Answer:
Semi-conservative replication
Explanation:
After the double-helix discovery of Watson and Crick, there were three possible models about the DNI replication:
- The Conservative model stated that the two strands of DNI together were the template of another new molecule. The final product was the original double-stranded molecule and the new molecule.
- The semi-conservative model stated that the original DNI molecule separated into two strands, and each of them served as a template for the synthesis of a new complementary strand. The replication product would be two double-stranded DNA molecules, each carrying an original strand a new one.
- The Dispersive moles stated that the replication product would be two molecules made by a mixture of segments of the original and the new molecules.
Meselson and Stahl joined to discover which of the models was the correct one. To do it they used E. coli and Nitrogen isotopes.
- First, they extracted DNI from bacteria grown in a medium with N¹⁴ and got its density band by centrifugation.
- Then they grew bacteria in a medium with N¹⁵, extracted their DNI molecules, centrifugated them, and got the density band, which was heavier than the firsts ones.
- The researchers then transferred bacteria grown in medium with N¹⁵ to a medium with N¹⁴, and they allowed only one replication process to occur. DNI was extracted and centrifugated again, and a new band appeared. This band was an intermediate form between bands of DNI-N¹⁵ and DNI-N¹⁴.
This event <em>eliminated the conservative model</em>. If this model were correct, the expected result would be to get two bands: one corresponding to the density DNI-N¹⁵ and the other corresponding to the density DNI-N¹⁴.
- Bacteria grown in a medium with N¹⁵ and then transferred to a medium with N¹⁴ were finally allowed to replicate twice. Their DNI was extracted and centrifugated. The result was two bands: one of them coincided with the intermediate band, and the other one with the DNI-N¹⁴.
<u>This result was conclusive</u> because if the dispersal model were correct, these two bands should not appear, as all the DNI strands would have part of the original molecule.
With this experiment, Meselson and Stahl proved that the correct replication model was the semi-conservative one.
Answer: Option C
Explanation:
The main reason by which the ocean currents are formed is the rotation of earth. The earth rotates on its own axis and due to this reason there is a huge mixing of the water from the equator and poles which is termed as ocean currents.
Ocean currents are important as it controls the global temperature. The water at the equator is hot and the water at poles are cold.
Due to the rotation of the earth the water and air moves from the colder regions towards the hotter region and hotter to colder and this causes ocean currents.
Answer:
Both male and female gametes are created during the process of meiosis. The formation of male gametes or sperm is called spermatogenesis. After telophase II of spermatogenesis, there would be <u>four</u> male gametes created that are all genetically <u>haploid.</u>
Explanation:
Telophase II is the final step in Meiosis II. In Telophase II of the spermatogenesis chromosomes travels to opposite poles and are covered by a nuclear envelop. The two parent cells result four daughter cells which are haploid (1n).
The answer is "Carnation" because it is sensitive to the presence of ethylene gas. Rose is also one example. However it is the Carnation that the one that cut flower emits unusual large amount of ethylene gas.
<span>Carnation is also known as ornamental flowers.</span>
All of the atoms lalalalala
