15 points to the first correct.

Meselson and Stahl used density labeling of DNA to show that DNA replication occurs via a semiconservative mechanism. In their e

cricket20 [7]

Answer:

The organism previously used 15N for replication so all the DNA molecules were of 15N15N type. Then the organism is shifted to a medium where only 14N is available for replication.
According to semi conservative mode of replication, a newly synthesised DNA molecule consists of one new strand and one parental strand. So after the first round of replication, All the 15N strands will synthesise new DNA strands using 14N resulting into intermediate 15N14N DNA molecules. Hence, only one band would be observed (15N14N) above the original 15N15N band since 15N14N has lighter isotope too so it will be lighter than 15N15N molecules and will lie above it.
After second round of replication, 15N strand from 15N14N would synthesise another 14N strand. 14N strand from 15N14N molecules will also synthesise another 14N strand. So now, 50% of the DNA molecules will be of 15N14N intermediate type and 50% of them will be of 14N14N type.Two bands will be observed above the original 15N15N band. One band of 15N14N molecules will be right above it and other band of 14N14N molecules will be even higher because it is the lightest band since it has only the lighter isotope of nitrogen.

8 0

3 years ago

What processes occur during G2 phase? Choose all which apply.

Inessa [10]

Explanation:

the last part of interphase is called the G2 phase. The cell has grown, DNA has been replicated, and now the cell is almost ready to divide. This last stage is all about prepping the cell for mitosis or meiosis. During G2, the cell has to grow some more and produce any molecules it still needs to divide.

4 0

2 years ago

Which had the most control of traits and Inheritance

Vera_Pavlovna [14]

The correct answer is:

nucleic acids

Explanation:

Nucleic acids are biopolymers, or humble biomolecules, necessary for all known methods of life. They are formed of nucleotides, which are monomers comprised of three components: a 5-carbon sugar, a phosphate group, and a nitrogenous base..Nucleic acids are the basic unit of heritage, they develop all the genetic element of living things.This genetic information defines how individual cells and entire organisms grow and function

5 0

3 years ago

In humans, the quadriceps muscle is a skeletal leg muscle under voluntary control. As such, it contracts in response to signals

Masja [62]

Answer:

The correct answer is - operation of reflex arc.

Explanation:

The reflex arc is a unique and special type of neural pathway that starts with a sensory neuron and ends with a motor neuron. In this operation sensory neuron acts as the receptor and motor neuron is effector. This type of neural circuit helps in faster response.

Voluntary muscles like quadriceps muscle are normally in control voluntarily however, such muscle may contract involuntary due to reflex arc. This type of contraction takes place before the signal has even reached the brain.

In this response the sensory neuron takes the signal to the spinal cord and then motor neuron to the effector muscle for faster response.

Thus, the correct answer is - operation of reflex arc.

8 0

3 years ago

How many nuclei does a prokaryotes cell contain

Marrrta [24]

prokaryotic cells do not have a nucleus.

7 0

2 years ago

Read 2 more answers