Context:
Researchers have identified around 500 Ultra-conserved elements (UCEs) in the genomes of humans, rats, and mice that have remained unchanged for 80 million years since their last common ancestor.
Ultra-Conserved Elements (UCEs)
- UCEs: Stretches of DNA highly conserved across different species
- Discovered: 2004 by comparing genomes of humans, mice, and rats
- Definition: At least 200 base pairs long, 100% sequence identity across species
- Location: Found in both coding and non-coding regions of the genome
Key Characteristics
- Found near genes involved in development and regulation
- Do not tolerate mutations: Remain identical across species for tens of millions of years
- Many do not code for proteins but are crucial for gene regulation and cellular function
- Evolutionary Significance: Present in multiple lineages, useful for phylogenetic studies and comparative genomics
- Genomic Locations: Found in introns, intergenic regions, and within protein-coding genes
Applications of UCEs
- Phylogenetics & Systematics: Powerful markers for reconstructing evolutionary relationships between species
- Comparative Genomics: Reveal conserved regulatory elements and potential functions
- Human Disease Research: Linked to essential biological processes, roles in disease susceptibility
Regulation of Protein Levels by UCEs
- UCE in Tra2b gene (mice): Crucial for controlling Tra2β protein production
- Deletion of UCE: Causes overproduction of Tra2β, death of sperm-producing cells, infertility
- Mutation Impact: Disrupts function, prevents mouse reproduction
Tra2b Gene – RNA Splicing – UCEs
- Tra2b (Transformer-2 beta) gene: Encodes Tra2β protein, key regulator of RNA splicing
- RNA splicing: Process by which introns are removed and exons joined to form mature mRNA
- Role in RNA Splicing
- Tra2β protein: Regulates alternative splicing, ensures correct mRNA variants for different cell types and conditions
- Important in tissues requiring precise splicing control: testes, brain, embryonic cells
- Connection to UCEs
- UCE in Tra2b gene: Embedded in first intron, highly conserved
- Function of UCE: Acts as a poison exon, prevents excessive production of Tra2β protein
Overlap Between Human and Mouse Genomes
- Common Ancestor: Humans and mice share a mammalian ancestor from 80 million years ago
Genomic Similarity
- 85% of mouse genes: Have direct counterparts in humans
- Nearly 500 UCEs: Identical between humans and mice despite millions of years of evolution
- Fundamental processes: Cell division, metabolism, brain function are similar, requiring conservation of crucial DNA regions
Medical Research
- Model organism: Mice are used to study human genetics, diseases, drug responses due to genomic similarities
- UCEs: Help scientists understand gene function across species, providing insights into evolution and biomedical advancements
Source: The Hindu
Previous Year Question
Recombinant DNA technology (Genetic Engineering) allows genes to be transferred
1. across different species of plants
2. from animals to plants
3. from microorganisms to higher organisms
Select the correct answer using the codes given below.
[UPSC CSE – 2013 Prelims]
(a) 1 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3
Answer: (d)