In the modern world, what is the path for the transfer of genetic material? B. DNA-RNA-Protein

consider how they arose in evolution. The most fundamental of all such problems is the expression of hereditary information, which today requires extraordinarily complex machinery and proceeds from DNA to protein through an RNA intermediate. How did this machinery arise? One view is that an RNA world existed on Earth before modern cells arose (Figure 6-91). According to this hypothesis, RNA stored both genetic information and catalyzed the chemical reactions in primitive cells. Only later in evolutionary time did DNA take over as the genetic material and proteins become the major catalyst and structural component of cells. If this idea is correct, then the transition out of the RNA world was never complete; as we have seen in this chapter, RNA still catalyzes several fundamental reactions in modern-day cells, which can be viewed as molecular fossils of an earlier world.

Figure 6-91. Time line for the universe, suggesting the early existence of an RNA world of living systems.

Figure 6-91

Time line for the universe, suggesting the early existence of an RNA world of living systems.

high growth (apex)

you know that this symptom is misleading and quite often is related to: heart attack

a heart attack is a condition that occurs when the blood flow that transports oxygen to the heart muscle is damaged or cut off completely. the coronary arteries that supply the heart muscle with blood flow can be blocked by the accumulation of plaque. also, when the plaque within the heart artery breaks, it creates blood clot that can also hinder the blood flow. men that are over 45years of age and women that are over 55years of age are at risk of having a heart attack. the symptoms of a heart attack include chest discomfort, chest pain, coughing, and shortness of breath.