Term
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Definition
Transformation experiments:
-DNA of one strain of bacteria can transfer genetic characteristics to related bacteria
Bacteriophage Experiments:
-Virus infects bacterium, only DNA from virus enters cell
-Virus reproduces and forms new viral particles from DNA alone |
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Term
| Many early geneticists thought genes were... |
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Definition
-Proteins
-Proteins are complex and variable
-Nucleic acids are simple molecules |
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Term
| Griffith's Transformation Experiment |
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Definition
Q: Can a genetic trait be transmitted from one bacterial strain to another?
A: Yes.
-They experimented on mice by injecting R(mouse lived) and S(mouse dies) cells when R and heat-killed S cells injected the mouse still died because the harmful S transmitted its trait to the un-harmful. |
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Term
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Definition
Q: What molecule is responsible for bacterial transformation?
A: DNA |
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Term
| Hershey-Chase Experiments |
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Definition
Q: Is DNA or protein the genetic material in bacterial viruses(phages)?
A: DNA.
-Bacterial viruses were grown in 35S to label protein, and 32P to label DNA
-Virus infect bacteria, agitate cells in blender, and separate by centrifugation
-35S protein is supernatant, bacteria in pellet contains 32P DNA
-Viral reproduction inside bacterial cells from pellet
-Cell lysis |
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Term
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Definition
-DNA model
Demonstrated:
-How info is stored in molecules structure
-How DNA molecules are templates for their own replication |
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Term
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Definition
-DNA is a polymer of nucleotides
Each nucleotide subunit contains:
-Nitrogenous base
Purines(A/G)
Pyrimidines(T/C)
-Pentose sugar(Deoxyribose)
-Phosphate group |
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Term
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Definition
Backbone:
-Alternating sugar and phosphate groups joined by covalent phosphodiester linkages
Phosphate group attatches to:
-5' C of one deoxyribose
-3' C of the next dexoyribose |
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Term
| The DNA building blocks consist of |
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Definition
-4 nucleotide subunits:
T
C
A
G |
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Term
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Definition
-2 polynucleotide chains associated as double helix
-Discovered by Rosalind through X-ray diffraction image of DNA
-Watson and Crick used her image as a way of discovering the double helix structure |
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Term
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Definition
Antiparallel:
-chains run in opposite directions
5' End:
-phosphate attached to 5' deoxyribose C
3' End:
-hydroxyl attached to 3' deoxyribose C |
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Term
| What is the active part of DNA |
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Definition
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Term
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Definition
H Bonding:
-between specific base pairs
-Binds 2 chains of helix
A with T:
-forms 2 H bonds
G with C:
-forms 3 H bonds |
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Term
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Definition
Complementary base pairing
-between A-T & C-G
-Therefore A=T, C=G
If base sequence of 1 strand is known, base sequence of other strand can be predicted |
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Term
| What are the 3 models of DNA replication? |
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Definition
Conservative:
-Copies entire strand of DNA
Semiconservative:
-Separates sides
-makes copies based on sides
Dispersive:
-Parts of original separate and fill in the gaps, cut up and rearrange |
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Term
| Meselson-Stahl Experiment |
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Definition
-Confirmed semiconservative
-Grew bacteria in 15N medium,transferred some to 14N medium
-Add CsCl DNA molecules move to positions where their density equals that of the CsCl solution
-15N on bottom, hybrid 14-15N in midle, 14N at top |
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Term
| Semiconservative Replication |
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Definition
Each daughter double helix consists of:
-1 original strand from parent molecule
-1 complimentary strand |
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Term
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Definition
-2 strands of double helix unwind, each is template for complementary strand
-Replication is initiated
DNA primase synthesizes RNA primer
-DNA strand grows
DNA polymerase adds nucleotide subunits |
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Term
| What enzymes are involved in DNA replication? |
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Definition
DNA helicase:
-open/split the double helix
Topoisomerases:
-prevent tangling and knoting |
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Term
| Bidirectional Replication |
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Definition
-Starting at origin of replication, and proceeding in both directions
Eukaryotic chromosome:
-May have multiple origins of replication, may replicate at many points at same time |
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Term
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Definition
-Always proceeds in 5'->3'
-Leading Strand (5'):
synthesized continuously
-Lagging Strand(3'):
synthesized discontinuously
forms short okazaki fragments
DNA primase synthesizes RNA primers
DNA ligase links okazake fragments |
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Term
| Replication in Bacteria and Eukaryotes |
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Definition
-Eukaryotic chromosome DNA contains multiple origins of replication
-DNA synthesis proceeds in both directions from each origin until adjacent replication bubbles eventually met. |
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Term
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Definition
-Proofread each new nucleotide against template nucleotide
Find errors in base pairing:
-remove incorrect nucleotide
-insert correct one |
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Term
| How do enzymes proofread and repair errors in DNA |
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Definition
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Term
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Definition
-Enzymes recognize incorrectly paired nucleotides and remove them
-DNA polymerases fill in missing nucleotides |
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Term
| What are the steps to nucleotide excision repair? |
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Definition
1. Repairs DNA lesions caused by sun or harmful chemicals
2. 3 enzymes
-Nuclease cuts out damaged DNA
-DNA polymerase adds correct nucleotides
-DNA ligase closes breaks in sugar-phosphate backbone |
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Term
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Definition
Eukaryotic chromosome ends:
-noncoding, repetitive DNA sequences
Shorten slightly with each cell cycle
Can be extended by telomerase |
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Term
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Definition
-May be caused by absence of telomerase activity
-Cells lose ability to divide after a limited number of cell divisions |
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Term
| How do cancer cells use telomerase? |
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Definition
-Cancer cells have telomerase to maintain telomere length and possibly resists apoptosis
-Cancers such as:
breast, lung, colon, prostrate, pancreas |
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