nucleic acids

Question 1

what is the monomer of nucleic acids

Answer 1

nucleotides

Question 2

what do nucleic acids contain?

Answer 2

C, H, O, N, P

Question 3

How are nucleotides formed?

Answer 3

• contains phosphate group, pentose sugar (deoxyribose/ribose) and nitrogenous base
• forms phosphoester bond between carbon 5 of pentose sugar and phosphate group

Question 4

what are the purine bases?

Answer 4

adenine and guanine

Question 5

what are the pyrimidine bases?

Answer 5

thymine and cytosine

Question 6

how does polynucleotide form?

Answer 6

• forms via condensation reactions, releases water molecule
  phosphodiester bond forms between the hydroxyl group on carbon 3 of the pentose sugar of one nucleotide and the phosphate group on another nucleotide

Question 7

DNA structure

Answer 7

• double helix strand
• two polynucleotide chains held together by hydrogen bonds between complementary base pairs (adenine and thymine , cytosine and guanine)
• phosphodiester bonds form between each nucleotide
• polynucleotides form sugar phosphate backbone, consisting of a phosphate group, nitrogenous base and deoxyribose sugar
• strands are anti-parallel

Question 8

RNA structure

Answer 8

• contains ribose sugar
• contains bases = adenine, cytosine, guanine and uracil

Question 9

differences between DNA and RNA

Answer 9

• dna found in chromosomes in nucleus whereas RNA found in cytoplasm
• dna is a long molecule, rna is much shorter
• dna is a double strand, rna is a single strand
• dna contains thymine whereas rna swaps thymine for uracil

Question 10

how does dna replication occur?

Answer 10

• dna helicase breaks hydrogen bonds between base pairs, unzipping the dna and separating the strands
• original strand acts as a template
• free nucleotides match up with their complimentary base pair, forming hydrogen bonds between them
• dna polymerase forms phosphodiester bonds between nucleotides via condensation reactions
• dna consists of an original and new strand

Question 11

dna polymerase

Answer 11

• ## can only function in the 5 to 3 direction

Question 12

who discovered dna?

Answer 12

crick and watson

Question 13

what is semi-conservative replication?

Answer 13

each replicated dna molecule contains one original stand and one new strand

Question 14

why did Meselson and stahl use nitrogen

Answer 14

bases contain nitrogen, bacteria would use it to form new dna

Question 15

meselson and stahl’s method

Answer 15

• gen 0 only given nitrogen 15, therefore when replicating, dna only consists of dna 15. When centrifuged, one line low down as it is only one dna type and is dense
• gen 1 given n 14, when replicating it uses one original strand of n15 and one new strand of n14. When centrifuged, one line, same thickness, slightly higher due to being less dense than just n15
• gen 3 only make new dna out of n14, one n15 strand acts as a template but other strand is n14. when centrifuged, two thin lines, one higher and lower, two dna types, 50% of the dna

Question 16

why does dna polymerase move in opposite directions?

Answer 16

• dna strands are antiparallel
• dna polymerase is an enzyme with a specific shaped active site which can only bind to substrate with a complimentary shape
• can only bind to and add nucleotides to carbon 3 end of developing strand so works in 5 to 3 direction

Question 17

why does inhibitors have greater effect on cancer cells?

Answer 17

cancer cells replicate faster

Question 18

structure of dna related to its functions

Answer 18

double stranded - both strands act as template for semi-conservative replication
weak hydrogen bonds between base pairs - can be unzipped for replication
long molecule - store lots of genetic information
double helix - compact