Answer:
D. astigmatism
Explanation:
Astigmatism is an imperfection in the curvature of the eye. Most of the focusing power in the eye occurs along the frontal surface called the cornea. The next structure involved in focusing is the lens, which lies behind the iris inside the eye.
The ideal cornea has a symmetrically curved surface, like a basketball. Astigmatism is caused by a cornea or lens with a curve that is not symmetrical. As a result, people with astigmatism may have distorted or blurred vision.
Astigmatism can occur in families and in most cases is associated with other refractive problems such as nearsightedness or farsightedness. It may also increase over time due to age.
Answer:
means that both the necessary mRNAs must persist and there must be a low level of RNA-degrading enzymes present
Explanation:
Mature red blood cells (also known as erythrocytes) don't contain nuclei. The red blood cells that enter the bloodstream eject their nuclei in order to have more space for transporting hemoglobin, a protein whose main function is to bind molecular oxygen. Erythrocytes have a life span period of three (3) to four (4) months. During this period, the mRNA of the hemoglobin genes must remain intact in order to synthesize hemoglobin proteins (i.e., their subunits). Moreover, in mature red blood cells, the levels of the enzymes involved in the degradation of cytoplasmic mRNA (ribonucleases) must also be low to avoid bulk mRNA degradation.