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11.1 Genes are made of DNA. Griffith Experiment. Viral DNA Background. Virus – a package of nucleic DNA wrapped in a protein shell that must use a host cell to reproduce, they are not considered living organisms Bacteriophage – virus that infects bacteria
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Viral DNA Background • Virus – a package of nucleic DNA wrapped in a protein shell that must use a host cell to reproduce, they are not considered living organisms • Bacteriophage – virus that infects bacteria • There must be something in a virus that allows it to transform bacteria
Question 1 & 2 • Explain how experiments done by Griffith, Avery & Hershey and Chase supported that genes are made of DNA? [4 points] 2. Identify the parts of DNA and how the double helix is put together (bases)? [4 points]
11.2 Nucleic acids store information in their sequences of chemical units
Nucleotides • Nucleotides are individual units of DNA that compose the whole chain • Each nucleotide consists of: a phosphate a suger (Deoxyribose) One of four nitrogen base (A,T,C,G)
Rosalind Franklin & Maurice Wilkins 1950’s photographs of the DNA molecule using X-ray crystallography which showed the shape to be a helix
Erwin Chargaff • 1951, proved that the % of A = T and % of G = C
Watson &Crick • 1953, used data from the other scientists and built models to finally figure out the exact structure of DNA • 1962 won the nobel prize in Medicine
11.3 DNA replication is the molecular mechanism of inheritance
DNA Replication • Enzymes are protein molecules that catalyze chemical reactions in a cell – usually any protein ending in “ase” is an enzyme • Helicase- unwinds DNA • DNA Polymerase 3- Adds complementary nucleotide • DNA Polymerase 1- Checks for error
11.4 A gene provides the information for making a specific protein
Beadle and Tatum • Beadle and Tatum discovered when looking at mutant Neurospora crassa (bread mold) • Individual gene produces a specific enzyme • One gene - one polypeptide (combinaiton of amino acids)
Deoxyribose sugar A,T,C,G Double strand Nucleus Ribose sugar A,U,C,G Uracil pairs with adenine Single strand Nucleus to cytoplasm DNA & RNA
Steps of Transcription 1. DNA double helix unwound and separated by RNA polymerase 2. RNA polymerase adds RNA nucleotides together, making a single strand of mRNA which is complementary to 1 strand of the DNA
Steps of Transcription 3. mRNA is processed (modified) before leaving the nucleus • introns (non coding regions) are cut out of the mRNA • exons (coding regions) are “spliced” together to form the final mRNA product 4. Introns are cut out and exons are spliced together to form the final copy of messenger RNA (mRNA)
Steps of Translation 1. mRNA leaves the nucleus and is transported to the ribosome where translation takes place 2. Ribosome holds onto the mRNA, the mRNA codon AUG is located in the P site of the ribosome 3. tRNA carries an amino acid to the P site of the ribosome 4. Another tRNA carries the next amino acid to the A site of the ribosome
Steps of Translation 5. Two amino acids are joined together with a peptide bond 6. tRNA in the P site leaves 7. Ribosome moves along the mRNA until the next codon is located in the A site (the tRNA which was located in the A site is now in the P site and is holding the peptide chain) 8. tRNA carries the next amino acid to the A site
Steps of Translation 9. New amino acid is joined to the peptide chain (the polypeptide is made of 3 amino acids) • tRNA in the P site leaves 11. Process continues until a stop codon appears in the A site of the ribosome 12. Polypeptide is now complete
Rules for translation 1. Codon is a three-base “word” that codes for one amino acid 2. Determine the amino acid coded for by an mRNA codon use the genetic code 3. Genetic code is universal – all species use the same genetic code, the same 20 amino acids are used in all living organisms
How mutations affect genes 1. A mutation is any change in the nucleotide sequence of DNA. 2.Two categories of mutations a. Base substitutions (point)– replacement of one nucleotide with another i. This can change the protein or not change the protein b. Base insertions or base deletions (frameshift) – addition of an extra nucleotide or subtracting a nucleotide i. Have more effect on the protein than a substitution
What causes mutations? 1. Mistakes during DNA replication can cause mutations 2. Mutagens – physical or chemical agents that cause mutations a. Physical mutagens – high energy radiation, X-rays, Ultraviolet light b. Chemical mutagens – chemicals that are similar to DNA bases and cause incorrect base-pairing
Body Cells Cancers Gametes Birth defects Genetic disorders Mutations Effects
Ch. 11 Test • Vocabulary • DNA & RNA structure • Replication, transcription, translation- content and problems • Scientists & experiments involved • Mutations & mutagens- types and effects
13.2 Biologists can engineer bacteria to make useful products