Answer:
A DNA marker
Explanation:
also known as a size standard or a DNA ladder) is loaded into the first well of the gel. The fragments in the marker are of a known length so can be used to help approximate the size of the fragments in the samples.
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Answer:
C.
Explanation:
All these carbon atoms are isotopes: they have the same amount of protons (in this case, 6 because carbon always has 6 protons) and the same amount of electrons (6 because the carbons given have a neutral charge).
Therefore, the only thing we are changing is the atomic mass and the amount of neutrons present in each isotope.
In Carbon-12, there are 6 protons, 6 neutrons, and 6 electrons.
In Carbon-13, there are 6 protons, 7 neutrons, and 6 electrons.
In Carbon-14, there are 6 protons, 8 neutrons, and 6 electrons.
The heart is beneath the breastbone in the chest cavity of the frog