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Flashcards in DNA Structure Deck (25)
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1

Nucleosides

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

2

Nucleotide

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

3

if the pentose is ribose, the nucleic acid is

RNA

4

if the pentose is deoxyribose, the nucleic acid is

DNA

5

a molecule is aromatic if:

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

6

key features of the DNA double helix:

- 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)

7

A and T pairing is via _____;
C and G pairing is via

2 hydrogren bonds; 3 hydrogen bonds

the C & G pairing have a stronger interaction

8

Chargaff's rules:

%A = %T
%G = %C

9

B DNA vs Z DNA

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

10

Denaturation can be caused by

heat
alkaline pH
formaldehyde
urea

11

Histones

small pack of proteins that contain DNA

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

12

Heterochromatin

dark, dense and silent

13

Euchromatin

light, uncondensed and expressed

14

telomere

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.

15

In eukaryotes, DNA is would around ______ to form nucleosomes

histone proteins (H2A,H2B,H3 and H4)

16

Centromeres

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

Replisome aka replication complex

a set of specialized proteins that assist the DNA polymerases

18

Single stranded DNA binding proteins

proteins that keep the unbound strands from reannealing or being degraded

19

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

Supercoiling; DNA topoisomerase II (DNA gyrase)

20

DNA polymerase III

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

21

leading strand

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

22

lagging strand

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

23

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

DNA polymerase I; RNase H (eukaryotes)

24

DNA ligase

can fuse the DNA strands together to create one complete molecule

closes the gaps between okazaki fragments

lack the proofreading ability

25

Sliding clamp

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