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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

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

A

0.34nm

22
Q

distance per turn of BDNA

A

3.4nm per turn

10 bp per turn

23
Q

Meaning of bp

A

base pairing

24
Q

Right handed helix - rotation direction

A

DNA curl in clockwise direction

25
Q

diameter of BDNA

A

around 2nm

26
Q

why is slightly off set - not symmetrical

A

has major and minor groove

27
Q

groove

A

gaps between the sides (backbone)

28
Q

A-DNA direction

A

right handed

29
Q

Cause of A-DNA

A

Decrease in humidity therefore was dehydrated

30
Q

structures of A-DNA

A

wider, bases tilted and off set from axis

31
Q

Z-DNA direction

A

Left handed - anitclockwise

32
Q

Cause of Z-DNA

A

GC containing sequence at high salt concentration

33
Q

Max DNA absorbance

A

260nm - light wave

34
Q

Comparison of single and double stranded DNA in absorbancy

A

Single stranded DNA has higher absorbance

35
Q

Tm (degrees celcius)

A

mid point of transition

36
Q

Affect of GC rich DNA

A

melt at higher temperature due to 3 hydrogen bonds

37
Q

Affect of longer DNA fragments

A

require higher temperature to melt

38
Q

Affect of higher salt concentration

A

requires higher temperature as positive ions neutralise negative phosphate backbone

39
Q

hypochromic effect

A

Limited absorbance until double strand separate

40
Q

Hyperchromisity occur

A

at 260nm form single stranded

41
Q

Proteins in chromatin

A

Histones , 5 proteins

42
Q

name of 5 histones

A

H1, H2A, H2B, H3, H4

43
Q

Histonecore

A

2 copies of each H2A, H2B, H3, H4 forming octametric - disk like structure

44
Q

Nucleosome

A

DNA wraps around histones 1.6 times

45
Q

condensed nucleosomes

A

arranged in ‘bead on string’, condensed to form higher-order structures and compact DNA

46
Q

Role of H1 histones

A

linker histones

changes conformation of DNA as it leaves nucleosome - compact DNA - create kink

47
Q

What H1 histones do

A

bind to nucleosome, contacts protein and DNA, able to change conformation of DNA as it leaves

48
Q

histones property

A

Rich in basic therefore positively charged

49
Q

number of base pairs per cell

A

6,000,000,000 around 2m

50
Q

number of cells in body

A

10 to power of 14

51
Q

DNA per cell

A

0.6pg

BIOL1024 Fundamentals of Biochemistry (25 decks)

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