Why would you expect equal numbers of guanine and cytosine in a molecule of DNA, but not necessarily in a molecule of RNA?

Equal numbers of guanine and cytosine would be expected in a molecule of DNA, but not RNA because:

In the double strand DNA, Adenine always pair with Thymine while Guanine always pair with Cytosine. Hence the number of Adenine must be equal to that of Thymine while that of Guanine must be equal to Cytosine.

The single strandness of RNA means that it can contain an arbitrary amount of any of the bases without following a particular rule.

More on RNA can be found here: link

DNA is double-stranded, so there must be equal numbers of C and G because they pair to each other on the complementary strands.

RNA is only single-stranded, so there can be any number of C and G. They don't pair to each other, because there's only one strand.

the correct answer is 4) heat and pressure

metamorphic rocks arise from transformation of existing rocks types, in a process called metamorphism. during metamorphism the original rock(prolith) change into metamorphic rock by heating (150-200c) and pressure of more than 1000 bar. the original rock can be sedimentary, igneous, or existing metamorphic rock.

interphase

the period of cell growth when the cell synthesizes new molecules and organelles. the cell is not dividing and it constitutes the majority of the time spent in the cell cycle

prophase

changes occur in the nucleus and cytoplasm. the chromatin condenses to form structures (sister chromatids) visible with a light microscope and the mitotic spindle begins to form, but the nucleus is still in tact

prometaphase

the nuclear envelope fragments and the spindle microtubules attach to the kinetochores of the sister chromatids

metaphase

all the cell's duplicated chromosomes are lined up at an imaginary plane equidistant between the poles of the mitotic spindle

anaphase

begins when sister chromatids separate from each other and ending when a complete set of daughter chromosomes arrives at each of the two poles of the cell

telophase

the daughter nuclei form at the two poles of a cell

cytokinesis

the division of a cytoplasm to form two separate daughter cells. usually occurs during telophase during mitosis. this and mitosis make up to mitotic (m) phase of the cell cycle