DNA & RNA

Question 1

3 components of DNA/RNA

Answer 1

1. nitrogenous base
2. ribose/deoxyribose
3. at least 1 P group

Question 2

nucleoside

Answer 2

nitrogenous base covalently linked to a 5-carbon sugar

Question 3

nucleotide

Answer 3

nucleoside + P group

Question 4

nucleoside triphosphates

Answer 4

ATP (adenosine triphosphate)

CTP

TTP

GTP

Question 5

what happens when ATP is consumed in metabolic processes

Answer 5

converted to ADP or AMP

Question 6

function of double helix in DNA

Answer 6

protection

Question 7

GC rich sequences

Answer 7

higher thermal stability due to greater no. of H bonds

Question 8

which nitrogenous base is different in RNA?

Answer 8

uracil (unmethylated form of thymine)

Question 9

mRNA

Answer 9

carries genetic material from nucleus to ribosome

Question 10

tRNA

Answer 10

delivers amino acids to ribosomes

Question 11

rRNA

Answer 11

links amino acids to make protein

Question 12

lagging strand

Answer 12

other direction

DNA polymerase can’t continuously synthesise strand - produce Okazaki fragments

Question 13

Okazaki fragments

Answer 13

short segments of DNA each starting with primer

later join to form continuous strand

Question 14

components of PCR

Answer 14

1. DNA template (contains target region to amplify)
2. DNA polymerase (heat-resistant)
3. DNA primers (need 2 which are complementary to 3’ end of each strand of DNA)
4. deoxynucleoside triphosphates (dNTPs) - building blocks for DNA polymerase to synthesise new strand

Question 15

what solution does PCR take place in?

Answer 15

buffer solution

suitable for enzymes

Question 16

PCR procedure

Answer 16

1. Denaturation (96C)
   - denatures DNA strand to provide single-stranded template
2. Annealing (55-65C)
   - primers bind to comp. sequences on single-stranded template
3. Extension (72C)
   - DNA polymerase synthesises new DNA strand comp. to DNA strand after adding free comp. dNTPs from reaction mixture

+ REPEAT

Question 17

gel electrophoresis

Answer 17

checks whether PCR has been done correctly

separation of PCR products
- compared with DNA ladder = molecular weight marker

DNA visualised with stain under UV light

Question 18

advantages of PCR

Answer 18

simple

highly sensitive

produces millions of products

Question 19

disadvantages of PCR

Answer 19

prone to contamination (= false results)

requires information about target sequence to generate primers for selective amplification

DNA polymerases prone to error - can lead to mutations in sequences