Answer:
Because natural selection selects for it. Thus it persists.
Explanation:
You have to understand heterozygote advantage. Basically, it's where heterozygotes have an advantage over homozygotes. In the case of sickle cell disease, heterozygotes have an advantage, and natural selection favors whatever is advantageous. Thus, because heterozygotes each have one recessive sickle-cell allele, as natural selection favors the heterozygotes, the recessive sickle-cell allele persists and remains in the gene pool.
Griffith's experiment worked with two types of pneumococcal bacteria (a rough type and a smooth type) and identified that a "transforming principle" could transform them from one type to another.
At first, bacteriologists suspected the transforming factor was a protein. The "transforming principle" could be precipitated with alcohol, which showed that it was not a carbohydrate. But Avery and McCarty observed that proteases (enzymes that degrade proteins) did not destroy the transforming principle. Neither did lipases (enzymes that digest lipids). Later they found that the transforming substance was made of nucleic acids but ribonuclease (which digests RNA) did not inactivate the substance. By this method, they were able to obtain small amounts of highly purified transforming principle, which they could then analyze through other tests to determine its identity, which corresponded to DNA.
Option 3
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Answer:
1. Aorta
2. Left atrium
3. Right ventricle
4. The pulmonary artery
5. Left ventricle.
Explanation:
The aorta is the main artery of the body that carries the oxygen-rich blood to all the body parts except the lungs from the left ventricle. It is divided into main coronary arteries or blood vessels.
The left atrium is one of the heart chambers, it is located in the upper part of the heart on the right side that receives the oxygenated blood from the lungs through the pulmonary vein.
The right ventricle is the chamber of the heart that pumps the deoxygenated blood to the pulmonary valve to MPA to the lungs to get oxygenated.
The pulmonary artery or the main PA (MPA) carries the oxygen-depleted blood from the right ventricle into the lungs, where blood becomes oxygenated.
The Left ventricle is the thickest muscle chamber of the heart responsible for the pumping oxygen-rich blood to the circulatory system and to the body through the aorta.
The wall of the heart<span> consists of three </span>layers<span>: the epicardium (external </span>layer<span>), the myocardium (middle </span>layer<span>) and the endocardium (inner </span>layer<span>). The epicardium is the thin, transparent </span>outer layer<span> of the wall and is composed of delicate connective tissue.
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