Answer:
Nitrogenous bases contain the genetic information, their amount is variable among different species, and the arrangement of these bases is also variable among different species
Explanation:
Both Watson-Crick and Pauling's DNA models considered that DNA nitrogenous bases (i.e., Adenine, Cytosine, Thymine and Guanine) contain the genetic information that determines the characteristics of living organisms. Moreover, both DNA models also considered that nitrogenous base composition varies between species, as well as the arrangement of these bases in the DNA chain also varies between species. Based on these features, Linus Pauling considered that a model where nitrogenous bases would be arranged on the outside of the DNA molecule would be easier for the DNA molecule to be replicated, transcribed, or repaired. Although incorrect, Pauling's DNA triple helix model was fundamental to develop the helical (double-stranded) structure of DNA, which was finally discovered by Watson and Crick in 1953.
Microscopical observations show the presence of simple in structure, abundant, and pervasive microorganisms. Researchers at the time came to the conclusion that there was a life force in the air.
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Nucleus, The “brains” of the cell, the nucleus directs cell activities and contains genetic material called chromosomes made of DNA.
Answer:
An earthquake
, a forest fire
, a hurricane and a volcanic eruption.
Explanation:
An earthquake
, a forest fire
, a hurricane and a volcanic eruption are the events that is responsible for the suitable conditions for primary succession because all the population of animals and vegetation are removed from an area and the new type of organisms is start to living in that new environment. These new organism has the ability to survive that environmental conditions. These events completely removed the population in the environment and provides conditions for primary succession.
Answer:
The correct answer is B. The virus can infect the host.
Explanation:
- As the host and the virus both remain in the agar plate, the virus is capable of infecting the host cells.
- The host cell multiplies and grows by utilising the nutrient from the agar medium.
- After the virus particles infect the host, they replicate inside the host and produce new progeny virions which get released out of the host cell by killing it.
- The newly formed virions infect other host cells and the process continues.
- The killing of the host cells by the viruses result in the generation of clear zones on the agar plate which is also known as the zone of exclusion.
- In the zone of exclusion region, the host cells have been killed by the viruses.
