DNA and RNA

Question 1

what is a Pyrimidine

Answer 1

nitrogen containing single ring compound (6 membered) that occurs in nucleic acids.

Question 2

How are nucleotides joined?

Answer 2

How are nucleotides joined?

Question 3

DNA and RNA are what?

Answer 3

long nucleic chains forms of nucleotides (polynucleotides)

Question 4

each strand of double helix is oreinated what?

Answer 4

in the opp direction

Question 5

describe the opp ends of the double helix

Answer 5

5’ end contains a free polar phosphate group
3’ end contains a free polar hydroxyl group OH

Question 6

where does the syntehsis of nucleic acid chain take place>

Answer 6

from 5’ to 3‘

Question 7

how does the dna grow

Answer 7

The ‘bottom’ of the nucleic acid (3’ end)’s OH group is ‘attacked from below’ by the PO4 linked to 5’ end of a free nucleotide, which then adds onto the chain -‘extended bottom end’

Question 8

is the backbone of the DNA HYDROPHILLIC

Answer 8

yes -sugar-phosphate backbone of DNA is polar

Question 9

Hydrostatic Interactions in DNA

Answer 9

polar backbone of DNA likes water, while the non-polar bases don’t. This creates a stable structure where the hydrophobic bases are tucked away inside the DNA molecule, held together by the pressure created by their aversion to water.

Question 10

a nucleic acid chain IS CALLED WHAT?

Answer 10

strand

Question 11

Nucleic acid structure

Answer 11

length of a nucleic acid chain is measured by the number of bases it contains.

In double-stranded nucleic acids, the bases are paired between the two strands, and the length is often expressed in base pairs

Question 12

Nucleic acid secondary structure:
DNA double helix

Answer 12

The two strands are “antiparallel“, i.e. one strand runs 5′ to 3′ while the other runs 3′ to 5′

Question 13

hydrogen bonding in DNA double helix

Answer 13

the purine or pyrimidine base attached to each deoxyribose sugar points inward towards the axis of the helix.

Each base pairs up with its complementary base on the opposite strand through hydrogen bonding, forming base pairs, also known as nucleotide pairs.

Question 14

RNA

Answer 14

tertiary structure is similar to DNA,

Single stranded but usually forms intra-molecular base pairs

Uracil instead of thymine

Question 15

what are the 3 forms of RNA

Answer 15

MRNA-found in the nucleus and transfers genetic information to the ribosome for protein synthesis

RRNA- found in the cytoplasm and important structural component of ribosomes

TRNA- . transfers AA’s to ribosome

Question 16

DNA replication?

Answer 16

-During nuclear division the two strands of the DNA double helix separate through the action of the enzyme DNA helicase

-Each DNA strand direct the synthesis of a complementary DNA strand through specific base pairing

-Resulting in two daughter DNA duplexes that are identical to the original parent molecule

Question 17

why is dna described as semi conservative

Answer 17

only one strand of each resultant daughter molecule is newly synthesized.

Question 18

DNA replication - requirements

Answer 18

Template strand of single-stranded DNA

‘Building blocks’ of DNA – nucleotides

Question 19

how do we unwind the DNA

Answer 19

Helicase unwinds DNA double helix so that the single DNA strands are available to be templates for synthesizing new DNA strands

Question 20

Describe DNA helicase

Answer 20

an ATP dependent catalytic enzyme

Question 21

what happesn when the dna has been unwinded?

Answer 21

The two unwound DNA strands then each serve asa template for DNA polymerase to make complementary DNA strands

-using the four deoxynucleoside triphosphates

Question 22

four deoxynucleoside triphosphates

Answer 22

(dATP, dCTP, dGTP, and dTTP).

Question 23

Direction of replication

Answer 23

New nucleotides are only added to the 3’ end of a growing strand

The replication is in a 5’ to 3’ direction

Forming bifurcated Y-shaped structures known as replication forks

Question 24

where is dna replication iniated?

Answer 24

ORIGINS OF REPLICATION

Question 25

what is the leading strand

Answer 25

When DNA is being replicated, one of the two strands serves as a template for continuous synthesis.

Question 26

the leading strand and dna polymerase

Answer 26

the DNA polymerase enzyme can move along this template strand in the 3’ to 5’ direction, adding nucleotides in the 5’ to 3’ direction. As a result, the new complementary strand is synthesized continuously in the same direction as the movement of the replication fork.

Question 27

what is the lagging strand?

Answer 27

the one that doesnt act as a template

Question 28

what happens to the lagging strand in dna replication?

Answer 28

replicated discontinuously.

This is because the DNA polymerase enzyme can only add nucleotides in the 5’ to 3’ direction. However, the lagging strand template is oriented in the 3’ to 5’ direction.

Question 29

how does the dna not get repliocated discounitsly?

Answer 29

lagging strand is synthesized in short, separate fragments known as Okazaki fragments. These fragments are later joined together by an enzyme called DNA ligase to form a continuous complementary strand.

Question 30

dna replication summarised easily?

Answer 30

during DNA replication, one strand is copied continuously from start to finish (leading strand), while the other strand is copied in short segments (Okazaki fragments) because of its opposite orientation

Question 31

Joining of Okazaki fragments

Answer 31

Fragments are joined by the enzyme DNA ligase.