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DNA Flashcards

1
Q

Traits of a genetic material

A

replication
storage of information
expression of information
variation by mutation

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2
Q

Tetranucleotide hypothesis

A

DNA is made of linked, repeating tetramers of nucleotides

all 4 nucleotides present in equal amounts

DNA was therefore uniform and simple

Incorrect

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3
Q

Who discovered DNA and how

A

Miescher

He found nucleic acids, derived from the nucleus of a WBC, which he called “nuclein”

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4
Q

Nuclein

A

nucleic acids, derived from the nucleus of a WBC; Miescher’s discovery of DNA

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5
Q

Miescher’s assumptions and discoveries about nuclein

A

ASSUMPTIONS:
He believed it was novel due to its resistance to protease digestion

DISCOVERIES:
He found it was in all nuclei

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6
Q

Why was protein thought to carry genetic information, as opposed to DNA?

A

DNA seemed to lack chemical diversity

early tetranucleotide hypothesis stated nucleotides were in short repetitive sequences, so did not seem to encode anything

protein has structural diversity

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7
Q

GRIFFITH Experiment design

A

two strains of bacteria: one virulent, one avirulent

heated to death some of the bacteria

introduced bacteria (both alive and dead) into mice in varying combinations

1 avirulent, 1 virulent, 1 dead virulent, 1 dead virulent + living avirulent

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8
Q

GRIFFITH results

A

IIR, living
mouse lived

IIIS, living
mouse died

dead IIIS
mouse lived

dead IIIS and IIR
mouse died

when the dead virulent and living avirulent strain were mixed, the mouse died

living IIIS was recovered from the dead mouse

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9
Q

GRIFFITH conclusions

A

Something in the dead IIIS must be making the IIR virulent.

He called this the transforming principle.

a transforming principle exists in bacteria which allow them to pass traits to other bacteria

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10
Q

Transforming principle

A

Something taken up from the environment by one bacterium, which was shed by another, and allows it to transform or change to be like the principle’s source

allows the passage of traits to other bacteria

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11
Q

Griffith’s virulent strain

A

S FORM (smooth)

encapsulated
look smooth due to capsule

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12
Q

Griffith’s avirulent strain

A

R FORM (ROUGH)

no capsule
look rough

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13
Q

Serotype

A

refers to the antigens on the surface of the bacterium

each elicits a different immune response

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14
Q

Serotypes in Griffith’s experiment

A

In his experiments, Griffith used these two serotypes:

IIR, avirulent

IIIS, virulent

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15
Q

Why is one strain virulent and the other avirulent?

A

The difference in virulence depends on the presence of a glycocalyx.

The glycocalyx prevents engulfment of the bacteria, making them virulent.

They multiply and cause pneumonia.

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16
Q

IIR

A

avirulent
rough, no capsule

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17
Q

IIIS

A

virulent
smooth, encapsulted

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18
Q

AVERY Experiment design

A

heat-killed IIIS were broken up using detergent

extract of cellular contents was made

TWO DIFFERENT EXTRACTS:
1. protein was removed from extract using protease
2. DNA was removed using enzyme

IIR exposed to extracts to see if they would transform

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19
Q

AVERY results

A

for the extract with no DNA, no changes occurred in the IIR cells

for the extract with no protein, some IIR cells became IIIS

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20
Q

AVERY conclusions

A

Once DNA was removed from the filtrate no conversion occurred; so DNA is the transforming principle

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21
Q

HERSHEY & CHASE experiment design

A

The atoms unique to DNA and protein were labeled in two different groups of viruses using radioactive isotopes.

DNA: P
Protein: S

The labeled phages were allowed to infect bacteria

Cultures blended and centrifuged to produce pellets

shells of phages were separated out with supernatant

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22
Q

HERSHEY & CHASE results

A

Which material is associated with the pellets? That material is what was injected into the cell.

Radioactive phosphorus — DNA was the pellets

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23
Q

HERSHEY & CHASE conclusion

A

DNA is the genetic material

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24
Q

Bacteriophage structure

A

Phages have a protein capsid containing phage DNA. That’s all! Only protein and DNA.

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25
Bacteriophage replication
For the virus to replicate, it must use host cells; so the virus must be injecting its genetic material into a host.
26
HERSHEY & CHASE purpose
analyzed what a virus was injecting into host cells for the sake of replication (what is the genetic material)?
27
Transfection experiments
Lysozyme was used to destroy the E. coli cell wall Purified phage DNA (no proteins) was exposed to the bacteria no cell wall = easier uptake of DNA new phages were produced DNA alone contains all necessary information for the production of phages
28
Transfection definition
DNA in the environment can be uptaken by other bacteria
29
Proof of DNA being genetic material in eukaryotes: distribution
DNA is only found where primary genetic function is known to occur; protein is ubiquitous DNA content corresponds with ploidy level
30
Proof of DNA being genetic material in eukaryotes: mutations
mutagenesis corresponds to absorption spectrum of DNA, not protein the more UV light DNA absorbs, the more mutations
31
Best nm for absorption of UV by DNA
most absorption at 260 nm
32
QB bacteriophage
RNA is genetic material has RNA replicase
33
RNA replicase
Allows creation of more RNA from RNA template RNA to RNA
34
Retrovirus
RNA is genetic material Reverse transcriptase used to make DNA copy of RNA genome Inserts this DNA copy into your genome
35
Reverse transcriptase
RNA-dependent DNA polymerase Usually, from DNA, you make RNA Now you use RNA to make DNA RNA to DNA
36
Which RNA virus has which enzyme?
Retrovirus: Reverse transcriptase QB bacteriophage: RNA replicase
37
Nucleic acid
Nucleic acids are polymers Their monomers are nucleotides DNA and RNA are nucleic acids
38
Nucleotides
the monomers of nucleic acids made of 3 components: sugar + base + phosphate group
39
dNMP
nucleoside monophosphates another word for nucleotides nucleoside + 1 phosphate group
39
Nucleoside
sugar + base; an abbreviation of a nucleotide's components, minus the phosphate
40
dNTP
nucleoside triphosphates precursor molecule for DNA synthesis extra phosphate groups are used as a source of energy for the synthesis process
41
Two major types of nucleic acid & their difference
DNA and RNA difference in sugar base: one is missing an oxygen in their hydroxyl group
42
Purine
A, G larger, it has 2 rings
43
Pyrimidine
C, T, U narrower, it has 1 ring DNA has a T, RNA has a U
44
What are incoming monomers to DNA molecules?
nucleoside triphosphate
45
Where are incoming monomers added to DNA molecules? How?
the 3' hydroxyl group nucleoside triphosphate incoming One phosphate is linked to the hydroxyl group two phosphates are hydrolysed breaking bonds provides energy for the exergonic DNA synthesis
46
sugar-phosphate backbone
the hydroxyls of the sugars, and the phosphate groups attached to the sugars, are what chain nucleotides together
47
Key features of Watson and Crick's double-helix model
2 polynucleotide chains aligned chains wrapped around an axis sugar-phosphate backbone is on outside base pairs are "stacked" grooves exist in the helix diameter is unchanging
48
Why is the sugar-phosphate backbone on the outside?
Hydrophilic environment surrounds DNA Phosphate is charged, so the backbone is hydrophilic itself This repels unwanted interactions from the bases
49
Purpose of grooves in helix structure
Allows nucleotides to be partially exposed Binding sites for various proteins are within the grooves
50
Minor groove
Groove where the two parts of the backbone are close together
51
Major groove
Groove where the two parts of the backbone are far apart
52
5' end
phosphate group
53
3' end
hydroxyl group
54
Antiparallel
nucleic acids have "ends" if one end is 3', it is across from a 5' end Allows for complementary base pairing
55
Complementary base pairing
A & T G & C purines and pyrimidines ONLY, otherwise diameter of DNA will change A&C and G&T don't bond because those couplings don't provide maximum number of H-bonds
56
How do base pairs bond & significance of this
H-bonds More H-bonds, more stable helix
57
semi-conservative model of DNA replication
helix unzipped Single strands have a new daughter strand synthesized by following the base pairs of the original strands The original strands are conserved original-daughter helix created
58
How is RNA different from DNA?
in RNA, sugar is oxygenated uses uracil in place of thymine RNA is single strand
59
snRNA
processes mRNAs for post-transcriptional splicing
60
Use of miRNA, siRNA, lncRNA
involved in gene regulation
61
Telomerase function
Extends the DNA ends (telomeres) so that they do not devour themselves in DNA replication
62
How does telomerase work
There is an RNA sequence inside of it which functions as RNA primer
63
Melting temperature (tm)
represents point at which 50% of strands are melted can be used to estimate base composition of DNA
64
hyperchromic shift
UV absorbance increases as DNA is denatured when melt DNA, the helix dissociates, and the exposed bases are able to absorb UV
65
Melting profile
absorption of UV plotted against temp increases with increasing temp
66
tm relation to base composition
G-C has more H-bonds than A-T H-bonds absorb energy when broken DNA rich in G-C = higher temp needed to melt
67
Renaturation
DNA reforms h-bonds after being denatured by heat
68
What are 3 things DNA can renature with?
The original DNA fragments DNA from different organisms between DNA and RNA strands
69
Probes
nucleic acid like DNA or RNA labeled and can be detected Used to identify complementary sequences in denatured DNA
70
Molecular hybridization
DNA renaturation rejoins whatever's closest and complementary enough; perfect complementation not needed DNA can be manipulated to rejoin with whatever
71
FISH stands for what
fluorescent in situ hybridization
72
FISH concept
mitotic cells are fixed to slides and subjected to hybridization condition fluorescent ssDNA or RNA is added to detect similar sequences The added nucleic acids serve as a probe, hybridize only with areas that have sufficient complementarity added nucleic acids will fluoresce under a microscope, allowing detection
73
Electrophoresis
Separates DNA and RNA fragments by size in an electric field DNA and RNA are negative, go towards a positive cathode small fragments travel faster than large ones

Biol251 (8 decks)

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