biological molecules (DNA and RNA)

Question 1

what does DNA stand for?

Answer 1

deoxyribonucleic acid

Question 2

what does RNA stand for?

Answer 2

ribonucleic acid

Question 3

what is the purpose of DNA?

Answer 3

stores genetic information

Question 4

what is the purpose of RNA?

Answer 4

transfers genetic information from DNA to ribosomes

Question 5

what is a nucleotide?

Answer 5

type of biological molecule

Question 6

what is a nucleotide made from?

Answer 6

pentose sugar, nitrogen containing base, phosphate group

Question 7

what is the pentose sugar in DNA?

Answer 7

deoxyribose

Question 8

what bases are present in DNA?

Answer 8

adenine, thymine, cytosine, guanine

Question 9

what is the pentose sugar in RNA?

Answer 9

ribose

Question 10

what bases are present in RNA?

Answer 10

adenine, uracil, cytosine, guanine

Question 11

what is a polynucleotide?

Answer 11

polymer of nucleotides

Question 12

how do nucleotides join?

Answer 12

condensation reaction between phosphate of one molecule, and the sugar of another
phosphodiester bond

Question 13

what is a chain of sugars and phosphates called?

Answer 13

sugar phosphate backbone

Question 14

what is the structure of DNA?

Answer 14

double helix, 2 polynucleotide strands that are antiparallel

Question 15

what bonds form between DNA bases?

Answer 15

hydrogen

Question 16

what is complementary base pairing?

Answer 16

the idea that each base can only join with its complementary base

Question 17

how many hydrogen bonds form between A and T?

Answer 17

2

Question 18

how many hydrogen bonds form between C and G?

Answer 18

3

Question 19

who proposed the structure of the DNA double helix?

Answer 19

Watson and Crick

Question 20

what is the structure of RNA?

Answer 20

short polynucleotide chain

Question 21

how does semi conservative DNA replication occur?

Answer 21

1) DNA helicase breaks hydrogen bonds between bases on polynucleotide strands
2) DNA helix unwinds to form 2 strands
3) original strand acts as a template
4) complementary base pairing occurs- free nucleotides are attracted to their exposed bases
5) condensation reaction joins nucleotides (catalysed by DNA polymerase)

Question 22

which end of the newly forming strand is the active site of DNA polymerase complementary to?

Answer 22

3’ end (enzyme can only add nucleotides at this end)

Question 23

which direction is a new strand of DNA made in?

Answer 23

5’ to 3’ direction
DNA polymerase moves down the template strand in the 3’ to 5’ direction
as strands are antiparallel, DNA polymerase works in opposite directions on either strand

Question 24

who proposed evidence for semi conservative replication?

Answer 24

Meselson and Stahl

Question 25

what isotopes of nitrogen did Meselson and Stahl use?

Answer 25

heavy nitrogen= 15N

light nitrogen= 14N

Question 26

how did Meselson and Stahl provide evidence for semi conservative replication?

Answer 26

initial DNA samples contained light or heavy nitrogen
heavy nitrogen bacteria were replicated in light nitrogen broth
spun in a centrifuge
DNA with a combination of heavy original strands and light new strands settled in the middle of the test tube