DNA is a deoxyribonucleic acid, which is a hereditary material in all the organisms and is responsible for carrying hereditary characteristic features from one generation to another. The information stored in the DNA is in the form of a code made up of four chemical bases: Adenine (A), Guanine (G), Cytosine (C) and Thymine (T). The order, or sequence, of these bases determines the information available for building and maintaining an organism. These codes are known as base pairs which are attached to a sugar molecule and a phosphate molecule.
As we all know that life giving genetic code has four natural base pairs and they pair up to form two base pairs which are arranged in two long strands in the form of a ladder, a spiral structure called double helix and simply they are rearranged to create life from bacteria to humans.
Scientists of the Scripps Research Institute (TSRI), have discovered the first stable semi-synthetic organism, i.e. a single celled bacterium that may be important for the discovery of drugs or medicines and other applications.
It is an organism that relies on a man-made part to function as a part of its essential biology.
Scientists of TSRI, created a new bacterium that has all four natural bases (A, T, C and G) which every living organism have but also have two pairs of synthetic bases X and Y in its genetic code and it was said that if the semi-synthetic organism is really be an organism, then it will stably maintain the information by dropping X and Y base pair, as the additional information was used by the organism possessed in their DNA.
For this they have optimized a tool known as nucleotide transporter, which brings the necessary material for the unnatural base pair copied across the cell membrane. With the help of this it becomes easier for the organism to grow and divide while holding on to X and Y. Then copying the synthetic base pair becomes easy for the scientists by optimizing the previous version of Y. During DNA replication, creating a different molecule that can be better recognised by the enzymes that synthesise DNA molecules.
Then a new gene editing tool CRISPR-Cas9 is used by the researchers in such a way to see a genetic sequence in an organism without X and Y as a foreign invader. With the help of this a cell that dropped X and Y would be marked for destruction and can hold for new bases by the scientists.
Amazing is that the semi-synthetic organism was able to keep X and Y in its genome after dividing 60 times, which make scientists to believe that it can hold on to the base pair indefinitely.
In 1953 James Watson and Francis Crick had discovered the structure of DNA and told that function of DNA depends upon its structure only.
DNA is a long chain of polymers made from repeating units called nucleotides. There are four nucleotide monomers as mentioned above in the article they are A, T, G and C. These four nucleotides are made by sticking a phosphate group and a nucleobase to a sugar. This sugar is called deoxyribose. It is present in the form of rings containing one oxygen and four carbons and also contains a hydroxyl group (OH) attached to a third carbon in a ring.
These four monomers are distinguished by nucleobase and are also known as nitrogenous base.
A for Adenine, T for thymine, C for Cytosine and G for Guanine.
In DNA polymers phosphodiester bonds that join one DNA nucleotide to another are always link 5th carbon of the first nucleotide to the 3rd carbon of second nucleotide. And as a result covalent bond is formed. As shown below:
Now chromosomal DNA consists of two polymers of DNA, which make 3D structure called double helix. In this structure strands of DNA runs antiparallel i.e. 5th end of one DNA strand is parallel with a 3rd strand of other DNA. Something like this as shown below:
Each DNA strand formed by nucleotides is connected by non covalent bonds called hydrogen bonds.
Adenine (A) and Thymine (T) pair together as each have one donor and one acceptor whereas Cytosine (C) has one donor and two acceptor and Guanine (G) has one acceptor and two donor’s pair with each other.
- Polymers of DNA direct the production of other polymers called Proteins.
- A chromosome consists of smaller segments called genes. And each gene is divided in to three nucleotide sub segments called codons.
At last we can say that DNA is the information molecule which stores instructions to form large molecules called proteins. And these instructions are stored in each cell and distributed among 46 long structures called chromosomes. These chromosomes are made up of small segments of DNA called genes. The transmission of genes to an organism’s offspring is the basis of the inheritance of phenotypic traits or it forms organism which is like a parent organism like a man gave birth to a man, lion to a lion and so on. Gene also regulates the growth of an organism i.e. from puberty to adulthood to old age and death. It is also responsible to give specific characters to the individual like colour of eyes, colour of skin, determination of sex etc.
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