Paragraph 1: Semiconservative replication - each strand is an equal mix of old and new DNA.
Paragraph 2: In the past, other methods were suggested. Two opposing methods: conservative replication model and Dispersive replication model.
Paragraph 3: Meselson-Stahl experiment allowed scientists a way to distinguish between old and new DNA -- eliminating possibility of conservative replication. Later on, dispersive replication was also eliminated.
Paragraph 4: Watson and Crick confirmed semiconservative -- actually only a hypothesis. Later on confirmed by Meselson and Stahl.
_________________________________The author mentions that eukaryotes replicate through semiconservative replication in order to make the point that
A) the choice of E. coli bacteria was a good one for the Meselson-Stahl experiment
B) semiconservative replication depends on an organism having a complex cell structure
C) Watson and Crick realized that their work would have implications for humans
D) the Meselson-Stahl had implications for forms of life beyond simple bacteriaE) each DNA molecule in a eukaryote is incorporated in one chromosome
"This eliminated the possibility of dispersive replication, which would have produced DNA that was all of a density between the light and exactly intermediate DNA. E. coli are bacteria, and are thus prokaryotes, organisms that lack complex cell structures, but semiconservative replication also occurs in eukaryotes, organisms with complex cells such as animals and plants"
The sentences above suggest that the experiment impacted more than simple bacteria.
_________________________________According to the passage, which of the following is the reason that, had the conservative model been correct, the same number of heavy and light strands of DNA would have resulted?
A) Conservative replication breaks up the original DNA into small segments.
B) An equal mix of old and new DNA is formed using the conservative model.
C) Conservative replication would keep the original strands untouched.D) The double helix of DNA is separated only in the conservative model of replication.
E) The conservative replication model splits the original DNA into four discrete strands.
Paragraph 2 states "In the conservative replication model, a completely new double helix would be formed, leaving the original intact." The original stands are left untouched.
_________________________________It can be inferred from the passage that in the Meselson-Stahl experiment, a third generation of bacteria would produce bacteria with
A) some light density and some intermediate density DNAB) some light density and some heavy density DNA
C) some heavy density and some intermediate density DNA
D) only light density DNA
E) only intermediate density DNA
We have 3 densities: heavy, intermediate, light.1 generation: intermediate to the heavy and light DNA.
2 generations: half intermediate and half light (no more heavy)
A third generation would produce bacteria with some light density and some intermediate density DNA. Answer is A.
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