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BIOL1024 Fundamentals of Biochemistry > DNA- the genetic material - structure > Flashcards

DNA- the genetic material - structure Flashcards

Structure Chardaff's rule DNA discovery BDNA and DNA melting (51 cards)

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1
Q

When was DNA discovered

A

1953 - James Watson, Francis Crick and Rosalind Franklin and Maurice Wilkins

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2
Q

What does DNA contain

A

Deoxyribose sugar
Phosphate
Organic bases

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3
Q

Organic bases family - Pyrimidines

A

single ringed nitrogenous

Thymine and Cytosine

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4
Q

Organic bases family - Purines

A

double ringed nitrogenous

Adenine and Guanine

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5
Q

DNA deoxyribose
Sugar attachments and alcohol
in Carbon 1, 3 and 5

A

carbon 1 - Base attaches to -OH
carbon 3 - (3’) secondary alcohol binds to phosphate
carbon 5 - (5’) primary alcohol binds to another phosphate

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6
Q

nulceoside

A

sugar + base

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7
Q

names of nucleoside

A

Adenosine
Thymidine
Guanosine
Cytidine

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8
Q

Nucleoside + phosphate

A

Deoxynucleoside triphosphate

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9
Q

Bonds between sugar and base

A

Glycosidic bond

N-linked by condensation reaction

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10
Q

Bonds between phosphate and sugar (3’ and 5’ -OH)

A

Phosphodiester backbone

By condensation reaction

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11
Q

Chardaff’s rule

A

No. A= No. T and No. C= No. G

Purines = Pyrimidines

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12
Q

Method of Chardaff’s rule

A

Break Phosphodiester bond and purify DNA using acid
Separated by paper chromatography
use UV spectrophotometry to identify individual bases and its proportions

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13
Q

Rosalind Franklin and Maurice Wilkins

A

X-ray diffraction patterns on DNA fibres

makes fundamental repeating distances in DNA

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14
Q

Method for X-ray crystallography

A

Purify DNA and change humidity = different forms of DNA
fixed piece of DNA on support, sealed in front of film and behind the camera
bombarded DNA with x-ray = x-ray diffraction - (e-) which scatter

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15
Q

Increasing humidity to 92%

A

forming BDNA

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16
Q

James Watson and Francis Crick

A

1953

discovered the DNA model with the double helix

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17
Q

properties of bases

A

hydrophobic and stack on top in the core

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18
Q

distance of bases

A

optimal separation for VdW interaction

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19
Q

strands direction

A

antiparallel one from 5’ to 3’ and other 3’ to 5’

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20
Q

strands of BDNA and its direction

A

double stranded and goes in right handed direction

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21
Q

Distance between base pairs in BDNA

22
Q

distance per turn of BDNA

Study These Flashcards
A

3.4nm per turn

10 bp per turn

23
Q

Meaning of bp

24
Q

Right handed helix - rotation direction

Study These Flashcards
A

DNA curl in clockwise direction

25
diameter of BDNA
around 2nm
26
why is slightly off set - not symmetrical
has major and minor groove
27
groove
gaps between the sides (backbone)
28
A-DNA direction
right handed
29
Cause of A-DNA
Decrease in humidity therefore was dehydrated
30
structures of A-DNA
wider, bases tilted and off set from axis
31
Z-DNA direction
Left handed - anitclockwise
32
Cause of Z-DNA
GC containing sequence at high salt concentration
33
Max DNA absorbance
260nm - light wave
34
Comparison of single and double stranded DNA in absorbancy
Single stranded DNA has higher absorbance
35
Tm (degrees celcius)
mid point of transition
36
Affect of GC rich DNA
melt at higher temperature due to 3 hydrogen bonds
37
Affect of longer DNA fragments
require higher temperature to melt
38
Affect of higher salt concentration
requires higher temperature as positive ions neutralise negative phosphate backbone
39
hypochromic effect
Limited absorbance until double strand separate
40
Hyperchromisity occur
at 260nm form single stranded
41
Proteins in chromatin
Histones , 5 proteins
42
name of 5 histones
H1, H2A, H2B, H3, H4
43
Histonecore
2 copies of each H2A, H2B, H3, H4 forming octametric - disk like structure
44
Nucleosome
DNA wraps around histones 1.6 times
45
condensed nucleosomes
arranged in 'bead on string', condensed to form higher-order structures and compact DNA
46
Role of H1 histones
linker histones | changes conformation of DNA as it leaves nucleosome - compact DNA - create kink
47
What H1 histones do
bind to nucleosome, contacts protein and DNA, able to change conformation of DNA as it leaves
48
histones property
Rich in basic therefore positively charged
49
number of base pairs per cell
6,000,000,000 around 2m
50
number of cells in body
10 to power of 14
51
DNA per cell
0.6pg

BIOL1024 Fundamentals of Biochemistry (25 decks)

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