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week 5 Flashcards

(53 cards)

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1
Q

streptococcus pneumoniae

A

bacteria that can invade and infect lungs causing pneumonia

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2
Q

two strains of SP

A

defined by serotypes
serotype II
serotype III

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3
Q

serotype II

A

no capsule- ‘rough colony’
non pathogenic
mice could fight off infection with immune system and survive infection when injected into mice

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4
Q

serotype III

A

capsule
‘smooth’ colony
pathogenic in mice
when injected into mice, they colonise the lungs, infect the mouse and eventually the mouse dies

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5
Q

heat killed smooth type III + rough type II

A

mouse dies from pneumonia
bacteria isolated with type III capsules from lungs of micem

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6
Q

smooth type iii

A

mouse dies from pneumonia
bacteria isolated with type III capsules from lungs of mice

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7
Q

transforming principle

A

discovered by griffith 1928
some property of the dead, heat killed smooth type III bacteria can transform the live, rough type II bacteria

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8
Q

modern take on transforming principle

A

transformation occurs because DNA is released from heat killed smooth type bacteria
taken up by living rough type bacteria and incorporated into their genome
changing their properties

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9
Q

transformation in vitro

A

dawson 1931
hear killed IIIS cells will transform living IIR cells in vitro
living IIIS cells recovered without injection into mice
makes the process of identifying the transforming principle simpler

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10
Q

Avery MacLeod and McCarty

A

1944
discovered transforming principle was DNA

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11
Q

Avery, MacLeod and McCarty experiment

A

used 75L heat killed IIIS cells to give a soluble extract containing the transforming principle
successively removed different components:
- removed lipids (extract still alive)
- removed protein (extract still alive)
- removed polysaccharide (extract still alive)
only DNA remaining (extract still alive)

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12
Q

AMM final experiment

A

confirmed in final experiment where they treated with an enzyme DNAse with breaks down DNA and the activity was lost

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13
Q

AMM rejection

A

not universally accepted
thought to be too simple a molecule to change the phenotype of a bacteria in the way the transforming principle did

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14
Q

AMM conclusion

A

confirms DNA as transforming principle
DNA has potential to change properties of a living organism
does not fully demonstrate that biological organisms use nucleic acids as their genetic material

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15
Q

Hershey-chase exp

A

demonstrated that the genetic material is DNA
worked on bacteriophage T2 (virus that infects bacteria)

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16
Q

hershey chase exp explained

A

2 batches of phage labelled with different radioisotopes
DNA labelled radioactively
centrifuged
heavy cells go to bottom
forms pellet
32P was mainly in the pellet
only the DNA is passed into cells on infection as the genetic material

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17
Q

evidence for DNA structure

A

x ray diffraction
Chargaff’s laws (1949-1953)
nucleotide structure known

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18
Q

x ray diffraction

A

DNA is helical with repeating units of 3.4 A (distance between base pairs) and 34A (distance taken by one turn of the helix)

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19
Q

chargaff’s laws

A

1949-1953
total pyrimidines (T,C)= total purines (A,G)
[T]=[A] and [C]=[G]
established based on chemical analysis of DNA

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20
Q

structure of DNA

A

double helical strcuture made of 2 single strands that wind round each other
one groove of helix is narrow and one is wide
strands are antiparallel
held together by hydrogen bonds
3 bonds between GC pairs, 2 between AT
where genomes need to unwind (start of transcription) there tends to be more AT

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21
Q

structure of nucleotide

A

purine/ pyrimidine base
pentose
2’ carbon position determines RNA/ DNA (OH in ribose sugar, H in deoxyribose sugar)
3’ carbon has hydroxyl group attached
5’ carbon has phosphate group attached
gives DNA and RNA negative charge

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22
Q

purines

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A

double nitrogenous

23
Q

pyrimidines

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A

single nitrogenous ring structure

24
Q

purines and pyrimidines

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A

attached to pentose sugar
A pairs with T- forms two H bonds
G pairs with C and forms 3 H bonds

25
nucleoside
sugar + base
26
nucleotide
sugar + base + phosphate
27
5' phosphate end
free phosphate group not involved in forming a bond with another nucleotide
28
3' hydroxyl end
free hydroxyl group the phosphate group at this end is involved in forming a bond
29
space filling model
bases stacked in planar arrangement horizontal running up through centre of DNA
30
B DNA
common type of DNA found in cells large major groove narrow minor groove major groove often recognised by DNA binding proteins- more edges of bases exposed for interaction some interact in minor groove
31
A DNA
similar to form adopted by dsRNA or RNA/ DNA hybrids more compact than B distance between bases is smaller (2.6 A) helix diameter larger
32
Z DNA
found in vitro in repeated DNA may form transiently in vivo during gene transcription (RNA synthesis) zig-zag DNA left handed narrow diameter stretched
33
structure of RNA
single stranded molecule very similar to single strand of DNA but contains U instead of T ribose sugar instead of deoxyribose
34
3 important types of RNA
mRNA rRNA tRNA
35
mRNA
- copied from DNA and used to make protein intermediate between DNA and protein
36
rRNA
ribosomal RNA functional RNA component to the ribosome translational machinery in cells
37
dATP
building blocks of DNA used in PCR deoxyadenosine triphosphate
38
tRNA
transfer RNA involved in process of translation tRNA bring amino acids to ribosomes during translation
39
structure of tRNA
'clover-leaf' shape single stranded but folds to form complex 3D structures base pairing occurs between different parts of the molecule to form stem and loop structures ( base pairing in stems to form the structure)
40
DNA replication
vital for passing on genetic information from cell to cell as cells divide and from generation to gen as organisms reproduce
41
watson and crick
1953 suggested a mechanism of how DNA could be replicated when they proposed the double helical structure of DNA
42
semi conservative method
double stranded DNA is unwound to produce 2 single strands (parent strands) and each parent strand is used to produce a daughter strand each new molecule has one og parent strand and one new daughter strand
43
meselson and stahl experiment
DNA extracted and centrifuged to equilibrium in CsCL density gradient grow bacteria in heavy 15N - og parent mol 2 strands heavy grow bacteria in normal 14N - first gen daughter molecules have one strand light one strand heavy continue to grow bacteria in normal 14N - second gen daughter mols have 2 helices light and 2 with one heavy and one light strand
44
requirements for polymerisation of the nucleic acid chain
1. dNTP's (dGTP, dATP, dCTP, dTTP) - triphosphate groups 2. a template (parent strand to copy) 3. a primer (another strand paired with the template to give a 3' end)
45
DNA polymerase
brings in a nucleotide triphosphate with a base complementary to the template DNA strand and phosphodiester bond is formed between the incoming nucleotide and the 3' hydroxyl end of he strand being extended with 2 of the phosphate groups being released
46
leading strand
made continuously primer extended by DNA polymerase from left to right primer orientated 5' to 3' and extended from 3' end
47
lagging strand
made discontinuously cannot be made in same direction as DNA being unwound need to wait until DNA is unwound before adding primer with the lagging strand being made in a series of fragments
48
dna rep primed by RNA
rna primer synthesised by primase dna polymerase III extends primer process repeated to form 'okazaki' fragments
49
rna primers removal
5'-3' exonucleases removes RNA removed by DNA polymerase I and Rnase H in E.coli and Pol I extends the DNA chain Nicks removed by DNA ligase
50
51
replication fork
the point at which the double stranded DNA is unwound by the helicase enzyme semi conservative model of replication predicts that replicating DNA would have this 'replication fork'
51
directional replication of DNA
strand that is made as the leading strand on one side of the origin of replication is made as the lagging strand on the other side of the origin
51
detection of fork movement using radioisotopes
grow e.coli in media without radioisotope grow breifly in low level of radioisotope 3H thymidine labels new DNA grow in higher level or radioisotope isolate DNA em grid detect label via photographic emulsion
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