DNA, Genetics, and Key Medical Diagnostic Techniques

Core Biological Concepts: Nucleic Acids and Genetics

Nucleic Acids: Composition and Structure

Biomolecules such as Nucleic Acids are critical for living organisms. They are composed of carbon, hydrogen, nitrogen, phosphorus, and oxygen. They are also called polynucleotides because they are formed by the joining of subunits called nucleotides. Each nucleotide is made of:

• A sugar (with 5 carbon atoms)
• A molecule of phosphoric acid
• A nitrogenous base

DNA Structure and Function

DNA (Deoxyribonucleic Acid) is a macromolecule consisting of two long chains of nucleotides, known as complementary strands, shaped like a double helix. The structure maintains its stability due to the nitrogenous bases, which are located in the center of the helix and joined by hydrogen bonds.

Functions of DNA

DNA performs three essential functions:

• It stores the genetic information in the cell.
• It governs all cellular activity.
• It transmits genetic information from generation to generation.

Chromatin and Chromosomes

Chromatin is present in the interphase nucleus and corresponds to nucleosome fibers tied together by the DNA double helix. Chromosomes are condensed structures present in the nucleus during cell division.

Somatic cells contain 23 pairs of chromosomes (46 total), while gametes contain half that number (23). Chromosomes are called homologous pairs, and the somatic cell number is diploid (2n). Gametes are haploid (n).

Gene Expression: Transcription and Translation

Transcription is the process by which the genetic message contained in DNA is transmitted to messenger RNA (mRNA). The mRNA is produced using one of the two DNA strands as a template.

Translation is the process by which a protein is manufactured from the information contained in the mRNA.

Medical Imaging and Clinical Procedures

Radiology and Radiotherapy

Diagnostic Radiology is a medical specialty employing different physical agents, such as X-rays, to generate images inside the body for diagnosis, prognosis, and treatment of diseases. It focuses primarily on diagnosing diseases through images.

There is also Interventional Radiology, which focuses on the treatment of disease through surgical procedures guided by imaging techniques.

Radiation Therapy (Radiotherapy) does not primarily use images but employs ionizing radiation (including X-radiation) for therapeutic purposes.

Diagnostic Ultrasound

Diagnostic ultrasound imaging uses high-frequency sound waves. A small instrument called a transducer or probe emits ultrasound waves into the body area being studied. The transducer collects the reflection or echo of the sound waves passing through different structures.

The echoes have different amplitudes according to the organs traversed. The transducer and a computer convert these echoes into images that analyze the size, shape, and content of the scanned anatomical structure.

Transplantation Challenges

Transplantation procedures face several critical problems:

• Rejection: When the donor and recipient are not genetically identical, the recipient's immune system recognizes the organ as foreign, producing a response against it and attempting to destroy it.
• Disease Transmission: Viral diseases or other illnesses can be transmitted by transplantation if the donated organ or tissue is infected.