Question

3.) Vitamin C is an essential dietary vitamin for us because we cannot make it in our own bodies, the way that most animals can. This is because an important gene was inactivated by mutation in one of our ancestors millions of years ago. But vitamin C is not a protein. How can there be a gene to code for a molecule that is not a protein?

4.) RNA polymerase is the enzyme that reads a DNA sequence and “writes it” into a new RNA molecule. Most of our genome is NOT genes, though. How does RNA polymerase know where to find genes and start transcribingthem?

Answer 1

3). Vitamins are organic compounds which have to be obtained from the diet, either because an organism does not have the enzymes necessary to synthesize them or because it cannot produce them in sufficient quantities

All cases so far studied, the inability to synthesize vitamin C is due to mutations in the L-gulono-γ-lactone oxidase (GLO) gene which codes for the enzyme responsible for catalyzing the last step of vitamin C biosynthesis. ... This suggests that losing the ability to make vitamin C is a neutral trait.

In molecular terms, a gene is the entire DNA sequence required for synthesis of a functional protein or RNA molecule. ... Although the majority of genes encode proteins,but there are some genes that encodes for tRNAs, rRNAs, and other types of RNA

4).A RNA polymerase (RNAP), or ribonucleic acid polymerase, is a multi subunit enzyme that catalyzes the process of transcription where an RNA polymer is synthesized from a DNA template.Signals in DNA indicate to RNA polymerase where it should start and end transcription. These signals are special sequences in DNA that are recognized by the RNA polymerase or by proteins that help RNA polymerase determine where it should bind the DNA to start transcription. A DNA sequence at which the RNA polymerase binds to start transcription is called a promoter.

Prokaryotic RNA polymerases have 2 components, a core enzyme and a sigma factor (a.ka. sigma subunit).

The sigma factor is necessary for the RNA polymerase to bind tightly to the promoter and initiate transcription.

Once transcription starts, the sigma factor falls off, and the core enzyme continues copying the DNA into RNA till it reaches a terminator. A terminator is a sequence of DNA that signals RNA polymerase to stop transcribing.