Answer:
DNA may be taken up by bacterial cells and be active.
Explanation:
To understand Avery, MacLeod, and McCarty's experiment, it is important to know Frederick Griffith's precursor experiment. The microbiologist worked at the British Ministry of Health's Pathology Laboratory with pneumococci (commonly known as the bacterium Streptococcus pneumoniae, then known as Pneumococcus, which causes pneumonia), which were previously classified into several types. When cultured in petri dishes in the laboratory, the pneumococci that synthesize their capsules generate 'smooth' colonies. Subcutaneous injection of liquid culture of these pneumococci into mice causes their death. However, in vitro culture also allows the emergence of rough colonies', whose bacteria have lost the ability to synthesize mucopolysaccharide (and therefore have no capsules). Rough mutants could no longer be classified with sera and, moreover, lost their virulence: mice inoculated with them remained alive, unlike inoculated with smooth pneumococci.
The nature of Griffith's transforming principle remained unclear until the work of Avery, MacLeod, and McCarty. They repeated the in vitro transformation of pneumococci at the Rockfeller Institute for Medical Research, but replaced heat-dead cells with a purified fraction of smooth bacterial extract (unable to cause disease alone) and treated the material with different enzymes, each capable of destroying a specific type of macromolecule. Experience has shown that this fraction retained its transforming capacity when treated with protein or RNA degrading enzymes, but lost that ability when treated with DNA degrading enzymes. These results indicated that the chemical nature of the 'transforming principle' was DNA.
Thus, we can conclude that in addition to identifying genetic material, Avery, MacLeod and McCarty experiments with different strains of Streptococcus pneumoniae demonstrated that DNA can be absorbed by bacterial cells and be active.
Answer:
The correct answer is B) Yellow fever
Explanation:
Yellow fever is a viral disease and this disease is spread by the bite of female Aedes aegypti mosquitoes that are found in Brazil and many other South American countries and the chances of getting yellow fever gets increase when anyone travels through amazon river.
The symptoms of yellow fever disease are fever, headache, back pain, nausea, and in some people it causes liver damage which results in yellowing of the skin.
So if anyone is traveling to Brazil in South America then he must be vaccinated for yellow fever which is also recommended by the WHO and CDC. Therefore yellow fever would be the disease that the student would most likely to have.
The two sides of a nerve cell membrane have unequally distributed ions ( Na+ and K+). Sodium is inside, while potassium is outside. Carriers actively transport them. This active transport mechanism is called Sodium-Potassium Pump. Without stimulus, sodium channels are closed while some of the potassium channels are open.
Stimulus (depolarization) will cause the sodium channels to briefly open and the positively-charged ion diffuses into the nerve cell. The membrane potential becomes positive. The potassium channels open and positively-charged potassium diffuse out. With respect to the outside, the inside will become less positive again.
Your answer is correct. Chitin provide the strength to insect exoskeletons. Cellulose is the strength for plant. Starch and glycogen are energy sources for life.
