DNA

    "What is DNA?"

• The DNA backbone and the structure of the helix:

DNA is a composite molecule consisting of two very long strands that interlace to give rise to a double helix form. Each strand consists of smaller units of molecules referred to as nucleotides. A Nucleotide comprises of three parts:

1.Phosphate group: 

A phosphorus atom connected to four oxygen atoms.

2.Deoxyribose sugar: 

A five carbon-containing sugar molecule that assists as a backbone.

3.Nitrogenous base: 

In RNA, there are four kinds of nitrogenous bases. These are.

Adenine, symbol A

Thymine, symbol T

Cytosine, symbol C

Guanine, symbol G

The order of these bases in the DNA strand is what determines the genetic code. The bases on the two strands bind together in the following way:

Adenine with Thymine (A-T)

Cytosine with Guanine (C-G)

The pairings are stabilized by hydrogen bonds that are weaker than the covalent bonds that hold the sugar phosphate backbone together, though it is strong enough to keep the strands connected. That means the structure of DNA which is double helical is very stable and hence great amounts of information can be stored in the DNA.

•DNA as Genetic Code:

In the case of DNA, information is contained in the nitrogen base sequences. Codons are the three base sequences that take after each other on a nucleotide strand of DNA. Each of the codons also corresponds to a single amino acid. Cells contain proteins that play a variety of roles, and one of them is the amino acid which makes up the proteins. Most of the cellular activity in the living cells is facilitated by proteins such as the chemical processes called metabolism, fixing the damaged parts of cells, and communication within the cell and with other cells.

An organism's genome refers to the complete encasement of DNA within that particular organism and contains all of the information necessary to make all of the proteins that organism requires. In human beings, the genome comprises 23 paired chromosomes that are found in the nucleus of the cell. A chromosome is a long molecular macromolecule consisting of coiled D.N.A.

•DNA Replication:

DNA has this extraordinary property whereby it can create copies of itself, and such properties are crucial for cell division as well as reproduction. During the cell division process, it is required that each newly formed cell should contain identical copies of DNA. The replication of DNA involves the steps listed below: 

The double helix structure of D.N.A. unzips and opens to give rise to two single strands.

Templates are formed by each of the strands for the synthesis of a new associated strand.

Specialized enzymes such as DNA polymerase join in the appropriate nucleotides to the unpaired bases on each of the existing strand.

As a result, there are two similar DNA molecules produced, each containing one of the original strands and one of the newly synthesized strands. This procedure is referred to as semi-conservative replication since each new molecule of DNA made retains on of the original stand.

•DNA transcription and Translation:

The DNA is not for producing proteins, it ned’s some in between help and that way it acts as a precursor for Messenger RNA (mRNA) synthesis in a process referred to as transcription, which occurs when:

The DNA strand gets separated spirally in the section with the gene of interest.

A certain enzyme called RNA polymerase synthesizes the mRNA strand by adding RNA nucleotides complementary to the available bases on the DNA.

In addition, while DNA contains thymine (T), RNA consists of uracil (U) instead of the corresponding base thymine. This means that in the case of mRNA, A will instead pair with U.

Once mRNA has been synthesized, it exits the nucleus and makes its way to a ribosome situated in the cytoplasm of the cell, the region where translation takes place. In translation:

The sequence of nucleotides in the mRNA is taken in ‘chunks’ of three bases known as codons.

Every codon corresponds to a specific amino acid which is delivered to the ribosome by the transfer RNA or tRNA.

Then ribosome joints all these amino acids to make a chain termed polypeptide chain which undergoes folding to become a functional protein.

This entire process of transforming DNA information into actual proteins is referred to as gene expression.

•Role of DNA in Inheritance:

It is because DNA is the genetic material that inheritance of traits is possible. In the course of reproduction, an organism is able to pass a genetic blueprint in the form of DNA to its children, and that is the reason why one resembles the other. In the process of sexual reproduction, parental units provide half of their genetic material resulting to offspring with genetic variations.

The chromosomes of every organism are arranged in sets of two (i.e. one maternal and one paternal). Chromosomes contain information in the form of genes, which occur in different forms, known as alleles. The alleles that an individual receives determine his or her characteristics, such as the color of eyes, blood group and resistance to certain diseases.

•Mutations in DNA:

Mutation is a term that describes any alteration of a given DNA sequence. Mutations may occur for many reasons; for example, through mistakes during DNA replication, exposure to x-rays, or chemicals found in the environment. While some mutations might have no noticeable effects, others have the potential of giving rise to genetic disorders or predisposition to tumor development, such as cancer. Nevertheless, mutation contributes to genetic variations which is crucial in the process of evolution.

Point mutations: 

A change that affects only one nucleotide.

Insertions or deletions: 

The addition or loss of segments of DNA which may lead to frame shifts.

Chromosomal mutations:

Alterations on a large scale including the addition of a piece of chromosome or the turning around of a segment of chromosome.

Changes in genetic material that take place in the reproductive cell also known as germ cell can be inherited by the offspring while the mutations occurring in somatic cells only influence the individual.

•Significance of DNA in Evolution:

Without a doubt, DNA contributes to the evolution theory. The reason DNA synthesis is error-prone thus mutations are tolerated. These successive modifications in the DNA of the organism will undoubtedly provide different types of organisms that in the course of their existence, will face harsh conditions of nature, and natural selection will cause them to change over time. species – new species will appear. This is the ground for biological richness and further processes of species development.

Evolutionary biology has benefited from the invention of DNA sequencing as it made it possible to examine the DNA amongst different organisms and the relationships they have in terms of evolution. For example, more than 98 of human DNA is similar to that of a chimp which is evidence of evolutionary kinship.

•Relevance of DNA Knowledge:

Advanced studies of DNA have changed how we view living organisms and treat diseases:

*Genetic Engineering: 

This has made it possible for scientists to modify the DNA of organisms in order to optimize desirable characteristics or produce drugs. For instance, bacteria that have been genetically modified to produce insulin for people suffering from diabetes.

*Gene Therapy: 

These are research-based procedures that include injecting healthy genes in a patient to replace abnormal or defective ones.

*Forensic science: 

Through DNA fingerprints, individuals can be located with minimal margins of errors.

*Personalized Medicine: 

Those treatments that are based on the DNA may be effective because of the specific genetics of a person.

*Evolutionary Studies: 

Through the use of DNA, evolution can be reconstructed, and how certain characters were acquired can be explained genetically.

•Ethics and Controversies:

DNA research encompasses complex ethical issues, particularly when it comes to genetic engineering, reproductive techniques, or privacy of individuals. Taking these mitigating measures into account, one can still argue that making genetic modifications to humans may have unforeseeable consequences. With regards to the process of cloning as made available today, issues of personality and identity come into focus. Furthermore, as the circle of individuals who can possess a person’s genetic material widens, issues of privacy and potential abuse of such materials come into play.

•In Brief:

DNA is the organic substance containing genetic information in every living cell and serves as a framework for all types of organisms to develop, function and reproduce. It is made in the shape of double helix for the purpose of sustaining accurate replication and storage of information for protein synthesis. 

Transmission and variability of genetic information are the processes that ensure evolution of life and its biological diversity on the planet Earth, therefore the development of tools based on DNA has been an amazing driver of progress in various areas including medicine, genetics, and, most importantly, evolutionary biology and its study of history.