acts as a genetic message, the complete information for the building of a protein. • As you know, proteins contain chains of amino acids. You could say that the language of proteins uses an alphabet of amino acids.

  36. The Genetic Code • A code is needed to convert the language of mRNA into the language of proteins. • Biochemists began to crack the genetic code when they discovered that a group of three nitrogenous bases in mRNA code for one amino acid. Each group is known as a codon.

  37. Section 11.2 Summary – pages 288 - 295 The Genetic Code The Messenger RNA Genetic Code First Letter Third Letter Second Letter U A G C U U Phenylalanine (UUU) Serine (UCU) Tyrosine (UAU) Cysteine (UGU) C Cysteine (UGC) Phenylalanine (UUC) Serine (UCC) Tyrosine (UAC) A Stop (UGA) Serine (UCA) Stop (UAA) Leucine (UUA) G Leucine (UUG) Serine (UCG) Stop (UAG) Tryptophan (UGG) C U Arginine (CGU) Leucine (CUU) Proline (CCU) Histadine (CAU) Arginine (CGC) Proline (CCC) C Leucine (CUC) Histadine (CAC) A Proline (CCA) Arginine (CGA) Leucine (CUA) Glutamine (CAA) Arginine (CGG) G Glutamine (CAG) Proline (CCG) Leucine (CUG) A U Isoleucine (AUU) Threonine (ACU) Asparagine (AAU) Serine (AGU) C Serine (AGC) Asparagine (AAC) Isoleucine (AUC) Threonine (ACC) A Arginine (AGA) Isoleucine (AUA) Threonine (ACA) Lysine (AAA) G Arginine (AGG) Methionine;Start (AUG) Threonine (ACG) Lysine (AAG) G Glycine (GGU) U Valine (GUU) Alanine (GCU) Aspartate (GAU) Valine (GUC) Aspartate (GAC) Glycine (GGC) Glycine (GGC) C Alanine (GCC) A Glycine (GGA) Alanine (GCA) Glutamate (GAA) Valine (GUA) Glutamate (GAG) Glycine (GGG) Alanine (GCG) G Valine (GUG)

  38. Section 11.2 Summary – pages 288 - 295 The Genetic Code • All organisms use the same genetic code. • This provides evidence that all life on Earth evolved from a common origin.

  39. Section 11.2 Summary – pages 288 - 295 The Genetic Code • Some codons do not code for amino acids; they provide instructions for making the protein. • More than one codon can code for the same amino acid. • However, for any one codon, there can be only one amino acid.

  40. Section 11.2 Summary – pages 288 - 295 Translation: From mRNA to Protein • The process of converting the information in a sequence of nitrogenous bases in mRNA into a sequence of amino acids in protein is known as translation. • Translation takes place at the ribosomes in the cytoplasm. • In prokaryotic cells, which have no nucleus, the mRNA is made in the cytoplasm.

  41. Section 11.2 Summary – pages 288 - 295 Translation: From mRNA to Protein • In eukaryotic cells, mRNA is made in the nucleus and travels to the cytoplasm. • In cytoplasm, a ribosome attaches to the strand of mRNA like a clothespin clamped onto a clothesline.

  42. Section 11.2 Summary – pages 288 - 295 The role of transfer RNA • For proteins to be built, the 20 different amino acids dissolved in the cytoplasm must be brought to the ribosomes. • This is the role of transfer RNA.

  43. Section 11.2 Summary – pages 288 - 295 The role of transfer RNA Amino acid • Each tRNA molecule attaches to only one type of amino acid. Chain of RNAnucleotides Transfer RNA molecule Anticondon

  44. Section 11.2 Summary – pages 288 - 295 The role of transfer RNA • As translation begins, a ribosome attaches to the starting end of the mRNA strand. Then, tRNA molecules, each carrying a specific amino acid, approach the ribosome. • When a tRNA anticodon pairs with the first mRNA codon, the two molecules temporarily join together.

  45. Section 11.2 Summary – pages 288 - 295 The role of transfer RNA • Usually, the first codon on mRNA is AUG, which codes for the amino acid methionine. • AUG signals the start of protein synthesis. • When this signal is given, the ribosome slides along the mRNA to the next codon.

  46. Section 11.2 Summary – pages 288 - 295 The role of transfer RNA Ribosome mRNA codon

  47. Section 11.2 Summary – pages 288 - 295 The role of transfer RNA Methionine tRNAanticodon

  48. Section 11.2 Summary – pages 288 - 295 The role of transfer RNA • A new tRNA molecule carrying an amino acid pairs with the second mRNA codon. Alanine

  49. Section 11.2 Summary – pages 288- 295 The role of transfer RNA • The amino acids are joined when a peptide bond is formed between them. Methionine Alanine Peptidebond

  50. Section 11.2 Summary – pages 288 - 295 The role of transfer RNA • A chain of amino acids is formed until the stop codon is reached on the mRNA strand. Stop codon

More Related