You can also calculate the percentage of adenine when given the percentage of guanine or cytosine. Since you know there are only four bases in DNA, all four bases together must equal 100 percent of the sample. If given the information that the sample is 20 percent guanine, you can surmise it is also 20 percent cytosine since guanine and cytosine pair with each other. Together, that is 40 percent of the total sample. You can subtract that 40 percent from 100 percent and determine 60 percent of the sample must be adenine and thymine together. Since those two bases always exist in equal concentrations, you know the DNA sample is 30 percent adenine.
<em>Answer is B. The fossils in the lower layers are older than the fossils in the upper layers.</em>
The patients skin laceration healed nicely leaving a cicatrix, which is a scar.
A cicatrix is the scar of a healed wound - when you have a deep wound, and it gets stitched/heals on its own, after a while, that wound is going to transform into a cicatrix, which is just a fancy medical term for a scar.
