Please describe the making of an m(messenger)RNA?

Question

please i need help understanding

Answer 1

Well basically, it's like the DNA is double stranded. The strand unravels a bit to show the 'insides' of the DNA.

So the DNA like gets exposed a bit and and enzymes can then make a corresponding mRNA from the 'exposed' bits.

This process is called transcription

You can see a diagram of it here:
http://microvet.arizona.edu/Courses/vsc610/MIC205/transcription.jpg

http://publications.nigms.nih.gov/chemhealth/images/chapter1_rna.gif

Answer 2

The long answer above comes from www.wikipedia.org. You will find all the pictures there etc.

Short answer is that a protein called RNA polymerase transcribes the DNA into the mRNA. It's almost an exact copy of one of the strings (called the "sense" string), however Thymine is exchanged with Uracile.

Answer 3

Messenger Ribonucleic Acid (mRNA) is RNA that encodes and carries information from DNA during transcription to sites of protein synthesis to undergo translation in order to yield a gene product.

The brief life of a mRNA molecule begins with transcription and ultimately ends in degradation. During its life, an mRNA molecule may also be processed, edited, and transported prior to translation. Eukaryotic mRNA molecules often require extensive processing and transport, while prokaryotic molecules do not.

During transcription, RNA polymerase makes a copy of a gene from the DNA to mRNA as needed. This process is similar in eukaryotes and prokaryotes. One notable difference, however, is that eukaryotic RNA polymerase associates with mRNA processing enzymes during transcription so that processing can proceed quickly after the start of transcription. The short-lived, unprocessed or partially processed, product is termed pre-mRNA; once completely processed, it is termed mature mRNA.

Processing of mRNA differs greatly between eukaryotes and prokaryotes. Prokaryotic mRNA is essentially mature upon transcription and requires no processing, except in rare cases. Eukaryotic pre-mRNA, however, requires extensive processing.

Splicing is the process by which pre-mRNA is modified to remove certain stretches of non-coding sequences called introns; the stretches that remain include protein-coding sequences and are called exons. Sometimes pre-mRNA messages may be spliced in several different ways, allowing a single gene to encode multiple proteins. This process is called alternative splicing. Splicing is usually performed by an RNA-protein complex called the spliceosome, but some RNA molecules are also capable of catalyzing their own splicing (see ribozymes).

The 5' cap is modified guanine nucleotide is added to the "front" (5' end) of the pre-mRNA using a 5',5-Triphosphate linkage. This modification is critical for recognition and proper attachment of mRNA to the ribosome, as well as protection from 5' exonucleases. It may also be important for other essential processes, such as splicing and transport.

Polyadenylation is the covalent linkage of a polyadenylyl moiety to a messenger RNA molecule. In eukaryotic organisms, polyadenylation is the mechanism by which most messenger RNA (mRNA) molecules are terminated at their 3' ends. The poly(A) tail aids in mRNA stability by protecting it from exonucleases. Polyadenylation is also important for transcription termination, export of the mRNA from the nucleus, and translation. Some prokaryotic mRNAs also are polyadenylated, although the poly(A) tail's function is different from that in eukaryotes.

Polyadenylation occurs during and immediately after transcription of DNA into RNA. After transcription has been terminated, the mRNA chain is cleaved through the action of an endonuclease complex associated with RNA polymerase. The cleavage site is characterized by the presence of the base sequence AAUAAA near the cleavage site. After the mRNA has been cleaved, 80 to 250 adenosine residues are added to the free 3' end at the cleavage site. This reaction is catalyzed by polyadenylate polymerase.l

In some instances, an mRNA will be edited, changing the nucleotide composition of that mRNA. An example in humans is the apolipoprotein B mRNA, which is edited in some tissues, but not others. The editing creates an early stop codon, which upon translation, produces a shorter protein.

Another difference between eukaryotes and prokaryotes is mRNA transport. Because eukaryotic transcription and translation is compartmentally separated, eukaryotic mRNAs must be exported from the nucleus to the cytoplasm. Mature mRNAs are recognized by their processed modifications and then exported through the nuclear pore.

Because prokaryotic mRNA does not need to be processed or transported, translation by the ribosome can begin immediately after the start of transcription. Therefore, it can be said that prokaryotic translation is coupled to transcription and occurs co-transcriptionally.

Eukaryotic mRNA that has been processed and transported to the cytoplasm (i.e. mature mRNA) can then be translated by the ribosome. Translation may occur at ribosomes free-floating in the cytoplasm, or directed to the endoplasmic reticulum by the signal recognition particle. Therefore, unlike prokaryotes, eukaryotic translation is not directly coupled to transcription.

After a certain amount of time, the message is degraded into its component nucleotides, usually with the assistance of RNases. The limited longevity of mRNA enables a cell to alter protein synthesis rapidly in response to its changing needs.

Different mRNAs within the same cell have distinct lifetimes. In bacterial cells, individual mRNAs can survive from seconds to more than an hour; in mammalian cells, mRNA lifetimes range from several minutes to days. The greater the stability of an mRNA, the more protein may be produced from that transcript. The presence of AUUUA motifs in some species of mRNA tends to destabilize the transcript through the actions of intracellular binding proteins.