DNA

Question 1

How many basic components is DNA made up of and what are they called?

Answer 1

3- sugar (deoxyribose), phosphate group, organic base

Question 2

what do the components combine to form?

Answer 2

nucleotide

Question 3

what are the four different organic bases and what are the two groups?

Answer 3

Single-ring bases: cytosine, thymine

double-ring bases: guanine, adenine.

Question 4

what reaction combines the basic components?

Answer 4

condensation reaction

Question 5

what are two combined nucleotides called?

Answer 5

dinucleotide

Question 6

between which two components is the condensation reaction between?

Answer 6

deoxyribose and phosphate group

Question 7

how are the organic base pairs joined?

Answer 7

with hydrogen bonds

Question 8

what do organic bases contain?

Answer 8

nitrogen

Question 9

what are the two base pairs?

Answer 9

adenine + thymine. guanine + cytosine

Question 10

how many hydrogen bonds are between guanine and cytosine?

Answer 10

3

Question 11

how many hydrogen bonds are between thymine and adenine?

Answer 11

2

Question 12

adenine is ……………………. of thymine

Answer 12

complementary

Question 13

what are there specific pairs of organic bases?

Answer 13

guanine and adenine and longer than cytosine and thymine

Question 14

how many base pairs are there for each complete turn of the helix?

Answer 14

10

Question 15

why is it useful that DNA is very stable?

Answer 15

it cane be passed down from generation to generation with no change

Question 16

why is it useful that DNA is an extremely large molecule?

Answer 16

it carries an immense amount of genetic information

Question 17

what are the two other functions of DNA?

Answer 17

• 2 separate strands of DNA held by hydrogen bonds- can separate during DNA replication
• base pairs are within the helical cylinder- genetic info is somewhat protected from being corrupted by outside chemicals and physical forces

Question 18

who found that DNA was a hereditary material?

Answer 18

Griffith 1928

Question 19

what did Griffith do?

Answer 19

injected mice with two strains of bacteria that cause pneumonia

Question 20

what were the two strains of bacteria Griffith used?

Answer 20

S strain- smooth, capsuled caused pneumonia

R strain- rough, non capsuled, harmless

Question 21

what happened to the mice that were injected with heated S strain?

Answer 21

they survived

Question 22

what happened when the mice were injected with heated and killed S strain and live R strain?

Answer 22

They died

Question 23

what are the possible explanations of the mice dying after being injected with heated S strain and live R strain?

Answer 23

experimenter error and the R strain mutated (extremely unlikely)

Question 24

what was the conclusion of Griffith?

Answer 24

pneumonia is caused by a toxin. the dead S strain has info on how to make the toxin. TH live R strain has the means of making the toxin but lacks info how to.
presence of the S strain transformed the R strain into S strain, some agent from the killed S strain was passed onto the R strain.

Question 25

how do you separate DNA from cells?

Answer 25

• homogenise tissue
• add to salty solution, break down cell membrane
• denature DNAses in hot water bath- too long DNA denatures as well
• cool in ice
• filter
• collect 3 cm of filtrate-
• add 2-3 drops of PROTEASE
• add equal volume of cold ethanol on surface
• DNA strands gradually appear in the ethanol

Question 26

when separating DNA, why do you filter the homogenate?

Answer 26

get rid of cell debris- separate cell walls from DNA and proteins