Transcription Translation.notebook

Transcription Translation.notebook
March 13, 2013
Do Now
Explain the process between DNA and proteins. I. 1909 Archibald Garrod's Experiment A. Suggested a relationship between genotype and phenotype of individuals
B. Researched the autosomal recessive disorder alkaptonuria (disorder where urine appears black due to a chemical called alkapton) 1. Hypothesized that normal individuals have the enzyme to break down alkapton in their urine
2. Individual that have alkaptonuria cannot make that enzyme
3. "inborn errors in metabolism"
C. Later research confirmed this idea that cells make and break down biologically important molecules via a set pathway.
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Transcription Translation.notebook
March 13, 2013
George Beadle and Edward Tatum
http://www.dnalc.org/resources/nobel/beadle_tatum.html
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Transcription Translation.notebook
March 13, 2013
Do Now
Briefly explain the importance of Beadle and Tatum's experiment.
HMWK: DNA Extraction Lab Test on Friday (3/8) R/O 10.9 ­ 10.10 due on Friday (3/8)
II. 1941 ­ George Beadle and Edward Tatum
A. Worked with Neurospora crassa (bread mold)
B. Studied strains of the bread mold and mutated several strains
C. Strains could grow in a complete medium but could not grow in a minimal medium
D. Then further analyzed the mutant strains. Grew them in minimal media supplemented with various substances
1. Found mutant mold could grow in minimal media supplemented with arginine (amino acid)
2. Mutation in the genetic pathway that creates an essential molecule the mold required to survive (arginine)
3. Mutation in enzyme that help to produce arginine
E. Concluded that one gene codes for one enzyme
(One gene ­ one protein, one gene ­ one polypeptide)
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Transcription Translation.notebook
March 13, 2013
III. Central Dogma
A. DNA (gene) mRNA (transcription)
B. mRNA Protein (translation)
IV. Transcription (first step in creation of proteins)
A. Goal: Take a gene from DNA and make a mRNA copy
B. Location: Nucleus (eukaryotic cell)
C. Steps to Transcription:
1. Initiation: RNA Polymerase binds to the promoter (start sequence) of a gene on a DNA strand
2. Elongation: RNA Polymerase build a new RNA strand off the template strand of DNA. a. Hydrogen bonds allow the complementary base pairs to be held in place. b. RNA peels away from DNA template. 3. Termination: RNA Polymerase reaches termination (end of a gene) sequence of DNA. RNA Polymerase detaches from RNA and DNA strands.
http://www­class.unl.edu/biochem/gp2/m_biology/animation/gene/gene_a2.html
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Transcription Translation.notebook
March 13, 2013
Let's Try These...
• 1. Where in the cell does transcription occur?
• 2. What nucleic acids are involved in the process of transcription?
• 3. What is the importance of transcription?
• 4. In transcription, how come the whole DNA molecule is not copied into mRNA?
• 5. How does one gene differ structurally from another?
• 6. Because one gene differs from another, what molecules in the cell will also be different?
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Transcription Translation.notebook
March 13, 2013
Do Now
RNA Processing
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Transcription Translation.notebook
March 13, 2013
V. RNA Processing (eukaryotes only)
A. Location: Nucleus ­ after transcription
B. Parts of RNA Processing:
1. 5' Cap is added (methylated guanine molecule)
2. Polyadenylation (50 ­ 250 adenine molecules added to 3' end) ~ Poly A Tail
3. Purpose for Cap and Tail
a. facilitate the export of mRNA from nucleus
b. protect mRNA from attack from cellular enzymes
c. help ribosome bind to mRNA
4. RNA Splicing: process where introns are removed and exons are adhered together
a. intron: non coded regions
b. exons: coding regions (will be translated)
c. process is catalyzed by small RNA molecules and proteins (sometimes by RNA itself!)
d. Purpose of introns and exons: eukaryotes have DNA sequences that code for proteins that are not continuous and allow for evolution of new proteins (different proteins produced from same gene ­ alternative splicing) http://highered.mcgraw­hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/
0072437316/120077/bio30.swf::How%20Spliceosomes%20Process%20RNA
HMWK: bring book to class on MONDAY
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Transcription Translation.notebook
March 13, 2013
Translation
Translation ­ the process of creating a polypetide from mRNA
Location:
Three parts to translation: initiation, elongation, termination
Ribosome Structure:
­ made of two subunits (large and small)
­composed of rRNA and several small proteins
­eukaryote and prokaryote ribosomes differ in size but not in function
­3 grooves on ribosome (A, P, E)
­A site: tRNA binds
­P site: polypeptide formation
­E site: exit site
A. Steps to initiation:
1. mRNA leaves the nucleus through nuclear pores 2. the 5’ end of mRNA binds to small subunit on ribosome
3. initiator tRNA binds to the start codon in the P site of ribosome and large subunit binds to the small subunit Codon: group of 3 nucleotides on the messenger RNA that specifies one amino acid (64 different codons)
Anticodon: Group of 3 unpaired nucleotides on a tRNA strand. (binds to mRNA codon)
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Transcription Translation.notebook
March 13, 2013
tRNA Structure:
­composed of a single polynucleotide chain (80 nucleotides) folded over upon itself creating double stranded sections
­matches up amino acids with proper codon
­contains the anticodon that pairs with the codon
B. Elongation
1. Codon recognition: the anticodon of incoming tRNA pairs with the codon on A site
2. Peptide bond formation: polypeptide separates from tRNA and forms a peptide bond with the AA in A site
3. Translocation: ribosome moves one triplet over and uncharged tRNA now goes to the E site and exits the tRNA
C. Termination
1. Process continues until a stop codon is reached (UGA, UAG, UAA)
2. Release factors bind to ribosome and cause ribosome subunits, mRNA, and polypeptide chain to be released
http://www­class.unl.edu/biochem/gp2/m_biology/animation/gene/gene_a3.html
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Transcription Translation.notebook
March 13, 2013
Mutations
• A permanent change that occurs in a cell’s DNA is called a mutation. • Three types of mutations:
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Point mutation
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Insertion
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Deletion
• Point Mutation (substitution): A change in just one base pair
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Missense Mutation: amino acid is change
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Nonsense Mutation: amino acid is changed to a stop codon
• Frameshift Mutation:Causes the reading frame to shift to the left or the right
• Insertion: Addition of a nucleotide
• Deletion: Removal of a nucleotide
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Transcription Translation.notebook
March 13, 2013
Causes of Mutations
• Mutations can happen spontaneously
• Mutagens: Certain chemicals or radiation that can cause DNA damage
• Causes bases to mispair and bond with the wrong base
• High­energy forms of radiation, such as X rays and gamma rays, are highly mutagenic.
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