The groundbreaking “long-read” sequencing technique, a recent innovation in the field of genetics has delivered high-quality and trustworthy sequence from one end of the Y chromosome to another. These impressive results were presented in the Nature Journal, providing an insightful look into sex genes’ functionality, sperm details, the evolution of the Y chromosome, and its potential extinction in several million years.
Previously conducted research has thrown light on the critical role of the Y chromosome in colorectal and bladder cancers. These studies unveiled crucial genetic mechanisms responsible for tumor progression, immune response, and clinical prognosis.
DNA, Gene, and Chromosomes: The Fundamental Units of Genetics
Fundamental to our understanding of genetics are three basic building blocks: DNA, genes, and chromosomes. DNA represents our unique genetic makeup in the form of a long molecule. It takes the double helix shape, reminiscent of a spiral staircase, with two strands wrapping around each other. Four basic building blocks or ‘bases’ constitute each strand of DNA: adenine (A), cytosine (C), guanine (G), and thymine (T).
Genes are segments of DNA responsible for the production of particular molecules within the body, typically proteins. These proteins control how the body functions and grows. Genes play a significant role in determining physical characteristics like eye color, blood type, and height. Every cell has two sets of genes—one that came from your mother and another from your father.
Furthermore, to maintain order, these genes are divided into 46 parcels known as chromosomes. Chromosomes are thread-like structures in the nucleus of each cell wherein the DNA molecule is packaged. Chromosomes comprise DNA coiled multiple times around supporting proteins called histones.
The Y Chromosome: Discovery and Significance
The male-determining Y chromosome carries a gene called SRY (Sex-Determining Region Y), crucial for the development of testis in embryos. Y differs significantly from its sister chromosome X and the remaining 22 chromosomes of the human genome in terms of size and DNA sequences. Its massive amounts of seemingly non-contributory DNA sequences (often referred to as “junk DNA”) have made it a challenge to sequence this chromosome.
Around 150 million years ago, the SRY evolved, resulting in a rapidly degenerating proto-Y that lost around 10 active genes per million years. If this trend continues, the Y chromosome could vanish in a few million years, similar to its disappearance in certain rodents.
The sequencing of Y has uncovered some remarkable findings. The sequencing method used is known as T2T (telomere-to-telomere). Telomeres are structures comprising DNA sequences and proteins found at chromosomes’ ends. While some newly discovered genes were merely extra copies of known ones, the centromere structure is now known, and the repetitive sequences at the Y’s end have been read.
Understanding Long Read Sequencing
Long-read sequencing, also referred to as third-generation sequencing, is a DNA sequencing technique capable of sequencing much longer DNA fragments than traditional short-read sequencing methods. One of the most basic forms of DNA sequencing is Sanger sequencing, which can sequence small fragments of DNA (up to 900 base pairs).
However, modern DNA sequencing methods, known as next-generation sequencing, can efficiently determine longer DNA sequences compared to Sanger sequencing. Over the past decade, long-read, single-molecule DNA sequencing technologies have emerged as powerful tools in genomics. While short reads capture the majority of genetic variations, long-read sequencing can detect complex structural variants that might be challenging to identify with short reads.
Previous Year Questions on UPSC Civil Services Examination
In the 2019 UPSC Civil Services Examination, a question was asked about the Cas9 protein, a molecular scissors used in targeted gene editing. In 2017, the role of genome sequencing in agriculture was tested. The technique can be used to identify genetic markers for disease resistance and drought tolerance in various crops, speeding up the development of new crop varieties and deciphering host-pathogen relationships in crops.
Research and Development Achievements in Applied Biotechnology
Applied biotechnology has led to several research and development achievements. These advancements are expected to significantly uplift the poorer sections of society by improving agriculture, developing new treatments for diseases, and creating sustainable ways to produce energy.