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Biol251 > DNA > Flashcards

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
Q

Bacteriophage replication

A

For the virus to replicate, it must use host cells; so the virus must be injecting its genetic material into a host.

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26
Q

HERSHEY & CHASE purpose

A

analyzed what a virus was injecting into host cells for the sake of replication (what is the genetic material)?

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27
Q

Transfection experiments

A

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

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28
Q

Transfection definition

A

DNA in the environment can be uptaken by other bacteria

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29
Q

Proof of DNA being genetic material in eukaryotes: distribution

A

DNA is only found where primary genetic function is known to occur; protein is ubiquitous

DNA content corresponds with ploidy level

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30
Q

Proof of DNA being genetic material in eukaryotes: mutations

A

mutagenesis corresponds to absorption spectrum of DNA, not protein

the more UV light DNA absorbs, the more mutations

31
Q

Best nm for absorption of UV by DNA

A

most absorption at 260 nm

32
Q

QB bacteriophage

A

RNA is genetic material

has RNA replicase

33
Q

RNA replicase

A

Allows creation of more RNA from RNA template

RNA to RNA

34
Q

Retrovirus

A

RNA is genetic material

Reverse transcriptase used to make DNA copy of RNA genome

Inserts this DNA copy into your genome

35
Q

Reverse transcriptase

A

RNA-dependent DNA polymerase

Usually, from DNA, you make RNA

Now you use RNA to make DNA

RNA to DNA

36
Q

Which RNA virus has which enzyme?

A

Retrovirus: Reverse transcriptase
QB bacteriophage: RNA replicase

37
Q

Nucleic acid

A

Nucleic acids are polymers

Their monomers are nucleotides

DNA and RNA are nucleic acids

38
Q

Nucleotides

A

the monomers of nucleic acids

made of 3 components:
sugar + base + phosphate group

39
Q

dNMP

A

nucleoside monophosphates

another word for nucleotides

nucleoside + 1 phosphate group

39
Q

Nucleoside

A

sugar + base; an abbreviation of a nucleotide’s components, minus the phosphate

40
Q

dNTP

A

nucleoside triphosphates

precursor molecule for DNA synthesis

extra phosphate groups are used as a source of energy for the synthesis process

41
Q

Two major types of nucleic acid & their difference

A

DNA and RNA

difference in sugar base: one is missing an oxygen in their hydroxyl group

42
Q

Purine

A

A, G
larger, it has 2 rings

43
Q

Pyrimidine

A

C, T, U
narrower, it has 1 ring
DNA has a T, RNA has a U

44
Q

What are incoming monomers to DNA molecules?

A

nucleoside triphosphate

45
Q

Where are incoming monomers added to DNA molecules? How?

A

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
Q

sugar-phosphate backbone

A

the hydroxyls of the sugars, and the phosphate groups attached to the sugars, are what chain nucleotides together

47
Q

Key features of Watson and Crick’s double-helix model

A

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
Q

Why is the sugar-phosphate backbone on the outside?

A

Hydrophilic environment surrounds DNA

Phosphate is charged, so the backbone is hydrophilic itself

This repels unwanted interactions from the bases

49
Q

Purpose of grooves in helix structure

A

Allows nucleotides to be partially exposed

Binding sites for various proteins are within the grooves

50
Q

Minor groove

A

Groove where the two parts of the backbone are close together

51
Q

Major groove

A

Groove where the two parts of the backbone are far apart

52
Q

5’ end

A

phosphate group

53
Q

3’ end

A

hydroxyl group

54
Q

Antiparallel

A

nucleic acids have “ends”

if one end is 3’, it is across from a 5’ end

Allows for complementary base pairing

55
Q

Complementary base pairing

A

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
Q

How do base pairs bond & significance of this

A

H-bonds

More H-bonds, more stable helix

57
Q

semi-conservative model of DNA replication

A

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
Q

How is RNA different from DNA?

A

in RNA, sugar is oxygenated

uses uracil in place of thymine

RNA is single strand

59
Q

snRNA

A

processes mRNAs for post-transcriptional splicing

60
Q

Use of miRNA, siRNA, lncRNA

A

involved in gene regulation

61
Q

Telomerase function

A

Extends the DNA ends (telomeres) so that they do not devour themselves in DNA replication

62
Q

How does telomerase work

A

There is an RNA sequence inside of it which functions as RNA primer

63
Q

Melting temperature (tm)

A

represents point at which 50% of strands are melted

can be used to estimate base composition of DNA

64
Q

hyperchromic shift

A

UV absorbance increases as DNA is denatured

when melt DNA, the helix dissociates, and the exposed bases are able to absorb UV

65
Q

Melting profile

A

absorption of UV plotted against temp

increases with increasing temp

66
Q

tm relation to base composition

A

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
Q

Renaturation

A

DNA reforms h-bonds after being denatured by heat

68
Q

What are 3 things DNA can renature with?

A

The original DNA fragments

DNA from different organisms

between DNA and RNA strands

69
Q

Probes

A

nucleic acid like DNA or RNA

labeled and can be detected

Used to identify complementary sequences in denatured DNA

70
Q

Molecular hybridization

A

DNA renaturation rejoins whatever’s closest and complementary enough; perfect complementation not needed

DNA can be manipulated to rejoin with whatever

71
Q

FISH stands for what

A

fluorescent in situ hybridization

72
Q

FISH concept

A

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
Q

Electrophoresis

A

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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