The correct answer is Transcription. Transcription is the process of copying DNA to mRNA and is the first step of protein biosynthesis.

A promotor may be described as a sequence of bases at which RNA polymerase begins transcription. Once the RNA polymerase - sigma factor complex recognizes the promoter sequence, the sigma factor dissociates from RNA polymerase which unwinds the DNA helix thus exposing a template for transcription.

The correct answer is cistron. Note that the terms cistron and gene are approximately the same. A gene could have several cistrons but this is unusual.

Constitutive genes are expressed under all circumstances by a cell or organism, regardless of environmental influences.

Repressor proteins bind to DNA in such a way that they interfere with RNA Polymerase action and prevent gene expression. This is a form of negative control on protein synthesis. Hence, the activity of specific proteins within cells is regulated through either blocks or enhancement of RNA polymerase action at the level of transcription. Also, genes whose expression can be controlled by external factors are called regulatable genes.

For rho-independent termination, there is a G-C-rich stretch of nucleotides, followed by an A-T-rich stretch of nucleotides. When this stretch is transcribed into RNA, the sequence of the nucleotides is such that the RNA molecule forms a short double-stranded region called a hairpin which significantly slows down RNA polymerase causing it to pause in the A-T-rich region. Because the A-T rich region is relatively unstable, the transcription complex falls apart, ending transcription.

Bacterial promoters usually contain two important DNA sequences that are involved in the regulation of transcription :
1) TATAAT at the -10 position.
2) TTGACA at the -35 position.
Both sequences are upstream of the actual gene...The –10 sequence is also known as the Pribnow box, in honor of its discoverer.

Introns are sections of DNA within a gene that do not encode part of the protein that the gene produces. They are spliced out of the mRNA that is transcribed from the gene before it is exported from the cell nucleus. The regions of a gene that remain in the spliced mRNA are called Exons. Introns allow for alternative splicing of a gene, so that several different proteins that share some common DNA sections can be produced from a single gene.

RNA with enzymatic activity, (for example - self-splicing RNA) are called ribozymes. Note that the functional part of the ribosome (the protein translator), is a ribozyme.

The transcribed mRNA includes several introns and exons. But what is an intron and what is an exon is not decided yet. This decision is made during the splicing process. The result of alternative splicing is that information can be stored much more economically. Several proteins can be encoded in a DNA sequence whose length would only be enough for two proteins. The regulation of the splicing process is still widely unknown...

Pseudogenes are inactive sequences of genomic DNA which have a similar sequence to known functional genes and are considered to be evolutionary relatives to normally functioning genes.

Most mRNAs have their starting end blocked by the addition of a cap (7-methylguanosine) which has no free phosphates. As a result it is protected from attack by phosphatases, or nucleases. It also helps ribosomes attach for translation.

A codon is a three nucleotide sequence which codes for the insertion of a unique amino acid during translation. As an example, UCU specifies the amino acid serine.

The poly A tail which is usually 20 to 200 nucleotides is not encoded by the gene but is added post-transcriptionally. It is is thought to confer stability to the mRNA. The addition of the poly-A-tail is called RNA polyadenylation.

An Operon is a collection of multiple structural genes so that they are transcribed as a single mRNA. Operons found primarily in prokaryotes and nematodes were first described by Francois Jacob and Jacques Monod in 1961. They allow cells to respond to their environment.

A DNA-binding protein in prokaryotes that prevents the transcription of a gene by binding to the operator region is called a Repressor. For example : The lac repressor protein prevents the expression of the lac Operon which governs the production of enzymes for metabolizing lactose.

The lac repressor stops the metabolism of lactose in bacteria as long as glucose is available. However, when lactose is plentiful and glucose is scarce, the lac repressor becomes inactive. This allows the conversion of lactose to glucose.

A RNA sequence that is complementary to the mRNA of a particular gene will prevent the translation of that gene into a protein by binding to the mRNA of that gene. This may be a defense mechanism against viruses which can use double-stranded mRNA as an intermediate.

A Gene that is transcribed into RNA which in turn is not translated into a protein is called an RNA gene or non-coding RNA (ncRNA) or functional RNA (fRNA). Examples are : Transfer RNA (tRNA) and Ribosomal RNA (rRNA), both of which are involved in the process of translation.

For the transcribed RNA sequence, base pairs are : A - U and G - C.