Read the given passage and answer the following questions:
In the preceding sections you have learnt that it is the sequence of bases in DNA that determines the genetic information of a given organism. In other words, genetic make-up of an organism or an individual lies in the DNA sequences. If two individuals differ, then their DNA sequences should also be different, at least at some places. These assumptions led to the quest of finding out the complete DNA sequence of human genome. With the establishment of genetic engineering techniques where it was possible to isolate and clone any piece of DNA and availability of simple and fast techniques for determining DNA sequences, a very ambitious project of sequencing human genome was launched in the year 1990. Some of the important goals of HGP were as follows: (i) Identify all the approximately 20,000-25,000 genes in human DNA; (ii) Determine the sequences of the 3 billion chemical base pairs that make up human DNA; (iiii) Store this information in databases; (iv) Improve tools for data analysis; (v) Transfer related technologies to other sectors, such as industries; (vi) Address the ethical, legal, and social issues (ELSI) that may arise from the project. The Human Genome Project was a 13-year project coordinated by the U.S. Department of Energy and the National Institute of Health. During the early years of the HGP, the Wellcome Trust (U.K.) became a major partner; additional contributions came from Japan, France, Germany, China and others. The project was completed in 2003.
The locations in the human genome where single-base DNA differences occur are called:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → SNPs
Almost all the nucleotide bases are the same in all humans. At some sites, however, people differ by one base. These sites are called single nucleotide polymorphisms (SNPs), pronounced “snips”. They help in finding the chromosomal locations of disease-associated sequences and in tracing human history. ESTs (Expressed Sequence Tags) are genes expressed as RNA, while VNTRs (Variable Number of Tandem Repeats) and microsatellites are short repeated sequences used in DNA fingerprinting; none of them is a single-base difference.
NCERT Extract:
Salient Features of Human Genome – “… Almost all (99.9 per cent) nucleotide bases are exactly the same in all humans. … (ix) Scientists have identified about 1.4 million locations where singlebase DNA differences (SNPs – single nucleotide polymorphism, pronounced as ‘snips’) occur in humans. This information promises to revolutionise the processes of finding chromosomal locations for disease-associated sequences and tracing human history.”