10- Human Genome project (2).pdf

The Human Genome Project Prepared by Dr. Somaya Elbushra MBBS MSc MPHE 1  Genomics is the study of the complete DNA (genome) sequence of an organism. In the mid 1980s, a number of scientists think of sequencing the human genome....

The Human Genome Project Prepared by Dr. Somaya Elbushra MBBS MSc MPHE 1  Genomics is the study of the complete DNA (genome) sequence of an organism. In the mid 1980s, a number of scientists think of sequencing the human genome. The project started in 1990. Two technologies enabled the project: gene mapping and DNA sequencing. As a part of the Human Genome Project (HGP), the genomes of several organisms (E. coli, C. elegans, and D. melanogaster) were also sequenced. 2 Assembling and Finishing Genome Sequences: The DNA sequences obtained are assembled into larger sequences by computer based on the sequence overlaps. Gaps remaining at this point are filled in by subsequent sequencing in a process known as finishing. HGP (1990-2003) produced a high-quality human genome sequence, accounted for 92% of the human genome. 19 years later (in 2022), a truly complete (‘telomere-to-telomere’) human genome sequence was finally generated 3 Draft Sequence of the Human Genome: The estimated number of genes is about (20,000-25,000). The average gene consists of about 40,000 bases. The largest known human gene is dystrophin about ( 2.4 million bases). The DNA sequence in any two individuals is (99.9 %) identical. 4  The functions are unknown for over 50% of the discovered genes. Less than (2 %)percent of the genome codes for proteins. Repeated sequences that do not code for proteins make up at least (50%) of the human genome. Chromosomes, which range in size from 50 million to 250 million bases. Somaya Elbushra 5  The gene-rich regions of the genome are predominantly composed of the bases guanine and cytosine. gene-poor regions, the bases adenine and thymine dominate. Genes appear to be concentrated in random areas along the genome, with vast expanses of noncoding DNA in between. Chromosome 1 has the most genes (about 3,000) and the Y chromosome has the fewest (about 230). 6 Human Compares with Other Organisms: Humans share most of the same protein families with worms, flies, and plants, Humans have on average three times as many kinds of proteins as the fly or worm 7 Variations and Mutations: Over 3 million single nucleotide polymorphisms (SNPs) have been found in the human genome. SNPs are common single-base variations in the genome. They are being used to identify regions of the genome associated with disease. The ratio of germline (sperm or egg cell) mutations is 2:1 in males vs females 8 Dr Somaya Eblushra 9