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Genome sequencing |
This article will explore genome sequencing, what is human Genome, and how the human genome sequenced by future techniques in 2023. The Human genome sequencing was completed by the telomere method, but a new sequencing method developed in 2023 chem-map which targets specific genome sequences developing drug therapies in the future.
Human Genome?
The human genome of a person consists of double-stranded
Deoxyribonucleic acid (DNA), a compound that consists of genetic constituents
of that organism that help to carry genetic information. DNA is composed of two
twisted strands. Each strand consists of
four chemical units known as nucleotides. Adenine, Guanine, Cytosine, and
Thymine. Both opposite strands pair with each other. Adenine makes a double bond
pairing with thymine and Cytosine makes triple bond pair with guanine
respectively.
Where does the word “Genome” come from?
The term
genome consists of two words gene and ome, meaning the whole set to denote the
entire DNA. Scientists are using this word that refers to hereditary
materials used to make an organism. A genome is made up of nucleotides that are
organized into chromosomes. These nucleotides are segments of DNA that transcribe into RNA and are translated into proteins useful to carry the genetic information of that organism.
Composition of Human Genome
The human genome is made of 3 billion nucleotide sequences and 2000 coding protein genes that make up 1% of the genome and non-coding sequences are non-protein sequences and make up the remaining 99%. More than half of the population consists of repetitive gene sequences and several copies of them are identical. The genome consists of viral DNA segments that can replicate themselves and again insert themselves into the genome. Chromosomes comprise a minor portion of the genome.
Assembly of Human Genome
The Human Genome project consists of 92 percent of DNA. The remaining 8% is the entire chromosome and includes multiple genes and repetitive DNA. Researchers used a cell path that has identical copies of each gene, which has two different copies of each chromosome. The majority of newly inserted DNA sequences were found near repeated telomeres and centromere.
Repetitive DNA sequences
Satellite is known as repetitive DNA
sequences, consisting of blocks of DNA that are repeated in tandem. But the
amount of satellite DNA in a genome varies from person to person. They are present
at the ends of chromosomes known as telomeres.
During DNA replication, these areas protect DNA from
damage. They are located in chromosome centromeres, a region that aids in
genetic information through cell division. Transcription factors that transcribe DNA into RNA within the genome, are another common type of repetitive DNA.
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| Human Genome |
History of human genome sequencing
In 2003, when the whole genome sequencing was completed there exists gaps, empty spaces and frequently repeating parts that were difficult to get sequenced. Scientists improve to join the human genome from small pieces in the early 2000s and develop new computer programs for putting together large sections of the genome. The genome published in 2013 was better than the first draft as only 8% of it was completely blank.
Scientists fill those gaps in 2021, But due to advances in technology that could manage repeating sequences, and published the first end-to-end complete human genome in 2022. After twenty years, first-time scientists have created the entire, gapless Human Genome. The telomere to telomere (T2T) team led by researchers from Human Genome sequencing Research covers the entire sequence. In 2021, the telomere-to-telomere technique, finish the complete human Genome, closing all the gaps and spaces that have been left.
How Telomere to Telomere Consortium is applied for sequencing
The T2T consortium used a complete genome sequence as a reference to discover more than two million additional variants in the human genome. According to researchers, two new techniques of DNA sequencing techniques emerged over the last decade that can read longer sequences.
With low precision, the single-cell DNA sequencing technique can read up to 1 million DNA letters also known as Nanopore technology. Still, the old sequencing techniques can read 20,000 letters with near-perfect accuracy. To obtain a full human genome sequence, researchers in T2T collaboration used both DNA sequencing methods. Short-read methods leave few gaps in genome sequencing.
Genome sequencing
The term "sequencing" refers to the
process of determining the exact order of base pairs in a DNA segment. If we
find one base pair we will find the other because they are held opposite to
each other. The Human Genome used BAC-based sequences to produce the completed form of the human genetic code. BAC is known as the Bacterial
Artificial chromosome. A "BAC library" is a mapping of BAC clones that
contain the full human genome.
The human
DNA that is split into small fragments is then cloned into bacterial clones that
store and copy human DNA, allowing it to be processed for sequencing. It takes around 20,000 distinct BAC clones to carry the 3
billion pairs of bases in the human genome.
Every BAC clone is "mapped" in the BAC-based approach to discover where the DNA in BAC copies comes from the human genome. This method assures that scientists know the precise location of each clone's sequenced DNA letters as well as their relationship to sequenced human DNA in other BAC clones.
Each BAC cloned is
split into even smaller fragments, known as Subclones of roughly 2,000 bases, for
sequencing. These subclones are subjected to a sequencer machine for sequencing. The sequencing products are subsequently put into the sequencing equipment
(sequencer). Each sequencing reaction creates around 500 base pairs of
A, T, C, and G, resulting in each base of DNA being sequenced many times. The
small sequences are then assembled into contiguous regions of sequence that
represent the human genes in the BAC clone by a computer.
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The full genome revealed 100 additional genes that
are likely to be functioning, as well as novel variations that could be linked
to disorders. Scientists have filled in missing spaces to provide a new DNA version. The researchers discovered over a hundred new genes that could be functional, as
well as millions of genetic variances between people.
When human Genome sequencing began in 1990, the sequencing
technology at that time could only read 500 nucleotides at a single time, the
entire sequence had to be recreated by overlapping tiny segments. These
overlapping regions were used to identify the next nucleotide in the Human
Genome.
This was achieved by advances in sequencing technology,
which now allows the reading of thousand-nucleotide-long sequences. The
sequencing technique is known as Next-generation Sequencing (NGS). It got easier
to locate repetitive sequences in the genome. For the first time, it was due to the availability of long-run DNA sequencing techniques that enormous repeating
sequences could be assembled using long-read sequences.
Future Sequencing Method
The new future DNA sequencing method produces life-saving drugs. Chem-map allows in vitro mapping of the small-molecule genome by transposases segmentation method. Chem-map recognizes the target DNA sequence so that the drug can interact with the genome.
The method identifies the location where molecules attach to a four-stranded structure. These quadruplexes are associated with gene regulation and would significantly serve as targets for cancer therapies in the upcoming 2023 era. With the help of our new approach, we will be able to produce medications that will be able to treat disorders like cancer in the future.
The most common anticancer medication doxorubicin binding sites in human leukemia cells were identified by this method. This technique will help us understand how various drugs affect the human genome and also produce safe and secure medication therapies.
Conclusion:
Furthermore, single-cell sequencing, long-read sequencing, and data analysis tools will deepen our understanding of the complexities of the human genome. Together with innovative tools like chem-map, these advancements will pave the way for personalized treatments, improved disease management, and transformative discoveries in genomics.
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