Identify the steps of the carbon cycle

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 are the precautions that should be token when using a photometer? please help me

Maksim231197 [3]

Answer:

PRECAUTIONS FOR USING A SPECTROPHOTOMETER :

1 . By allowing the lamps and electronics to warm up

2.By cleaning up any spills inside the cuvette compartment

3.By carrying out the set-up procedure in the correct order

4.By ensuring that %T or transmission is used as appropriate

5.By closing the door to the cuvette compartment before reading the result

6.By performing calibration checks after set up

7.By wiping fingerprints and spilt sample off the outside of the cuvette before measuring

8.By using the correct wavelength

PRECAUTIONS FOR USING A FRAME PHOTOMETER:

1. Do not move or Carry the unit when in use or connected to the mains electricity supply

2. There should be sufficient time for the chimney to cool before handling

3. Do not use acetylene with the flame photometer

4. Over adjustment of the fuel valve will cause excess flame

Do not position the product so that it is difficult to disconnect from the mains supply

5. Do not cover the chimney whilst in use.

6. Do not block or obstruct ventilation slots /airways

7. Do not operate or handle any part of the product with wet hands

I HOPE THIS WILL HELP AND IF NOT LET ME KNOW

8 0

3 years ago

Fill in the blanks.

lbvjy [14]

1. Parasites

2. herbivores

3. phagocytosis

4. Plant

5. oxygen (O2)

6. gills

7. open

8. urea

9. Single-loop circulatory systems have one direction of blood flow. Typically in fish, oxygen is absorbed in the gills, flows in blood to the body organs, and back to the heart, which pumps it directly back to the gills. In double-loop circulatory systems, the heart has multiples of each chamber. Part of the heart pumps blood to the lungs, to get oxygen. This blood flows back to a different chamber where it then gets pumped to the body. Once its oxygen has been used up, it goes back to the heart to be pumped all over again to the lungs.

10. Freshwater animals have lower water and higher salt concentrations than the environment in their cells. This means water constantly tries to diffuse into the animals, which can bloat them. They have special cell processes that remove extra water.

pennfoster

5 0

3 years ago

'the fern are more terrestrially adapted 'explain this statement

Llana [10]

Answer:

The reason for this is that both moss and fern species are relatively primitive plants that are only Imperfectly adapted to a terrestrial environment. ferns have both roots and vascular tissue and therefore, can grow larger than moss species, but like the mosses, ferns require water for reproduction.

4 0

3 years ago

Original Chromosome: ABCJKL Which of the following depicts a

koban [17]

Answer:

A.)

Explanation:

5 0

3 years ago