Your answer is your third choice, critical injury
Answer:
In the case of HIV-1, this loss-of-function mutation has proven to be beneficial.
Explanation:
Loss-of-function mutations are those that result in a gene product that has less or no function compared to the unmutated gene. When the allele completely loses function, (null allele), it is called an amorphous mutation. Phenotypes associated with these mutations are usually recessive, except when the organism is haploid, or when the reduced dosage of the normal gene is not sufficient to produce a normal phenotype (this phenomenon is called haploinsufficiency).
As mentioned earlier, this type of mutation results in a defective gene, but the text shown in the above question shows an example of a beneficial loss-of-function mutation because this mutation provides resistance to HIV-1 infection.
Water is of major importance to all living things; in some organisms, up to 90% of their body weight comes from water. Up to 60% of the human adult body is water. According to H.H. Mitchell, Journal of Biological Chemistry 158, the brain and heart are composed of 73% water, and the lungs are about 83% water.
Answer:
The respiratory system includes the nose, mouth, throat, voice box, windpipe, and lungs.
Air enters the respiratory system through the nose or the mouth. If it goes in the nostrils (also called nares), the air is warmed and humidified. Tiny hairs called cilia (SIL-ee-uh) protect the nasal passageways and other parts of the respiratory tract, filtering out dust and other particles that enter the nose through the breathed air.
