Question 4:
In 2014, scientists from the Scripps Research Institute, California, announced the development of 6 base DNA. A new base pair that they added to the standard 4 base (ATGC) DNA was called:
Scripps 6-Base DNA: X-Y Breakthrough Explained
In 2014, scientists at the Scripps Research Institute introduced a groundbreaking synthetic base pair to natural DNA, expanding it from four bases (A, T, G, C) to six. This X-Y pair marked a milestone in synthetic biology.
Correct Answer
The correct answer is (A) X-Y. Researchers led by Floyd Romesberg engineered two synthetic nucleotides, X and Y, forming a stable unnatural base pair. This pair replicated efficiently in E. coli cells, creating the first semi-synthetic organism with a six-letter genetic alphabet.
Option Breakdown
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(A) X-Y: Accurate designation for the added synthetic base pair from Scripps’ 2014 study, enabling DNA replication with expanded coding potential.
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(B) P-Q: Incorrect; no records link P-Q to Scripps’ work or any major six-base DNA project.
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(C) A-T**: Incorrect; asterisks denote modifications but Scripps used entirely new X and Y, not altered natural bases.
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(D) G-C**: Incorrect; similar to C, this implies tweaked natural pairs, not the novel orthogonal X-Y pair developed.
Breakthrough Impact
This innovation allows DNA to encode up to 152 new amino acids, opening doors to novel proteins for medicine and materials. By 2017, stable E. coli strains retained the X-Y pair across generations using CRISPR tweaks.
| Aspect | Natural DNA (4 bases) | Expanded DNA (6 bases) |
|---|---|---|
| Base Pairs | A-T, G-C | A-T, G-C, X-Y |
| Coding Capacity | 20 amino acids | 152+ unnatural amino acids |
| Applications | Standard biology | Synthetic proteins, therapeutics |
