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DNA Structure

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Angie Dobberfuhl

on 8 October 2012

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Transcript of DNA Structure

DNA structure DNA code DNA as hereditary information The structure of DNA Sequence of a Gene TRANSCRIPTION Replication TRANSLATION http://www.dnai.org/timeline/index.html http://www.dnai.org/timeline/index.html Watson and Crick wrote this paper Wilkins wrote this paper DNA code is read to make mRNA RNAs make Protein Structure of DNA 1869 1952 Meischner Chemical discovery of nuclein (DNA) in nucleus of every cell Thought to be for storage of Phosporus First Isolated from dirty bandages 1928 Griffith 1944 Avery Used enzymes on S strain to break down Sugar coat, Protein, RNA and DNA DNA enzymes were the only ones to stop transformation Used S+R bacterial strains in test tuubes A transforming factor can change organisms What is the transforming factor??? Pneumonia has 2 forms Heat killed S=harmless S=deadly Rough= harmless Heat Killed S+R=deadly One Sulfur labeled protein Phosphate labeled DNA made bacteria radioactive Radioactively labeled bacteriophages Hershey and Chase One Phosphate labeled DNA Watson and Crick and Franklin and Wilkins pieces of evidence DNA is made of nucleotides A-T and G-C Nucleotides fit
together x-ray crystallography shows double helix Why would people have thought that protein was the hereditary information rather than DNA?
Why should scientists have believed that the DNA (rather than protein) from the heat-killed bacteria was the molecule that changed harmless pneumonia bacteria into dangerous pneumonia bacteria?
Why was it important to Watson and Crick that Questions to consider Hershey and Chase supported the hypothesis that DNA was the molecule of heredity?
Can you do science without strictly using the scientific method? Why?
Which phase of the cell cycle would be affected if your DNA polymerase enzyme stopped working correctly?
How is it possible for 4 bases to code for many different proteins? Questions to consider DNA is like a spiral staircase The Double Helix Base pairing When the bases pair to make the ‘steps’ they pair in the same way The railing is the phosphate/sugar ‘backbone’ The stairs are two bases

connected by hydrogen bonds DNA Replication Starts at a specific site (ori)

Is ‘unzipped’ and untwisted by enzymes

Proteins hold the DNA strands apart

Enzymes, DNA Polymerase copy the DNA

The replication occurs in two directions moving in opposite directions

until two new copies are made REPLICATION
the process by which DNA makes copies of itself DNA sequence is the sequence of bases in the gene

The DNA sequence has a code for amino acids

This code has a start, a stop and information in between

The code is based on triplets

Every three nucleotides code for one amino acid

All organisms have the same code

http://www.pbs.org/wgbh/nova/genome/expl_09_gene.html DNA code DNA Language TAC CCC GGG TCT ACG ACT Capital letter Period ATT question mark
ACC exclamation point I can see one DNA ! AUG RNA Language GGG CCC AGA UGC UGA MET
methionine GLY
glycine PRO
Proline ARG
arginine CYS
cystine STOP
Amino acid Protein language What might happen to a protein if the stop codon in the DNA had a mistake?
What might happen to a protein if the start codon in the DNA had a mistake?
Why is mRNA made?
What might happen if a Transcription factor protein was made incorrectly?
What might happen if a tRNA was unable to find its amino acid? Questions to Consider If a ribosomal protein was made incorrectly, what might happen?
Why do you think RNA has Uracil rather than Thymine? Questions to Consider Transcription Translation Transcription Factor Initiation Factor RNA Polymerase often proteins; used to regulate genes 'read' the DNA and help open the helix reads the DNA adding RNA nucleotides starts the RNA Polymerase What is needed Where is it made In the Nucleus What is needed? mRNA tRNA Ribosome (rRNA) Carries the code for the protein in nucleotides Carries the anticode to read the mRNA and the amino acids (1 per tRNA) Holds the mRNA and tRNAs Creates the peptide bonds between the amino acids Where is it made? In the cytoplasm How is it regulated? mRNA can be destroyed mRNA can be blocked mRNA can be changed How is it regulated?

Transcription factors can be destroyed More than one transcription factor means you can transcribe different genes mRNA can be changed after transcription
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