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Intro to Molecular Biology > DNA structure and function > Flashcards

DNA structure and function Flashcards

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1
Q

Properties of DNA

A
  • Carries the information required to build proteins
  • Can be replicated so that an exact copy is passed to the next generation
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2
Q

Proteins vs DNA differences

A

PROTEINS
- The arrangement of was changes the structure of the protein
- The function of protein is dependent on its structure

DNA
- The arrangement of nucleotides does NOT change the structure of the molecule
- The information encoded by DNA is independent of its structure

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3
Q

basic features of DNA

A
  • DNA is a polymer of 4 different nucleotides (A, C, G, T)
  • The order of the nucleotides determines the information encoded by DNA
  • 2 complementary strands running in opposite directions
  • Complimentary nature allows replication
  • sugar-phosphate backbone
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4
Q

The sugar phosphate backbone of DNA

A
  • Sugar in DNA is a pentose (5-C) called ribose
  • Ribose can either be liner or a ring structure
  • in nucleic acids, ribose occurs in it’s ring form
  • The ring has 4Cs and includes one oxygen molecule
  • The 5th carbon is not not part of the ring, it sticks out of the molecule.
  • Each molecule is numbered from 1’ to 5’
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5
Q

draw ribose and deoxyribose

A

…..

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6
Q

what is phosphate ?

A

A molecule consisting of one atom of phosphorus and 4 atoms of oxygen

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7
Q

what can phosphate form bonds with ?

A

It can form ester bonds with the OH groups on the 5’and 3’ carbons of ribose or deoxyribose producing a diester bond. Resulting in altering sugar and phosphate subunits.

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8
Q

Directionality of DNA

A
  • 5’ end has a phosphate group bound to 5’ carbon
  • The 3’ end has an OH on the 3 ‘ carbon and does not have a phosphate group attached
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9
Q

what is a diester bond ?

A

ester groups are connected through a shared oxygen atom.

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10
Q

Properties of Pyrimidine bases (C,T,U)

A
  • They have an aromatic ring structure
  • Pyrimidine is composed of more that one atom (carbon+nitrogen atoms = heterocyclic
  • Pyrimidines are known as diazenes
  • ENE = 6 MEMEBER RING
  • DIAZ= 2 CARBONS REPLCED BY NITROGEN
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11
Q

Pyramidine bases found in DNA or RNA

A
  • They all share a common 4 carbon + 2 nitrogen ring structure
  • Uracil has the simplest structure
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12
Q

how to make thymine and cytosine from uracil ?

A
  • Addition of methyl group to make thymine
  • Addition of an amine group to make cytosine
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13
Q

What kind of ring do purines have ?

A

They contain a pyrimidine ring but bound to a second kind of ring structure called : IMIDAZOLE.
Thus, purines have a DOUBLE RING STRUCTURE consisting of a pyrimidine bound to an imidazole

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14
Q

what is an IMIDAZOLE ?

A

A diazole: a 5 member ring containing 2 nitrogens

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15
Q

PURINES found in DNA and RNA

A
  • they share a common double ring structure
  • both rings have an additional amine group, their location differs in adenine and guanine
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16
Q

what is the same of the bond linking a base and a sugar ? and what does it mean ?

A

N - glycosidic bond, which means a nitrogen atom of the base is bound to the sugar

17
Q

what is a nucleoside ?

A

a base bound to a sugar

18
Q

what is a nucleotide ?

A
  • building blocks of DNA
  • a nucleoside phospahte
19
Q

each nucleotide consists of 3 elements:​

A
  1. A nitrogenous base
  2. (A,T,C,G)​
  3. Deoxyribose​
  4. Phosphate​
20
Q

What is DNA synthesised from ?

A

Deoxy nucleoside triphosphate (dNTPs)

21
Q

what is triphosphate (e.g. dNTPs) ?

A
  • stores a lot of energy
  • hydrolysis of its bond provides energy for DNA synthesis.
22
Q

Given that purines and pyrimidines have very different sizes, how is this possible?​

A

one purine and one pyrimidine always bind together​

e.g. A-T base pair is exactly equal to the size of a G-C base pair​

23
Q

how many H-bonds between A and T ?

A

2H bonds

24
Q

how many H-bonds between G and C ?

A

3H bonds (help together more strongly)

25
Q

how much nm are adjacent bases separated by ?

A

0.34nm

26
Q

How many bases per helix turn ?

A

10 bases

27
Q

how many nm does helix replicate ?

A

3.4nm

28
Q

what is the diameter of the helix ?

A

2nm

29
Q

what are the 2 grooves on the surface of the helix ?

A

Major and Minor

30
Q

which groove do DNA binding proteins bind to and why ?

A

the major groove because there is more space

31
Q

are bases hydrophobic or hydrophilic ?

A

hydrophobic

32
Q

What is melting ?

A

When Anna strands separate for replication or transcription.
To do this H bonds must be broken

33
Q

DNA melting temperature ??

A

92 - 95C

34
Q

How do strands spontaneously re-associate ?

A

by lowering the temperature

35
Q

which one is less stable between DNA and RNA?

A

RNA is less stable than DNA

35
Q
A

Intro to Molecular Biology (1 decks)

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