1. Although human genome contains 3 billion nucleotide bases, the DNA sequences that encode proteins make up only about 5% of the genome.
2. An average gene consists of 3000 bases, the largest known human gene being dystrophin with 2.4 million bases.
3. The function of 50% of the genome is derived from transposable elements such as LINE and ALU sequence.
4. Genes are distributed over 24 chromosomes. Chromosome 19 has the highest gene density. Chromosome 13 and Y chromosome have lowest gene densities.
5. The chromosomal organization of human genes shows diversity.
6. There may be 35000-40000 genes in the genome and almost 99.9 nucleotide bases are exactly the same in all people.
7. Functions for over 50 percent of the discovered genes are unknown.
8. Less than 2 percent of the genome codes for proteins.
9. Repeated sequences make up very large portion of the human genome. Repetitive sequences have no direct coding functions but they shed light on chromosome structure, dynamics and evolution (genetic diversity).
10. Chromosome 1 has 2968 genes, whereas chromosome ’Y’ has 231 genes.
11. Scientists have identified about 1.4 million locations, where single base DNA differences (SNPs – Single nucleotidepolymorphism – pronounce as ‘snips’) occur in humans. Identification of ‘SNIPS’ is helpful in finding chromosomal locations for disease associated sequences and tracing human history.
