Letter to Editor ( format , solved and unsolved example)

A letter to the editor is a letter sent to a publication about issues of concern from its readers.Here is an simple basic format to write a letter to editor.

Format
1. sender’s address
(e.g. CB-12A
          Shalimar Bagh
          Delhi, )
                                     
2. date
( e.g. 14 May , 2017 )
 3. receiver’s address
      ( e.g. The editor
                The Hindustan Times )
4. subject / heading
5. salutation,
      (e.g. sir / madam,)
complimentary close 1 mark
6. content ( Through the column of your esteemed paper I would like to draw attention to one of the gravest situation of these days ——————————————————————)
7. conclusion ( ———————————————————————————- )
Thanking you,
Signature
Name ( X,Y,Z)
Content 3 marks
 grammatical accuracy, appropriate words and spelling    [1]
 coherence and relevance of ideas and style                        [1]
2 marks

Here is an solved e.g.
Write a letter to the Editor of a newspaper against the use of unfair means by students in examinations. Your name is Ashok Goyal and you live at CB 12 A , Shalimar Bagh , New Delhi
CB 12 A
Shalimar Bagh
New Delhi
14 May, 2017
            The Editor,
            The Hindustan Times,
            New Delhi,
Dear Sir,
                           Through the column of your esteemed paper I would like to draw attention to one of the gravest situation of these days i.e. the use of unfair means by students in examinations. I shall feel highly obliges if you publish my views on the subject in your esteemed Daily.
            The use of unfair means by students has become very common. But the menace has assumed dangerous proportions now. Copying in examinations goes on unchecked. No wonder, here and there, some invigilators are found helping the examinees in the use of unfair means.  The evil has become deep-rooted.
The system of examination needs, complete overhauling.
            In fact, examinations have become a farce. They have lost their meaning. Among the reform in the examination system, introduction of internal assessment, setting of objective type questions and delinking of degrees can be suggested. The purpose of holding examination is to test the ability of the students. Any system of examinations that does not serve this end is purposeless. The sooner it is abolished the better it will be.
            I hope these views of mine will go a long way in making examinations meaningful.
Thanking you,
Yours faithfully,
Ashok Goyal.

Letter for practice :-

1.   Lack of job opportunities in rural area forcing people to migrate to cities. Every big city has a number of slum in this. Life in these slums is miserable. Write a letter to the editor of national newspaper on how we can improve the living conditions in these slums. You are Ashok / Radhika , CB 12 A, Shalimar Bagh , New Delhi

operon system ( lac operon )

Operon is the segment of DNA which transcribes the mRNA
Here lac refers to lactose.
Therefore lac operon is that segment of DNA transcribing the mRNA which is responsible for hydrolysis of the disaccharide, lactose into galactose.
The elucidation of the lac operon was also a result of a close association between a geneticist, Francois Jacob and a biochemist, Jacque Monod they were the first to elucidate a transcriptionally regulated system. In lac operon, polycistronic structural gene is regulated by a common promoter and regulatory genes. Such arrangement is very common in bacteria and is referred to an operon. Lac operon consists on one regulatory gene. One repressor gene (i) which codes for the repressor of the lac operon. It consists of three structural gene (z;y;a). The Z gene codes for beta galactosidase which is primarily responsible for the hydrolysis of the disaccharide, lactose into galactose. The Y gene codes for permease, which increase permeability of the cell to beta galactosidase. The A gene encodes for transacetylase.
 Here all three gene products are required for metabolism of lactose.

Functioning of lac operon :-
i. Inactive state of lac operon :-
In lac operon lactose is act as inducer. In the absence pf lactose repressor gene synthesise repressor as lactose is absent therefore the repressor binds with operator region and prevent the synthesis of RNA Polymerase. As RNA Polymerase has not be synthesised therefore the process of transcription stops.

ii. Active state of lac operon :-
In presence of an inducer i.e. lactose . Lactose binds with repressor synthesised by repressor gene and makes it inactive. As now operator region is free from repressor it can synthesise RNA Polymerase. RNA Polymerase binds with promoter region and process of transcription goes on.

Hence it may be noted after some time the functioning of lac operon stops. This is due to the fact that after some time all the lactose converts into glucose or galactose by the beta galactosidase. And as glucose or galactose cannot function as inducer the lac operon become inactive.

This regulation of an operon in presence of an repressor is known as negative regulation of an operon.

Transduction ( Harshey and chase experiment)

Transduction is a process by which foreign DNA is introduced into a cell by a virus or viral vector.

Transduction or  Hershey–Chase experiments were a series of experiments conducted in 1952 by Alfred Hershey and Martha Chase that helped to confirm that DNA is genetic material. DNA had been known to biologists since 1869,but many scientists still assumed at the time that proteins carried the information for inheritance because DNA appeared simpler than proteins. In their experiments, Hershey and Chase showed that when bacteriophages, which are composed of DNA and protein, infect bacteria, their DNA enters the host bacterial cell, but most of their protein does not.

Let us discuss this experiment briefly :-
Bacteriophage are bacterial viruses. T2 is bacteriophage which infects E.coli bacteria in human intestine. A.D Hershey and Martha Chose grew two culture of E.coli. one culture was supplied with radioactive sulphur . Sulphur get incorporated with sulphur containing amino acids. Other with radioactive phosphorus. Phosphorus get incorporated with nucleotide which form nucleic acid which form DNA. Each type of bacteriophage were now  introduced in separate cultures having normal unlabelled bacteria. After some time both cultures were shaken in blender at 104 rpm to remove empty phage plastids (ghost’s). The culture was then centrifuged. The heavier bacteria settled down in the form of pellet.

I. Bacteria with radioactive sulphur or protein:-
It was found that phage with labelled protein do not make the bacteria labelled. Instead radioactivity was restricticted to upper surface of solution which contain only empty phage plastids.

II. Bacteria with radioactive phosphorus or DNA:-
Shaking did not produce supernatant ( the liquid lying above a solid residue) of  empty capsids coats. Instead the bacteria become labelled showing DNA of the phage entered bacteria.
This makes clear that the DNA is the genetic material not protein.
 

After that to confirm this Experiment the radioactivity was also seen in the progeny of bacteriophage

The progeny of two bacteriophage was also tested for radio activity. It was seen that virus derived from parent with labelled protein do not show radio activity while progeny derived from labelled DNA show radio activity. Show that DNA is genetic material.

Related Posts:
Transformation

Transcription

Transcription is the first step of gene expression, in which a particular segment of DNA is copied into RNA (especially mRNA) by the enzyme RNA polymerase. Both DNA and RNA are nucleic acids, which use base pairs of nucleotides as a complementary language.

Transcriptional unit:-
A transcriptional unit in DNA is primarily defined by three regions :-

• A Promoter:-
  Promoter region is present at 3’ end of template strand and at 5’ end of coding strand. Sigma factor binds with promoter region to initiate the process of transcription. It is DNA sequence provide binding site for RNA polymerase.

• The structural Gene :-
 Structural gene is present at in between of terminator region and promoter region.

• A terminator:-
It is present at 5’ end of template strand or at 3 ‘ end of coding strand. Terminator Factor (rho factor) binds with terminator region to terminate the process of transcription.

The main three steps taking place in during transcription are:-
                 

1. Initiation :-
The first step in transcription is initiation, when the RNA polymerase         binds to the DNA at 5′ end of the gene at a specialized sequence called a promoter .The initiation factor (sigma factor)  initiates the process of transcription

2. Elongation :-
Once DNA strand unwind the process of elongation initiates. RNA polymerase catalyse the process of elongation. In this process new nucleotides are added to mRNA.

3. Termination :-
The last step of transcription in which terminator factor binds with the terminating region of transcriptional unit and terminates the process of termination.

Thera re two more complexities in eukaryotes :-

1. There are at least three types of RNA Polymerase which transcribes the mRNA.

 RNA Polymerase I:-It transcribes the rRNAs

 RNA Polymerase II :- transcribes hnRNA (heterogenous nuclear RNA). hnRNA is partially transcribed mRNA.

 RNA Polymerase III :- transcribes tRNA , 5srRNAs , snRNAs (small nuclear RNAs)

2. Post Transcriptional Processes: –

• Splicing :- Transcripts contain both functional exons  and non functional introns. Hence by the process of splicing introns are removed and exons are joined in a definite manner by enzyme DNA ligase ( known as biological gum). hnRNA undergoes two additional processes known as capping and tailing . 
• Capping :- In capping a nucleotide known as methyl guanosine triphosphate is added to 5’ end of hnRNA. 
• Tailing :-In tailing adenylate residues are added to template

Now the hnRNA is fully transcribed and known as mRNA that is transported out of nucleus for transcription.

       

Learning +
In some viruses known as ribo viruses there are RNA as genetic material. So in these viruses RNA is transcribed to DNA and further process takes place This process of transcribing RNA into DNA is known as Reverse Transcription and it takes place by an enzyme known as reverse transcriptase.