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2nd April 2022 (7 Topics)

Scientists publish first complete sequence of genome


Scientists have published the first complete, gapless sequence of a human genome, two decades after the Human Genome Project produced the first draft human genome sequence.


Why it matters?

  • A complete human genome makes it easier to study genetic variation between individuals or between populations.
  • A genome refers to all of the genetic material in an organism.
  • The human genome is mostly the same in all people, but a very small part of the DNA does vary between one individual and another.
  • By constructing a complete human genome, scientists can use it for reference while studying the genome of various individuals, which would help them understand which variations, if any, might be responsible for disease.

What was missing?

  • The genetic sequence made available in 2003 from the Human Genome Project, an international collaboration between 1990 and 2003, contained information from a region of the human genome known as the
    • Here, the chromosome is rich in genes, and the DNA encodes for protein.
  • The 8% that was left out was in the area called heterochromatin.
    • This is a smaller portion of the genome, and does not produce protein.
  • There were at least two key reasons why heterochromatin was given lower priority.
    • This part of the genome was thought to be “junk DNA”, because it had no clear function.
    • Besides, the euchromatin contained more genes that were simpler to sequence with the tools available at the time.
  • Now, the fully sequenced genome is the result of the efforts of a global collaboration called the Telomere-2-Telomere (T2T) project.
  • The invention of new methods of DNA sequencing and computational analysis helped complete the reading of the remaining 8% of the genome.

What’s in the 8%?

  • The new reference genome, called T2T-CHM13, includes highly repetitive DNA sequences found in and around the telomeres (structures at the ends of chromosomes) and the centromeres (at the middle section of each chromosome).
  • The new sequence also reveals long stretches of DNA that are duplicated in the genome and are known to play important roles in evolution and disease.

The future:

  • The T2T consortium used the now-complete genome sequence as a reference to discover more than 2 million additional variants in the human genome.
    • These studies provide more accurate information about the genomic variants within 622 medically relevant genes.
  • The complete sequence will be valuable for studies that aim to establish comprehensive views of human genomic variation.
    • Many research groups have already started using a pre-release version of the complete human genome sequence for their research.
  • The new T2T reference genome will complement the standard human reference genome, known as Genome Reference Consortium builds 38 (GRCh38), which originated from the Human Genome Project and has been updated since.


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