What is DNA? A complete guide for beginners

Have you ever wondered why we are the way we are? Why do we inherit our mother’s eyes or our father’s smile? The answer to these questions lies in a tiny, but incredibly powerful molecule: DNA.

DNA, or deoxyribonucleic acid, is like an instruction book that contains all the information necessary to build and maintain a living organism. From the color of our eyes to our predisposition to certain diseases, everything is encoded in our DNA. This molecule, present in almost all cells in our body, is made up of a double helix, like a spiral staircase, where each rung is made up of pairs of nitrogenous bases: adenine (A), thymine (T), cytosine (C ) and guanine (G).

Main characteristics of DNA:

• Double helix structure: It consists of two intertwined chains, forming a spiral.
• Basic components: Nucleotides formed by a phosphate group, a sugar (deoxyribose) and a nitrogenous base.
• Nitrogenous bases: Adenine (A), thymine (T), cytosine (C) and guanine (G), where A joins with T and C with G.

The structure of DNA

DNA, or deoxyribonucleic acid, has a double helix structure. This characteristic structure was elucidated by James Watson and Francis Crick in 1953. The DNA molecule is composed of:

1. Nucleotides: basic units consisting of a phosphate group, a deoxyribose sugar, and a nitrogenous base.
2. nitrogenous bases:
   • Adenine (A)
   • Thymine (T)
   • Cytosine (C)
   • Guanine (G)

Bases pair specifically, forming hydrogen bonds:

• A with T (two links)
• C with G (three links)

These antiparallel strands coil together to form the helix, stabilized by interactions between stacked bases.

Basic components of DNA

DNA, deoxyribonucleic acid, is made up of several fundamental elements:

1. Nucleotides: They are the basic units of DNA. Each nucleotide is made up of:
   • phosphate group
   • Deoxyribose sugar
   • nitrogenous base
2. nitrogenous bases: There are four types:
   • Adenine (A)
   • Thymine (T)
   • Cytosine (C)
   • Guanine (G)
3. Double helix: Two chains of nucleotides are coiled into a double helix structure, held together by hydrogen bonds between complementary bases. Base sequences determine genetic information.

Double helix and its discovery

DNA has a double helix structure, discovered by James Watson and Francis Crick in 1953. They used X-ray diffraction data obtained by Rosalind Franklin and Maurice Wilkins. The double helix consists of two chains of nucleotides, which twist around each other. Each chain has an alternating phosphate and sugar backbone, and paired nitrogenous bases between them. The bases adenine (A) and thymine (T) form one pair, while cytosine (C) and guanine (G) form another. This discovery was crucial to understanding DNA replication and function.

Function of DNA in living organisms

DNA plays a crucial role in the life of organisms. It acts as the main carrier of genetic information, which is inherited from generation to generation and directs the development, functioning and reproduction of all living beings. The main functions of DNA include:

• Storage of genetic information: Contains the necessary instructions for the growth and functioning of organisms.
• Replication: Ensures that each daughter cell receives an exact copy of the DNA during cell division.
• Gene expression: Encodes the synthesis of proteins, essential for biological and structural activities.

The genetic code

The genetic code is the set of rules that uses the information stored in DNA to be translated into proteins, essential for cellular functioning. This code is composed of:

• Codons: Trios of nucleotides in messenger RNA.
• Amino acids: Subunits that make up proteins.

Features of the genetic code

1. Universal: It is practically the same in all living beings.
2. Degenerate: Several codons can code for the same amino acid.
3. Specific: Each codon only codes for one amino acid.

These characteristics allow the precise and efficient synthesis of proteins, vital for life.

DNA and genetic inheritance

DNA contains the genetic information essential for the functioning and development of organisms. Genetic inheritance is transmitted from parents to children through genes. These are fragments of DNA that code for specific characteristics.

• Recessive and dominant genes: Characters can be influenced by dominant or recessive genes.
• Alleles: Variations of a gene that determine specific traits.
• Mutations: Changes in the DNA sequence that can cause genetic variations.
• Chromosomes: Structures that organize and package DNA.

Combinations of mother and father alleles define the unique genetic heritage of an individual.

Genetic mutations

Genetic mutations are changes in the nucleotide sequence of DNA. These alterations can be:

• Substitutions: one nucleotide is replaced by another.
• Deletions: deletion of one or more nucleotides.
• Insertions: addition of additional nucleotides.

Mutations can be:

1. Silent: do not affect the function of the protein.
2. wrong sense: they change an amino acid in the protein.
3. Nonsense: generate a premature stop signal.

Factors that cause mutations include radiation, chemicals, and errors during DNA replication. Mutations can be inherited or acquired.

DNA sequencing methods

Deoxyribonucleic acid sequencing methods are various techniques used to determine the order of nucleotides in a DNA molecule. Among the most common are:

• Sanger: Used mainly in the 1970s, it is the classic method that uses chain terminators.
• Next-Generation Sequencing (NGS): More advanced technologies such as Illumina and Roche 454 allow massively parallel sequencing.
• Third Generation Sequencing: Methods such as PacBio and Oxford Nanopore offer longer readings and real-time data.

These methods have revolutionized molecular biology and genetics.

Practical applications of the study of DNA

The study of DNA has numerous applications in various fields:

1. Personalized Medicine: Allows the development of treatments based on the individual genetic profile of each patient.
2. Disease Diagnosis: Facilitates early detection of genetic diseases and predispositions.
3. Forensic: Used in the identification of individuals in criminal investigations and paternity cases.
4. Agriculture: Improves the resistance and quality of crops through genetic modification.
5. Biotechnology: Leads to innovations in the creation of products and therapies.

Additionally, genetic research can reveal evolutionary relationships and biodiversity between species.

Ethics and privacy in the study of DNA

The study of DNA raises several ethical and privacy issues that deserve attention:

1. Informed consent:
   • Individuals must give clear consent before any DNA analysis is performed.
   • It is crucial to highlight possible risks and benefits.
2. Data usage:
   • Concern may arise about who has access to genetic information.
   • Companies must ensure that data is not used for unauthorized purposes.
3. Genetic discrimination:
   • There are risks of discrimination in insurance and employment based on genetic information.
   • Need for laws that protect against discrimination.
4. Data storage:
   • Secure methods for storing genetic data.
   • Clear policies on retention and deletion times.

Conclusions and future research

The current understanding of DNA has allowed numerous advances in various areas of science. However, there are still numerous aspects that require further research:

1. Epigenetics: Study of hereditary changes that do not involve alterations in the DNA sequence.
2. genetic engineering: Improve techniques for accurate and safe genome editing.
3. Comparative genomics: Comparison of DNA between different species to understand evolution.
4. human genetics: DNA research for personalized disease treatments.

Continued research in these fields promises to revolutionize the understanding of biology and medical applications, offering new opportunities for the future.

Ambientum Editorial