Presentation on theme: "DNA: Structure and Function. The DNA Revolution 1940s-1960s Griffith & Avery—DNA transformed pneumococcus bacteria. Encouraged the study of prokaryotic."— Presentation transcript:
DNA: Structure and Function
The DNA Revolution 1940s-1960s Griffith & Avery—DNA transformed pneumococcus bacteria. Encouraged the study of prokaryotic chromosomes. Hershey and Chase—Bacteriophage experiment. DNA from viruses is injected to host bacteria cells.
Griffith and Avery
Hershey & Chase
The Search for the Structure of the DNA Molecule 1951—Rosalind Franklin—X-ray crystallography Chargaff—Chargaff’s rules. Ratio of nitrogenous bases in DNA. Complimentary bases. Watson & Crick--1953
Watson & Crick Model of DNA Nucleotides Sugar—Deoxyribose Phosphate Group Nitrogenous Bases Adenine & Thymine are complementary. Cytosine and Guanine are complimentary. Purines—Adenine & Guanine Pyrimidines—Cytosine & Thymine 5’ End—Phosphate side 3’ End—Other side
Watson & Crick Model DNA is composed of 2 chains of nucleotides that form a double helix shape. The two strands are antiparallel. The backbone of the DNA molecule is composed of alternating phosphate groups and sugars. The complimentary nitrogenous bases form hydrogen bonds between the strands. A is complimentary to T and G is complimentary to C.
DNA Functions 1. Storage of genetic information 2. Self-duplication & inheritance. 3. Expression of the genetic message. DNA’s major function is to code for proteins. Information is encoded in the order of the nitrogenous bases.
Chromosomes Prokaryotic Circular Very small 1 chromosome per cell Some enzymes and proteins are associated with the DNA. Not housed in a nucleus. Eukaryotic Linear Fairly long Several chromosomes per cell. Histone proteins---”spools”. Same in all eukaryotes Housed in a nucleus. Nucleosome—2 loops of DNA wrapped around 8 histone proteins. Unity theme.
Summary Describe the structure and function of DNA.
DNA Replication DNA replicates in a semiconservative way 1 strand is the “leading strand” (3’ 5’) 1 strand is the “lagging strand” (5’ 3’)
DNA Replication Steps 1.Helicase (protein) unzips the DNA 2.DNA polymerase (protein) binds to the strands 3.DNA polymerase adds the floating nucleotides to the new DNA strand. 4.2 new strands are made
Summary Describe the process of DNA Replication
Transcription RNA polymerase Messenger RNA mRNA Unzipping of DNA helix. Sense strand or template strand Codons Genetic code
Translation Vocabulary 1. Amino Acid- The basic building block of proteins 2. tRNA- a RNA molecule that carries the amino acid to the ribosome 3. codon- a set of 3 nucleotides used to code for an amino acid 4. polypeptide- a string of many molecule (ex: protein is a polypeptide of amino acids) 5. P site- where the tRNA detaches leaving behind the amino acid 6. A site- where the tRNA arrives
Translation Steps: 1. mRNA enters the cytoplasm from the nucleus 2. mRNA finds a ribosome 3. Ribosome starts translation by using the tRNA that carries Methionine (AUG) 4. Protein chain elongates 5. Stop codons terminates the translation of protein elongation