Answer:
Explanation:
The original has hybrid 15N/14N DNA, and the second generation has both hybrid 15N/14N DNA and 14N/14N DNA. No 15N/15N DNA was observed. In this experiment:
Nitrogen is a significant component of DNA. 14N is the most bounteous isotope of nitrogen, however, DNA with the heavier yet non-radioactive and 15N isotope is likewise practical.
E. coli was developed for several generations in a medium containing NH4Cl with 15N. When DNA is extracted from these cells and centrifuged on a salt density gradient, the DNA separates at which its density equals to the salt arrangement. The DNA of the cells developed in 15N medium had a higher density than cells developed in typical 14N medium. After that, E. coli cells with just 15N in their DNA were transferred to a 14N medium.
DNA was removed and compared to pure 14N DNA and 15N DNA. Immediately after only one replication, the DNA was found to have an intermediate density. Since conservative replication would result in equal measures of DNA of the higher and lower densities yet no DNA of an intermediate density, conservative replication was eliminated. Moreso, this result was consistent with both semi-conservative and dispersive replication. Semi conservative replication would result in double-stranded DNA with one strand of 15N DNA, and one of 14N DNA, while dispersive replication would result in double-stranded DNA with the two strands having mixtures of 15N and 14N DNA, either of which would have appeared as DNA of an intermediate density.
The DNA from cells after two replications had been completed and found to comprise of equal measures of DNA with two different densities, one corresponding to the intermediate density of DNA of cells developed for just a single division in 14N medium, the other corresponding to DNA from cells developed completely in 14N medium. This was inconsistent with dispersive replication, which would have resulted in a single density, lower than the intermediate density of the one-generation cells, yet at the same time higher than cells become distinctly in 14N DNA medium, as the first 15N DNA would have been part evenly among all DNA strands. The result was steady with the semi-conservative replication hypothesis. The semi conservative hypothesis calculates that each molecule after replication will contain one old and one new strand. The dispersive model suggests that each strand of each new molecule will possess a mixture of old and new DNA.
Escape velocity is the velocity an object needs to escape the gravitational influence of a body if it is in free fall, i.e. no force other than gravity acts on it. Your rocket is not in free fall since it is using its thruster to maintain a constant velocity so the notion of "escape velocity" does not apply to it.
Answer:
1. The reason why nichrome wire is used in a heater is due to the properties of nichrome which makes it a material of choice for heating application including;
i) The cost of manufacture of nichrome is low
ii) Nichrome has both high mechanical and creep strength, and therefore is suitable for installation and use in a wide setting
iii) Nichrome has a high resistance to electron flow, making it a good electrical heating element
iv) Nichrome has a high resistance to oxidation, such that it can be reused several times as a heater
v) The high ductility of nichrome allows it to be stretched and drawn around different vessels with contents to which heat is to be supplied
2. Copper wire is not used in heaters because according to Joule's law, the heat produced from the flow of electric current, 'I', through a material having a resistance, 'R', for a time, 't', is proportional to I²·R·t, and copper has a very low resistance, 'R', to the flow of electric current, and therefore, will not produce sufficient heat required at a given current level
Explanation:
Answer:
B. neutrons
Explanation:
When a free neutron hits the nucleus of a fissile atom like uranium-235 (235U), the uranium splits into two smaller atoms called fission fragments, plus more neutrons. Fission can be self-sustaining because it produces more neutrons with the speed required to cause new fissions. This creates the chain reaction.
Answer:
4.) the dependent variable is the french fry
5.) the independent variable is the jar; whether it has a lid on or not
6.) there are plenty of control variables in this example, the type of jar (size, material of the jar, etc.), the type of french fry, the room that the jars are in, the air pressure in the room, how long the experiment is, etc.
7.) My conclusion would be that the french fry that has the most exposure to the air.
The moisture in the french fry is leaving the jar because it is exposed to the open air. It becomes stale. But because the other french fry is in the closed jar, it is not exposed to the air or any new type of bacteria that could've entered the open jar. It'll stay fresher longer because it is not exposed the way the fry in the open jar is.
Explanation:
The dependent variable is the variable that is being tested. It is the one that changes due to whatever is being placed upon it.
- i.e. the dependent variable in an experiment that tests the growth rate of lima bean plants in different colored lighting is the lima bean plant. <em>Depending</em> on the color of the lighting, the lima bean plant will grow at different rates.
The independent variable is the variable that is changed or controlled by an experimenter
- i.e. the independent variable in an experiment that tests the growth rate of lima bean plants in different colored lighting is the different colored lighting. The color of the lighting helps prove the hypothesis that the growth rate of a lima bean plant is dependent on the lighting. In other words, the color of the light is not dependent on the growth of the plant.
A control variable is a variable that cannot be changed and is constant throughout the entire experiment
- i.e. temperature, gravity, pollutants in the air, air pressure, humidity, etc.
