A process of mRNA synthesis.

What is mRNA? How it is made? For what function it stands for? In the given

essay all this questions will be answered. First, mRNA is a long chain of polynucleotide

chain sequence, which forms from nucleotides (Boyle, 2002). Nucleotides is a molecule

with tree phosphate group, with one sugar and with one base pair (Boyle, 2002).

Nucleotide is connecting with another by phosphodiester group (Boyle, 2002).

What is the Function of mRNA?

Function of mRNA is essential for the cell proper function. This is because

mRNA is used as a template to do an amino acids sequence, which then transform to the

protein (Scott, 2008). So, mRNA gives a signal to make specific kind of protein. This

function can be carried only by mRNA, because for other molecules it would be difficult

to leave nuclear membrane through the nuclear pores to cytosol inside the cell.  For that

reason, mRNA is called messenger RNA (Scott, 2008).

From gene to mRNA.

Gene consists of DNA, main function of DNA is storage of information and it

consists of double strands (Scott, 2008). These two strands wrap around each other and

form double helix (Scott, 2008). Information from one  DNA strand can be used to

produce mRNA strands. Even if mRNA is made by coping one of DNA strands by using

another, it has one difference from it. DNA consist of thiamine, adenine, guanine,

cytosine bases, while mRNA has uracil base instead of thiamine in its strand (Scott,

2008). One mRNA is made in three stages, such as initiation, elongation and termination.

 Initiation:

In initiation is a process starts when part of DNA called promoter is

identified by polymerase (Boyle, 2002). Promoter is important, because it stands

before a piece of DNA which will be used as template for mRNA (Boyle, 2002).

Without promoter synthesis of mRNA will be impossible, since enzyme

polymerase will not be able to identify DNA part, which must be copied.  When

enzyme called polymerase identify promoter, it ready to start the process of

polynucleotide sequence and enzyme called helicase opens DNA strands (Boyle,

2002). But polymerase do not copy DNA immediately it is starts after 10

nucleotides it start synthesis of mRNA (Boyle, 2002).

 Elongation:

Elongation is a process of polynucleotide chain formation (Mike and

Kathryn, 2008). Polymerase is moving along the strands of DNA and makes copy

of only one of the strands (Mike and Kathryn, 2008). Usually is a strand with

direction 5’ 3’. This is because energy required for making a phosphodiester

bond between two nucleotides can be found only in 5’ 3 direction (Mike and

Kathryn, 2008). It is possible to identify 5’ end from 3’ end nucleotide sequence,

because 5’ and has phosphate group at the end, while 3’ end has hydrohyl group

at the end. Phosphate group is molecule with formula PO42-, while hydroxyl has

formula OH (Mike and Kathryn, 2008). During the elongation process,

polymerase makes copy one of DNA strands by using another as a template.

 Termination:

Termination is the last process of mRNA synthesis. It starts when enzyme

called mRNA polymerase II achieve a signal called polyadenylation signal (Scott,

2008). It signals appear when polymerase II reaches a certain sequence of DNA

(Scott, 2008).  After that, polymerase stops coping DNA strand and release

mRNA.

References:

Boyle M., Biology, Collins advanced science, 2002.

Mike B. and Kathryn S., Human Biology, Advanced science, 2008.

Scott F., Biological Science, Pearson, 2008.