DNA Structure Flashcards

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1
Q

Nucleosides

A

a 5 carbon sugar (pentose) bound to a nitrogenous base and are formed by covalently linking the base to C - 1’ of the sugar

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2
Q

Nucleotide

A

when one of more phosphate groups are attached to C - 5’ of a nucleoside.

high energy compounds because of the energy associated with the repulsion between closely associated negative charges on the phosphate groups

building blocks of DNA

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3
Q

if the pentose is ribose, the nucleic acid is

A

RNA

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4
Q

if the pentose is deoxyribose, the nucleic acid is

A

DNA

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5
Q

a molecule is aromatic if:

A

the compound is cyclic
the compound is planar
the compound is conjugated
the compound has 4n+2

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6
Q

key features of the DNA double helix:

A
  • the two strands of DNA are antiparallel; the strands are orientated in opposite directions.
  • the sugar phosphate backbone is on the outside of the helix with the nitrogenous bases on the inside
  • complementary base pairing
  • the amount of A equals the amount of T and the amount of G equals the amount of C (the total of purines will always be equal to the total of pyrimidines overall) (Chargaff’s rules)
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7
Q

A and T pairing is via _____;

C and G pairing is via

A

2 hydrogren bonds; 3 hydrogen bonds

the C & G pairing have a stronger interaction

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8
Q

Chargaff’s rules:

A
%A = %T
%G = %C
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9
Q

B DNA vs Z DNA

A

Z DNA is way too unstable therefore too difficult to be used in research; has a high G & C content and high Salt concentration; left handed DNA

B DNA has major and minor grooves; right handed DNA

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10
Q

Denaturation can be caused by

A

heat
alkaline pH
formaldehyde
urea

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11
Q

Histones

A

small pack of proteins that contain DNA

Example of a nucleoprotein (acid soluble that tend to stimulate processes such as transcription)

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12
Q

Heterochromatin

A

dark, dense and silent

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13
Q

Euchromatin

A

light, uncondensed and expressed

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14
Q

telomere

A

ends of chromosomes
contain high GC content to precent unraveling of the DNA

During replication, telomeres are slightly shortened, although this can be (partially) reversed by the enzyme telomerase.

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15
Q

In eukaryotes, DNA is would around ______ to form nucleosomes

A

histone proteins (H2A,H2B,H3 and H4)

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16
Q

Centromeres

A

located in the middle of chromosomes and hold sister chromatids together until they are separated during anaphase in mitosis.

Contain high GC content to maintain a strong bond between chromatids

17
Q

Replisome aka replication complex

A

a set of specialized proteins that assist the DNA polymerases

18
Q

Single stranded DNA binding proteins

A

proteins that keep the unbound strands from reannealing or being degraded

19
Q

_______ causes torsional strain on the DNA molecule, which can be released by ______, which creates nicks in the DNA molecule

A

Supercoiling; DNA topoisomerase II (DNA gyrase)

20
Q

DNA polymerase III

A

can synthesize a new stand of DNA; they read the template DNA 3’ to 5’ and synthesize the new strand 5’ to 3’

21
Q

leading strand

A

requires only one primer and can then be synthesized continuously in its entirety

22
Q

lagging strand

A

requires many primer and is synthesized in discrete sections called Okazaki fragments

23
Q

RNA primers can be removed by ____ or ____, and filled in with DNA by DNA polymerase I

A

DNA polymerase I; RNase H (eukaryotes)

24
Q

DNA ligase

A

can fuse the DNA strands together to create one complete molecule

closes the gaps between okazaki fragments

lack the proofreading ability

25
Q

Sliding clamp

A

helps to strengthen the interaction between DNA polymerases and the template strand