Term
| who was the discovere of nucleic acid? |
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Definition
friedrich miescher (1844-1895)
he took pus from bandages and seperated the nuclei form the white blood cells. he found a substance rich in phosphorus and nitrogen. he called the acid phosphorus rich part nucleic acid |
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Term
t/f
chromsomes contain DNA and protein? |
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Definition
| true - the genetic material is in the DNA |
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Term
| what did griffith's transformation experiments in 1928 with lethal/non-lethal forms of streptococcus pneumoniae discover? |
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Definition
| the transforming principle - mixing dead virulent forms of s.pneumoniae with live harmless versions gave rise to a live disease causing version |
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Term
| in Griffith's transformation experiments what was the physiological different between the S (virulent ) and the R (harmless) version of S. pneumoniae? |
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Definition
the virulent (S) version had a polysaccharide coat which prevented detection from the hosts immune system.
the R (harmless) version lacked this coat thus was recognised and eliminated by host defence system |
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Term
| what did Avery, McLeod and MacCarty do in 1944? |
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Definition
they established the chemical properties of the transforming principle - it was resistant to proteases, lipases, ribonucleases so not them.
ethanol insoluble - so not carbohydrate
high Mr like DNA and positive reaction to dische test for DNA |
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Term
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Definition
bases in DNA are not 1:1:1:1 ratio. they obey a strict rule
30.9% A ~ 29.4% T
19.8% C ~ 19.9% G
roughly the same percentages of the base pairs |
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Term
| when was the hershey-chase experiment and what did it show? |
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Definition
| in 1952. it showed that bacteriophage injects DNA (not protein) into bacterial cell. they labelles B'phage protein and DNA seperately and fused with E.coli. when they centrifuged them. DNA tags were in the cells (pellet) and protein tags were in the supernatant |
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Term
| in Hershey-Chase experiement (1952) what did they tag protein and DNA with? |
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Definition
protein - 35S sulphur
DNA - 32P phosphorus |
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Term
| when a bacteriophage infects a bacterium does its protein coat insert into the host of is it left outside? |
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Definition
| left outside only viral DNA is injected into host bacterium |
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Term
| Watson and Crick 1953 what did they do? |
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Definition
| solve the structure of DNA and build a double helix with help from Rosalind Franklin |
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Term
| whats so special about Rosalind Franklin? |
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Definition
| she deduced that the sugar phosphate back bone of the double helix would be on the outside and the nitrogenous bases would be on the inside |
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Term
| 3 building blocks of DNA? |
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Definition
| pentose sugar, nitrogenous base (4 types) and a phosphate group |
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Term
| on DNA which carbon is the phosphate group attached to? |
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Definition
|
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Term
| Purines consist of how many rings? and which bases are purines? |
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Definition
2 rings
Guanine and Adenine are purine |
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Term
| Pyramidines consist of how many rings and which bases are pyramidines? |
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Definition
1 ring
Cytosine and Thymine are pyramidines |
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Term
| which direction does DNA follow? |
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Definition
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Term
| watson and crick used trial and error in developing their model for the double helix. what happened when they pair 2 pyramidines then 2 purines? |
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Definition
2 pyramidines were too narrow
2 purines were too wide
purine and pyramdine width was consistent with the x-ray data |
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Term
| in the base pairing of A=T AND G=C which base pair is stronger and why? |
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Definition
| G=C is stronger because it has 3 hydrogen bonds compared to A=T which has 2 hydrogen bonds |
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Term
| how do the 2 strands of DNA run? |
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Definition
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Term
| what did watson and crick suggest about the copying mechanism of dna? |
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Definition
| they suggested one strand acted as a template for a complementary strand |
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Term
| is DNA replication conservative or semi-conservative? |
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Definition
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Term
| DNA replication is catalysed by which enzyme? |
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Definition
|
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Term
| on which end of the DNA/RNA can DNA Polymerase add nucleotides to? |
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Definition
|
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Term
| how does DNA replication begin? |
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Definition
| as a bubble that turns into a replication fork |
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Term
| in which direction are daughter strands synthesised? |
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Definition
| 5 >3 (because they are complimentary to the 3>5 strand) |
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Term
| what do okazaki fragments do? |
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Definition
| they show direction of growth of daughter strand for DNA Polymerase |
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Term
| in dna replication what is the name of the strand that isnt leading? |
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Definition
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Term
| on which strand lead or lagging, would you find the formation of okazaki fragments? |
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Definition
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Term
| which enzyme synthesises new primers in the lagging strand? |
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Definition
|
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Term
| describe the steps in the lagging strand to form a daughter strand |
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Definition
| new RNAprimers synthesised by Primase are made, DNA polymerase III extends the dna template until one primer joins another primer. DNA polymerase I removes the RNA primer and DNA ligase joins the gaps up...ta da the daughter strand is complete! |
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Term
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Definition
| unwinds the dna helix - opens it up |
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Term
| what do single stranded binding proteins do? |
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Definition
|
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Term
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Definition
| synthesises the RNA primers needed for initiation of DNA synthesis |
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Term
| what does DNA Polymerase III do? |
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Definition
| extends the DNA/RNA strand from the 3' end, copying the template |
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Term
| what does DNA Polymerase I do? |
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Definition
| removes RNA primer and fills in gaps between okazaki fragments |
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Term
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Definition
| seals the gaps between okazaki fragments |
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Term
| how accurate is DNA replication? |
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Definition
mistakes can occur 1 in 10,000 bases
but errors in completed dna are 1 in a billion |
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Term
| why are mistakes so rare in dna? |
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Definition
| due to the ability of DNA Polymerase to proof read |
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Term
| what does DNA Polymerase do when it spots an incorrect match? |
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Definition
| it uses its 3'>5' exonuclease activity to excise the incorrect nucleotide |
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Term
| what happens when an error does occur in dna replication? |
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Definition
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