3What carries hereditary information? By the 1940s, scientists knew that chromosomes carried genes.They also knew that chromosomes were made of DNA and protein.They did NOT know which of these molecules actually carried the genes.Since protein has 20 types of amino acids that make it up, and DNA only has 4 types of building blocks, it was a logical conclusion.Most Scientists thought protein carried genes
6So…he knew that DNA carried hereditary information! Avery’s Experiment1. Avery repeated Griffith’s experiments with an additional step to see what type of molecule caused transformation.3. When Avery added enzymes that destroy DNA, no transformation occurred.So…he knew that DNA carried hereditary information!2. Avery used enzymes to destroy the sugars and transformation still occurred—Sugar did not cause transformation.Avery used enzymes to destroy lipids, RNA, and protein one by one. Every time transformation still occurred—none of these had anything to do with the transformation.
7Hershey-Chase Experiment The experiment involved viruses to see if DNA or protein was injected into the bacteria in order to make new viruses.One group of viruses was infected with radioactive protein and another group with radioactive DNA.Then the viruses attack the bacteria.Radioactive DNA shows up in the bacteria, but no radioactive protein.
9Chargaff’s RulesThe amount of adenine (A) equals the amount of thymine (T).The amount of cytosine (C) equals the amount of guanine (G).
10Rosalind Franklin Took X-ray pictures of DNA. The photos revealed the basic helix, spiral shape of DNA.
11Maurice Wilkins Worked with Rosalind Franklin. Took her x-ray photos and information to Watson and Crick
12Watson and CrickUsed Franklin’s pictures to build a series of large models.Stated that DNA is a double-stranded molecule in the shape of a double helix, or twisted ladder.Won the Nobel Prize for their work in 1962.
13Basic DNA Structure A nucleotide is the monomer of DNA PA nucleotide is the monomer of DNAA nucleotide is made ofa sugar called deoxyribosea phosphateand a base (ATCG)SACSPSPT
14Deoxyribose Simple sugar molecule like glucose that has 5 carbons The five carbons are numbered clockwise starting from the first one after the oxygen
15PhosphateThe negatively charged phosphate bonds to the 5’ Carbon of the deoxyribose.
17Bases There are two main types of bases purines and pyrimidines. Purines have two rings in their structure.Adenine and guanine are purines.Pyrimidines only have one ring.Thymine and Cytosine are pyrimidines.PyrimidinesPurines
18Basic DNA StructurePTo form one strand of DNA, the phosphate of one nucleotide covalently bonds to the 3’ Carbon of the deoxyribose from another nucleotide.SACSPSPT
19The two strands of DNA are held together by hydrogen bonds PSTSPACSPGSPSPTSPAThe two strands of DNA are held together by hydrogen bonds
20Base PairsThe nucleotides that bond together by their bases are called base pairs.Adenine only bonds to ThymineGuanine only bonds to Cytosine
31DNA Polymerase Adds New Nucleotides GSPACSPGSPSPTSPA
32Are the two copies of DNA the same? Why would it be important for the two copies of DNA to be the same?
33What is a Gene? A gene is a code found in DNA Genes code for proteins that give people their traits.
34How does DNA code for so many traits with only 4 bases? Can you spell 20 words with the letters A, T, C and G?Each combination of bases codes for a different amino acid.Putting the 20 amino acids in different orders makes different proteins.
38RNA Single-stranded nucleic acid Made of nucleotides Has ribose instead of deoxyriboseHas uracil instead of thymine
39Protein Synthesis Two Steps to making a protein Transcription Writing DNA codeTranslationDecoding DNA’s message into a protein
40TranscriptionTranscription happens in the nucleus where the DNA is.
41Transcription DNA’s code is copied by messenger RNA (mRNA). mRNA has complementary bases to the DNA (Remember RNA has a U instead of T).Three bases of mRNA make a codon.
42TranslationAfter mRNA is made in Transcription, the mRNA goes to the ribosome where the protein is made.
43Translation Translation begins at the start codon (AUG) of mRNA. Then each codon codes for an amino acid in a protein that is brought in by a tRNA (transfer).tRNA has an anticodon with complementary bases to the mRNA codon.Translation is terminated by stop codon.
44Which Amino Acid does each codon code for? GGUGlycineAAALysineCUGLeucineUGGTryptophan
45Mutations Mutation-alteration in DNA Mutagens-physical and chemical agents that mutate DNADeletion-mutation caused by deleting DNA that should be thereInsertion-mutation caused by inserting DNA that should not be thereSubstitution-mutation caused by substituting DNA
46Gene Regulation Genes are not expressed all the time. Some genes are usually on, but can be turned off by repressors when they are not needed.Some genes are usually off, but they can be turned on by enhancers when they are needed.