Chapter 21

• Genomics is the study of whole sets of genes and their interactions within a species, and genome comparisons between species
• Bioinformatics is the application of computational methods to the storage and analysis of biological data
• The Human Genome Project fostered development of faster, less expensive sequencing techniques
• The most ambitious mapping project to date has been the sequencing of the human genome
• Genomes vary in size, number of genes, and gene density
• Genomes of most bacteria and archaea range from 1 to 6 million base pairs (Mb); genomes of eukaryotes are usually larger
• Most plants and animals have genomes greater than 100 Mb; humans have 3,000 Mb
• Free-living bacteria and archaea have 1,500 to 7,500 genes
• Unicellular fungi have about 5,000 genes and multicellular eukaryotes up to at least 40,000 genes
• Number of genes is not correlated to genome size
• Sequencing of the human genome revealed that 98.5% does not code for proteins, rRNAs, or tRNAs
• Gene regulatory sequences and introns account for 5% and 20%, respectively, of the human genome
• Noncoding DNA found between genes includes Pseudogenes, former genes that have accumulated mutations and are nonfunctional, and Repetitive DNA, present in multiple copies in the genome
• The basis of change at the genomic level is mutation
• Accidents in meiosis can lead to one or more extra sets of chromosomes (polyploidy)
• Humans have 23 pairs of chromosomes, while chimpanzees have 24 pairs
• One copy of a duplicated gene can undergo alterations that lead to a completely new function for the protein product
• Multiple copies of similar transposable elements facilitate recombination, or crossing over, between different chromosomes
• Comparative studies of genomes help understand evolutionary history of life and explain morphological diversity
• Highly conserved genes have changed very little over time, helping clarify relationships among species that diverged from each other long ago
• Human and chimpanzee genomes differ by 1.2% at single base-pairs and by 2.7% because of insertions and deletions
• Humans and chimpanzees differ in the expression of the FOXP2 gene, whose product turns on genes involved in vocalization