Human genome project
- The scientific project which deal with the study of base sequences of DNA molecules of complete set of chromosomes is called human genome project.
- HGP was closely associated with the rapid development of a new area in biology called as
- Goals of Human Genome Project
- Identify all the approximately 20,000-25,000 genes in human DNA.
- Determine the sequences of the 3 billion chemical base pairs that make up human DNA.
- Store this information in databases;
- Improve tools for data analysis;
- Transfer related technologies to other sectors, such as industries;
- Address the ethical, legal, and social issues (ELSI) that may arise from the project.
Methodologies
- To identifying all the genes that expressed as RNA referred to as Expressed Sequence Tags (ESTs).
- Simply sequencing the whole set of genome that contained all the coding and non-coding sequence, and later assigning different regions in the sequence with functions is called as Sequence Annotation.
- The total DNA from a cell is isolated and converted into random fragments of relatively smaller sizes and cloned in suitable host using specialised vectors.
- The cloning resulted into amplification of each piece of DNA fragment.
- The commonly used vectors are BAC (bacterial artificial chromosomes), and YAC (yeast artificial chromosomes).
- The fragments were sequenced using automated DNA sequencers.
- Specialized computer based programmes were developed for the alignment of the sequences.
- The sequences were subsequently annotated and were assigned to each chromosome.
- The sequence of chromosome 1 was completed only in May 2006.
Automated DNA sequencer
Salient Features of Human Genome
- The human genome contains 3164.7 million nucleotide bases.
- The average gene consists of 3000 bases with the largest known human gene being dystrophin at 2.4 million bases.
The largest known human gene- dystrophin
- The total number of genes is estimated at 30,000.
- 9 per cent nucleotide bases are exactly the same in all people.
- The functions are unknown for over 50 per cent of discovered genes.
- Less than 2 per cent of the genome codes for proteins.
- Repeated sequences make up very large portion of the human genome.
- Repetitive sequences are stretches of DNA sequences that are repeated many times.
- Chromosome 1 has most genes (2968), and the Y has the fewest (231).
- Scientists have identified about 1.4 million locations where single base DNA differences (SNPs – single nucleotide polymorphism) occur in humans.
Single nucleotide polymorphism (self-drawn )
Applications of HGP
- All the genes in a genome can be studied together.
- Helps to understand how tens of thousands of genes and proteins work together in interconnected networks.
- Helps to diagnose and treat genetic diseases.
