From DNA to Proteins Ch. 8

DNA Genetic Code- program of the cell which relates to heredity How did scientists learn that the genetic code is DNA? Frederick Griffith (1928)- discovered transformation- process by which genetic material is absorbed from the environment and incorporated into the bacteria's DNA

Griffith’s Experiment-finding the transforming principle injected mice with noncapsulated bacteria (R)- mice live injected mice with capsulated bacteria (S)- mice died injected mice with heat killed capsulated bacteria(S)- mice lived injected mice with heat-killed capsulated (S) and noncapsulated bacteria (R)- mice died

Griffith’s Experiment

Identifying DNA as the transforming principle Avery, McCarthy and MacLeod (1944)- proved DNA was transforming factor used protein destroying enzymes and transformation occurred used DNA destroying enzymes and no transformation occurred

Hershey and Chase confirm DNA is genetic material Hershey and Chase (1952)- studied bacteriophages (viruses which infect bacteria) and proved that DNA was the genetic info. tagged protein coat of virus with radioactive sulfur tagged DNA of virus with radioactive phosphorus introduced virus to bacteria and found that the radioactive P entered the bacteria

Hershey and Chase

Structure of DNA Composed of nucleotides 5-C sugar (deoxyribose) phosphate group nitrogenous base purines = adenine and guanine pyrimidines = cytosine and thymine

Structure of DNA phosphate group nitrogen-containing base deoxyribose (sugar) nitrogen-containing base

Structure of DNA

The Base Pair Rule Chargaff- determined that adenine bonds to thymine and cytosine bonds to guanine same 4 bases are used by all organisms but in different quantities and order

The Base Pair Rule hydrogen bond covalent bond

The Double Helix Watson and Crick with the help of Wilkens and Franklin determined that DNA is a double helix Franklin’s x-ray crystallography work was extremely important they won the Nobel Prize in 1962 (except for Franklin who died before the award was given)

The Double Helix

DNA Replication DNA Replication- process by which DNA makes a copy of itself in order to produce two identical cells 1. DNA is uncoiled with enzymes 2. DNA polymerase- enzyme which then bonds the complementary nucleotides together 3. Each new DNA molecule has one original and one new strand (semiconservative model)

DNA unzips in both directions DNA Replication DNA unzips in both directions nucletodies

DNA Replication DNA polymerase new strand nucleotide

DNA Replication original strand new strand Two molecules of DNA

RNA RNA- nucleic acid which acts as a messenger between DNA and the ribosomes for protein synthesis Central Dogma- information flows from DNA to RNA

Structure of RNA Structure- single stranded 5-Carbon sugar (ribose) phosphate group nitrogenous base purines- adenine and guanine pyrimidines- cytosine and uracil

Transcription Transcription- process by which information is transferred from DNA to RNA in sets of three nucleotides (codon) only the part of DNA which has the code for the protein is copied messenger RNA (mRNA)- copies and carries information out of nucleus to ribosome

Transcription introns are genes not used to make a protein (these get cut out before mRNA leaves the nucleus), exons are genes used to make a protein

Transcription start site nucleotides transcription complex

RNA polymerase moves along the DNA Transcription DNA RNA polymerase moves along the DNA

Transcription RNA

Translation Translation- decoding of mRNA in order to form proteins (assisted by transfer RNA- tRNA and ribosomal RNA - rRNA) tRNA reads in sets of 3 called the anticodon

Translation codon for methionine (Met) leucine (Leu)

Translation The genetic code matches each RNA codon with its amino acid or function.

Translation A change in the order in which codons are read changes the resulting protein.

Translation Machinery tRNA

Translation Machinery Ribosome

Translation

Translation

Translation

Mutations Random changes to DNA Point mutation- one nucleotide is substituted Frameshift mutation- insertion or deletion of a base resulting in a shift as to how the codon is read Mutagens- agents which can change the DNA (UV light, industrial chemicals etc.)

Mutations mutated base

Mutations