nucleic acids part 1

Question 1

what are nucleic acids involved in ?

Answer 1

organisation , maintenance and regulation of cellular functions

Question 2

how is information stored in DNA ?

Answer 2

through the base pair sequence

Question 3

what are genes hereditary to

Answer 3

they are hereditary to chromosomes

Question 4

is the complexity of DNA directly proportional to its length ?

Answer 4

no , just because DNA is large in length this does not indicate complexity

Question 5

whats the 3 processes involved in genetic information transfer ?

Answer 5

DNA replication , transcription and translation

Question 6

what is the central dogma of molecular biology ?

Answer 6

DNA replication , transcription , RNA , translation , Protein

Question 7

how do reteroviruses store their genetic information ?

Answer 7

in RNA rather than DNA , this causes problems as the host cell doesn’t recognise RNA

Question 8

how does a reterovirus overcome host cell not recognising RNA ?

Answer 8

it uses an enzyme called reverse transcriptase to convert RNA to DNA

Question 9

whats an example of a reterovirus ?

Answer 9

HIV which becomes aids

Question 10

what are nucleic acids biopolymers of ?

Answer 10

nucleotides

Question 11

whats the difference between nuclotides and nucleosides ?

Answer 11

a nucleotide has a phosphodiester bond present while the nucleoside is just the sugar and base with no phosphodiester link instead OH on carbon 3

Question 12

what is the sugar phosphate DNA backbone ?

Answer 12

2-deoxy-D-ribose rings ( no OH carbon 2 ) that are joined by 3’ to 5’ phosphodiester linkages

Question 13

what holds the bases together and what does this form ?

Answer 13

hydrogen bonds that form between a purine and pyrimidine base and an antiparallel double helix forms

Question 14

what is the sugar phosphate RNA backbone ?

Answer 14

D-ribose rings that are linked by 3’ to 5’ phosphodiester linkages

Question 15

whats the difference structurally between DNA and RNA

Answer 15

RNA has a OH , hydroxyl, group on the 2’ position of the ribose ring.

Question 16

whats the 2 groups that the 4 bases are divided into?

Answer 16

purines and pyrimidines

Question 17

describe pyrimidines

Answer 17

this is a 6 membered ring with 2 nitrogens at carbon 1 and 3 position.

Question 18

bases that are pyrimidens ?

Answer 18

Cytosine and thymine

Question 19

describe purines

Answer 19

this is when a 5 membered ring and a 6 membered ring are fused together

Question 20

bases that are purines ?

Answer 20

guanine and adenine

Question 21

structurally what is different with uracil and what does this cause ?

Answer 21

it is missing a methyl group at C5 which makes the molecule smaller.

Question 22

what is the glycosidic linkage ?

Answer 22

this is when the nucleotide bases are connected to ribose sugar by c-n bond that replaces the N-H.

Question 23

are nucleosides found in DNA and RNA ?

Answer 23

no just DNA as it is missing the phosphate group.

Question 24

how do you name a nucleotide ?

Answer 24

based on the position of the phosphate

Question 25

what is an oligonucleotide ?

Answer 25

this is a short single strand of DNA that is made up of nucleotides ( contains phosphate)

Question 26

how come nucleotides can be describes as heterocyclic ?

Answer 26

This is due to them having nitrogen present in their rings

Question 27

what do the nitrogen atoms act as in the rings ?

Answer 27

nucleophiles

Question 28

equation for pKA ?

Answer 28

-logka

Question 29

what does Pka value measure ?

Answer 29

the position of equilibrium

Question 30

what does a large pkA value indicate ?

Answer 30

that the equilibrium lies to the left and that the base is strong

Question 31

what does a smaller Pka value indicate ?

Answer 31

that the equilibrium lies to the right

Question 32

Ka equation ?

Answer 32

[products] --------------- [reactants]

Question 33

is pyrrole a weak or strong base and why ?

Answer 33

it is a weak base as the lone pair of electrons aren't free to move as they are involved in pi bonding

Question 34

what is a nucleophile ?

Answer 34

this is a molecule that is negatively charged or contains lone pair of electrons , it is attracted to positive charged (electrophiles)

Question 35

what are many carcinogenic chemicals , nucleophilic or elctrophilic ?

Answer 35

electrophilic as they react with the nucleophilic nitrogen in the bases.

Question 36

what is tautomerisation ?

Answer 36

this is the transfer of a hydrogen atom from one place to another within the same molecule

Question 37

whats the 2 structures called before and after the hydrogen has been transferred

Answer 37

tautomers

Question 38

what are good examples of tautomerisation ?

Answer 38

nucleotide bases

Question 39

what occurs if small amounts of less stable tautomers of DNA occur ?

Answer 39

this can result in serious consequences in cell replication

Question 40

what is a hydrogen bond ?

Answer 40

An electrostatic attraction between a hydrogen atom and a lone pair of electrons

Question 41

what's normally the elements that are attracted to hydrogen and why

Answer 41

nitrogen or oxygen as they are highly electronegative

Question 42

what is an intramolecular interaction ?

Answer 42

within the same molecule

Question 43

what is an intermolecular interaction ?

Answer 43

between 2 different molecules

Question 44

what functional groups are classed as hydrogen bond donors ?

Answer 44

OH and NH

Question 45

what functional groups are classified as hydrogen bond acceptors

Answer 45

functional groups with lone pairs

Question 46

based on a molecule having angular structure or linear which is stronger ?

Answer 46

the linear

Question 47

when is the hydrogen described as being complementary ?

Answer 47

is the HBD and HBA line up correctly

Question 48

what causes a change in the hydrogen bonding ?

Answer 48

tautomerisation of the carbonyl group or amino groups and HBD become HBA and vice versa

Question 49

what can this lead to ?

Answer 49

incorrect base pairing which will alter the DNA sequence and could result in a mutation

Question 50

how is the error rate of DNA decreased ?

Answer 50

due to the presence of proof reading enzymes that remove tautomerisation base mismatches

Question 51

how do phosphate esters differ to organic esters ?

Answer 51

in phosphate esters it is possible to replace all 3 hydroxyl groups (oh) to alkoxy groups (OR)

Question 52

how does phosphodiester hydrolysis occur ?

Answer 52

in water with an acid or base catalyst

Question 53

are phosphate esters stable or not and what does this mean ?

Answer 53

they are relatively stable so the hydrolysis will require harsh condtions

Question 54

how is the hydrolysis of RNA and DNA different and why ?

Answer 54

RNA is less stable due to the presence of the OH group at 2' of the ribose ring.

Question 55

why does sugar base cleavage occur and what is produced ?

Answer 55

because the sugar base link ( glycosidic) is unstable to acid hydrolysis , especially the purines and abasic DNA is produced ( sugar separate from base)