discovery of DNA and DNA replication

Question 1

what is the mode of Dna replication

Answer 1

semi-conservative

Question 2

who discovered the mode of dna replication

Answer 2

meselson and stahl

Question 3

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

Answer 3

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

Question 4

what kind of base pairing does the new strand follow

Answer 4

complementary base pairing rules

Question 5

what are the other proposed models of dna replication

Answer 5

conservative and dispersive replication

Question 6

what is the conservative replication model?

Answer 6

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

Question 7

what is the dispersive replication model?

Answer 7

both chains of replicated molecules contain old and new segments

Question 8

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

Answer 8

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

Question 9

is nitrogen 15 heavier or lighter than nitrogen 14

Answer 9

heavier

Question 10

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

Answer 10

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

Question 11

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

Answer 11

O and 1 rounds

Question 12

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

Answer 12

0 round

Question 13

what do DNA polymerases assemble?

Answer 13

complementary polynucleotide chains from individual deoxyribonucleotides

Question 14

what are the four different polymerases used (deoxyribonucleotide triphosphates)

Answer 14

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

Question 15

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

Answer 15

3’ end (exposed hydroxyl group)

Question 16

the oldest end of DNA has an exposed what

Answer 16

5’ triphosphate

Question 17

the newest end of DNA strand has a what

Answer 17

3’-OH group

Question 18

DNA polymerase assemble nucleotide chains in what directions

Answer 18

5’-3’ direction

Question 19

which way to DNA strands run in comparison to other

Answer 19

antiparallel

Question 20

what are the 3 things dna replication requires?

Answer 20

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

Question 21

what was the hammerling experiment?

Answer 21

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

Question 22

what did hammerling’s reciprocal graft experiment discover?

Answer 22

discovered hereditary info is stored in the cell’s nucleus

Question 23

who discovered smooth and rough strain?

Answer 23

frederick griffith

Question 24

was smooth strain or rough strain highly infective/pathogenic?

Answer 24

smooth strain

Question 25

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

Answer 25

yes to s cells, no to r cells

Question 26

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

Answer 26

the mouse will live

Question 27

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

Answer 27

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

Question 28

what did oswald avery discover?

Answer 28

the chemical nature of griffith's transforming principle=DNA

Question 29

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

Answer 29

true

Question 30

what did hershey and chase do in their experiment?

Answer 30

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

Question 31

what is a bacteriophage?

Answer 31

virus that can infect bacteria

Question 32

how does infection by a virus occur?

Answer 32

when the virus injects DNA into the bacterial cell

Question 33

what do bacteriaphages cause to bacteria?

Answer 33

lysis

Question 34

how does lysis happen in bacteria?

Answer 34

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

Question 35

what was the hershey-chase experiment conclusion?

Answer 35

only DNA entered the cell and appeared in progeny phages

Question 36

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

Answer 36

less than 1%. most of it in the supernatant

Question 37

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

Answer 37

greater than 30%. most of it in the pellet

Question 38

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

Answer 38

rosalind franklin

Question 39

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.

Answer 39

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

Question 40

what did watson and crick do?

Answer 40

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

Question 41

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

Answer 41

Chargaff, Franklin, and Wilkens

Question 42

what is the difference between purines and pyrimidines?

Answer 42

purines have 2 rings, pyrimidines have one

Question 43

which nitrogenous bases are purines? which are pyrimidines?

Answer 43

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

Question 44

what is the difference between adenine and guanine?

Answer 44

adenine has an amine while guanine has an oxygen

Question 45

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

Answer 45

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

Question 46

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

Answer 46

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

Question 47

what are chargaff's rules?

Answer 47

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