True, though the Hadean period is one exception.
The right answers are:
A-present in eukaryotic genomes ==> Both exons and introns
B-generally absent from bacterial genomes ==> Introns
C-part of the final mRNA strand ==> Exons
D-code for an amino acid sequence ==> Exons
E-removed from initial mRNA strand prior to translation ==> Introns
F-present in the DNA used as the template for transcription ==> Both exons and introns
In the genes of eukaryotic organisms, the exons are the segments of an RNA precursor that are conserved in the RNA after splicing and that are found in mature RNA in the cytoplasm. The segments of the RNA precursor that are removed during splicing are called in opposition to introns. Exons are mainly found in messenger RNAs (mRNAs) encoding proteins. Some mRNAs may sometimes undergo an alternative splicing process in which one or more exons may be excised or some introns preserved in rare cases.
This would <span>be caused</span> by a reversal of the temperature in the troposphere<span> (the region of the atmosphere nearest the Earth's surface), in which a layer of cool air at the surface is overlain by a layer of warmer air.</span>
An enzyme is a catalyst which means it changes the speed at which a chemical reaction occurs. It never alters the reaction in any way or changes nay chemical properties, only the speed at which it occurs and is completely absorbed in the meantime. The substrates that are reacting just have their reaction faster.
