nucleic acid part3

Question 1

what enzyme does DNA replication require ?

Answer 1

DNA polymerase , which synthesises a new daughter strand of DNA from the parental DNA strand.

Question 2

explain how DNA replication occurs ?

Answer 2

the DNA double helix is unzipped and this exposes the base pairs as the hydrogen bonds are no longer there. This requires a class of enzymes called type IIA topoisomerases - some of which are called DNA gyrases. Then a replication fork is produced. At the replication fork new nucleotides bases are added to the exposed bases on the unzipped parental DNA strand. DNA polymerase works in a 5’ to 3’ direction which results in the daughter strand forming the leading strand as it can continually grow. However , a lagging strand will form as the growth is fragmented , due to DNA polymerase only working in a 5’ to 3’ direction. However by the use of DNA primers which attach to the 3’ to 5’ parent strand ,replication can occur but it is in ozaki fragments. The ozaki fragments are covalently linked by enzyme DNA ligase. The primers then dissociate.

Question 3

what prevents the replication errors occurring in the base pairs staying ?

Answer 3

the body has proof reading functions such as DNA polymerase I and III and enzymes to prevent these.

Question 4

what is transcription and where does it occur ?

Answer 4

this is the synthesis of RNA from DNA , it occurs in the cells nucleus

Question 5

what is the blueprint for transcription ?

Answer 5

DNA bases

Question 6

what occurs to the double helix of DNA during transcription ?

Answer 6

it unwinds to form a bubble so that the bases are exposed on the 2 strands

Question 7

whats the base that replaces thymine for RNA ?

Answer 7

uracil

Question 8

what enzyme is required so that the new RNA nucleotides can be added ?

Answer 8

RNA polymerase

Question 9

what are the nucleotide monomers in RNA synthesis ?

Answer 9

nucleotide triphosphates ( NTP’s)

adenosine triphosphate
guanine triphosphate
cytosine triphosphate
uridine triphosphate

Question 10

what is released as the new nucleotide base pair is added to the growing RNA chain ?

Answer 10

a pyrophosphate { P207} 4-

Question 11

what is formed between the newly added NTP and the 3’- OH group of the growing RNA chain.

Answer 11

a phosphodiester linkage

Question 12

The 3’ to 5’ strand is sometimes referred to as ?

Answer 12

the antisense strand

Question 13

what is the 5’ to 3’ strand referred to as?

Answer 13

the sense strand

Question 14

are both strands of DNA replicated ?

Answer 14

no just one

Question 15

where does translation occur ?

Answer 15

in the ribosomes ( rRNA)

Question 16

what occurs at the ribosomes ?

Answer 16

this is where the peptides and proteins are synthesised.

Question 17

what is 3 nucleotides in mRNA called ?

Answer 17

a codon

Question 18

what binds to the codon and why ?

Answer 18

binds to tRNA which carries a specific amino acid which is covalently bound

Question 19

what can a single strand of tRNA be folded into ?

Answer 19

a clover leaf secondary structure with 3 loops

Question 20

what occurs during RNA self splicing ?

Answer 20

the junk bases are removed ( introns ) and the coding regions ( exons ) are joined together by an external catalyst