Genomes
Genomes
- The term genome can be defined as follows:
All of the genetic information in an organism
- This refers to the DNA present within every cell of an organism
- This includes genes that code for proteins as well as non-coding DNA sequences
- Mitochondrial DNA and chloroplast DNA are included in the genome of eukaryotic cells
- In a prokaryote cell, plasmid DNA is included in the genome
Unity and diversity of genomes
- Advances in technology have allowed scientists to determine the entire base sequence of the genes within an organism's genome
- Determining the base sequence of DNA is referred to as DNA sequencing
- Genome-wide comparisons can now be made between individuals and between species
- Comparisons show that there is a high level of genome similarity within, and even between, species
- Humans share around 99.9 % of their DNA with other humans
- Humans share around 99 % of their DNA with chimpanzees
- Humans in fact share all of their coding genes with other humans; the differences between individual humans are due to possessing different alleles of genes
- Different alleles arise due to mutations
- Differences between DNA sequences that involve a single base change are known as single nucleotide polymorphisms (SNPs)
- Because SNPs are areas of difference between individuals who share 99.9 % of their DNA, scientists will often use SNPs to determine ancestry or disease risk
Single nucleotide polymorphism diagram
A difference in a single nucleotide is known as a single nucleotide polymorphism, or SNP. Most SNPs have no effect on the protein produced, but a few may lead to production of an altered protein.