DNA Flashcards
How many basic components is DNA made up of and what are they called?
3- sugar (deoxyribose), phosphate group, organic base
what do the components combine to form?
nucleotide
what are the four different organic bases and what are the two groups?
Single-ring bases: cytosine, thymine
double-ring bases: guanine, adenine.
what reaction combines the basic components?
condensation reaction
what are two combined nucleotides called?
dinucleotide
between which two components is the condensation reaction between?
deoxyribose and phosphate group
how are the organic base pairs joined?
with hydrogen bonds
what do organic bases contain?
nitrogen
what are the two base pairs?
adenine + thymine. guanine + cytosine
how many hydrogen bonds are between guanine and cytosine?
3
how many hydrogen bonds are between thymine and adenine?
2
adenine is ……………………. of thymine
complementary
what are there specific pairs of organic bases?
guanine and adenine and longer than cytosine and thymine
how many base pairs are there for each complete turn of the helix?
10
why is it useful that DNA is very stable?
it cane be passed down from generation to generation with no change
why is it useful that DNA is an extremely large molecule?
it carries an immense amount of genetic information
what are the two other functions of DNA?
- 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
who found that DNA was a hereditary material?
Griffith 1928
what did Griffith do?
injected mice with two strains of bacteria that cause pneumonia
what were the two strains of bacteria Griffith used?
S strain- smooth, capsuled caused pneumonia
R strain- rough, non capsuled, harmless
what happened to the mice that were injected with heated S strain?
they survived
what happened when the mice were injected with heated and killed S strain and live R strain?
They died
what are the possible explanations of the mice dying after being injected with heated S strain and live R strain?
experimenter error and the R strain mutated (extremely unlikely)
what was the conclusion of Griffith?
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.
how do you separate DNA from cells?
- 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
when separating DNA, why do you filter the homogenate?
get rid of cell debris- separate cell walls from DNA and proteins
