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Biology > discovery of DNA and DNA replication > Flashcards

discovery of DNA and DNA replication Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

what is the mode of Dna replication

A

semi-conservative

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2
Q

who discovered the mode of dna replication

A

meselson and stahl

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3
Q

how does the semi-conservative mode of dna replication work?

A

each dna strand serves as a template and forms two “half” new strands

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4
Q

what kind of base pairing does the new strand follow

A

complementary base pairing rules

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5
Q

what are the other proposed models of dna replication

A

conservative and dispersive replication

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6
Q

what is the conservative replication model?

A

two strands of the original molecule serve as template then rewind into old molecule and new molecule

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7
Q

what is the dispersive replication model?

A

both chains of replicated molecules contain old and new segments

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8
Q

how did melson and stahl discover that dna is semi-conservative

A

grew bacterial cells in heavy nitrogen, then switched to lighter nitrogen and extracted DNA at various time intervals and observed their densities

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9
Q

is nitrogen 15 heavier or lighter than nitrogen 14

A

heavier

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10
Q

during melson and stahl’s experiment, what time intervals did they check the DNA density and how many rounds had it gone through?

A

0 min- 0 rounds
20 min- 1 round
40 min- 2 rounds

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11
Q

what round(s) did the dispersive DNA match the results

A

O and 1 rounds

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12
Q

what round(s) did the conservative DNA match the results

A

0 round

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13
Q

what do DNA polymerases assemble?

A

complementary polynucleotide chains from individual deoxyribonucleotides

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14
Q

what are the four different polymerases used (deoxyribonucleotide triphosphates)

A

dATP, dGTP, dCTP, and dTTP (one for each base)

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15
Q

DNA polymerase adds a nucleotide to which end of the nucleotide chain

A

3’ end (exposed hydroxyl group)

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16
Q

the oldest end of DNA has an exposed what

A

5’ triphosphate

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17
Q

the newest end of DNA strand has a what

A

3’-OH group

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18
Q

DNA polymerase assemble nucleotide chains in what directions

A

5’-3’ direction

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19
Q

which way to DNA strands run in comparison to other

A

antiparallel

20
Q

what are the 3 things dna replication requires?

A

something to copy (parental DNA molecule)
someting to do the copying (enzymes)
building blocks to make copy (nucleotide triphosphates)

21
Q

what was the hammerling experiment?

A

green alga cells were cut into pieces and observed to see which were able to express hereditary info

22
Q

what did hammerling’s reciprocal graft experiment discover?

A

discovered hereditary info is stored in the cell’s nucleus

23
Q

who discovered smooth and rough strain?

A

frederick griffith

24
Q

was smooth strain or rough strain highly infective/pathogenic?

A

smooth strain

25
Q

where the s cells still alive even if the mouse died in griffith’s experiment? were the r cells?

A

yes to s cells, no to r cells

26
Q

if mice are infected with heat-killed s cells, what is expected to happen?

A

the mouse will live

27
Q

what if the mice are infected with heat-killed s cells and live r cells? why does this happen?

A

the mouse dies
the transforming principle: live r cells can be converted to live s cells because of some factor present in and derived from dead s cells

28
Q

what did oswald avery discover?

A

the chemical nature of griffith’s transforming principle=DNA

29
Q

oswald avery destroyed RNA, proteins, and DNA at different points to see which had the transforming principle

A

true

30
Q

what did hershey and chase do in their experiment?

A

labeled DNA and protein with radioactive isotope tracer (32P for DNA, 35S for protein)

31
Q

what is a bacteriophage?

A

virus that can infect bacteria

32
Q

how does infection by a virus occur?

A

when the virus injects DNA into the bacterial cell

33
Q

what do bacteriaphages cause to bacteria?

A

lysis

34
Q

how does lysis happen in bacteria?

A

when the virus DNA is inserted into the bacterial cell, it begins to replicate. once replication is complete, virions form (viral DNA and proteins assemble). the formation of the virions and the sheer number of them causes lysis

35
Q

what was the hershey-chase experiment conclusion?

A

only DNA entered the cell and appeared in progeny phages

36
Q

what percentage of radioactive proteins were found in the progeny phages?

A

less than 1%. most of it in the supernatant

37
Q

what percentage of radioactive DNA was found in the progeny phages?

A

greater than 30%. most of it in the pellet

38
Q

who discovered that DNA has a helical shape, using x-ray diffraction?

A

rosalind franklin

39
Q

rosalind franklin discovered that DNA has a helical shape and that the molecule has a diameter of 3.4 nm and makes a complete turn of helix every 2 nm.

A

false. the diameter is 2 nm, and it turns every 3.4 nm

40
Q

what did watson and crick do?

A

created a DNA model structure and explained how genetic information is stored and replicated

41
Q

what evidence did watson and crick use to deduce the structure of DNA?

A

Chargaff, Franklin, and Wilkens

42
Q

what is the difference between purines and pyrimidines?

A

purines have 2 rings, pyrimidines have one

43
Q

which nitrogenous bases are purines? which are pyrimidines?

A

purines: adenine, guanine
pyrimidines: cytosine, thymine, uracil

44
Q

what is the difference between adenine and guanine?

A

adenine has an amine while guanine has an oxygen

45
Q

what is the difference between cytosine, thymine, and uracil?

A

cytosine has an amine
thymine has a methyl and oxygen
uracil has an oxygen

46
Q

how many H bonds are between A and T/U versus G and C?

A

A=T (2)
G=-C (3)

47
Q

what are chargaff’s rules?

A

amount of adenine=amount of thymine
amount of cytosine=amount of guanine
always an equal proportion of purines and pyrimidines
A=T, G=C, A+G=C+T

Biology (14 decks)

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