Genomes and Evolution

Genome data helps scientists trace how organisms are related over time. When two species share a common feature, it is often encoded by DNA sequences that have stayed conserved in both species. As genome sequencing improved in the late 20th century, researchers gained a better way to compare conserved domains across species and use that evidence to infer evolutionary relationships.

Genome comparison can show evolutionary relationships at three levels. At the broadest level, it highlights...

DNA replication includes built-in error checks that protect the genome during cell division. Even though this process copies millions of base pairs with high fidelity, a wrong base or a longer stretch of wrong bases can still be added to the daughter strands. If these mistakes are not corrected, cells may build up mutations that can threaten survival.

One level of repair is proofreading. DNA polymerase enzymes, which build the new DNA strand, can make about 1 incorrect nucleotide per 100,000...

Phylogenetic trees show how organisms are related through evolution. They map branching patterns that trace common ancestry and help scientists compare species over time.

A phylogenetic tree can be read like a family tree for life. Each branch point marks a split from a shared ancestor, and the pattern of branches shows how closely related different organisms are.

These trees are used to organize biological information and to study evolutionary change. They can also help scientists understand...

Chromosome rearrangements and synteny show how shared gene order can reveal evolutionary history. Synteny means genes are found on the same chromosome, even if they are not genetically linked. John H. Renwick coined the term in 1971. Species with common ancestry often keep conserved syntenic regions.

Scientists use synteny to compare the evolutionary relationship between species. Human and mouse lineages split from a common ancestor about 80 million years ago. Since then, the ancestral...

Conserved DNA across species shows how some genome regions stay nearly unchanged over time. Next-generation sequencing has built large genome databases for many animals and plants. Since the Human Genome Project, scientists have compared the genomes of primates, mammals, and other distant species. These large studies have helped reveal evolutionary relationships between organisms.

Although species genomes differ greatly, a few DNA sequences are highly conserved. Conserved DNA sequences found...

Gene duplication helps drive evolution by creating extra copies of DNA that can change over time. The seminal work of Ohno in 1970 helped popularize this idea. DNA sequence comparisons show that many genes in bacteria, archaebacteria, and eukaryotes came from duplication and later divergence, which makes this process important in evolution.

The duplicated copies of a gene are called paralogs. When paralogs have similar sequences and functions, they form a gene family. Many gene families have...

Exon recombination helps new genes form by mixing exons from the same gene or from different genes. This process is also called exon shuffling or domain shuffling. It has been seen in vertebrates, invertebrates, and some plants, including potatoes and sunflowers.

During exon recombination, exons join in new exon-intron combinations. These new combinations may later become new genes. Exon shuffling follows splice frame rules, which means the exons must fit the reading frame correctly.

Each...

Genome variation in CNVs and SNPs shows how DNA can differ across people in a population. These differences may involve a single nucleotide, which is one DNA base, or a larger chromosomal change. Scientists study them to understand inherited variation in the human genome.

Copy number variations, or CNVs, are structural changes that cover more than 1 kb of DNA sequence. A CNV can change the number of copies of a gene or a group of genes. The main forms are deletion, tandem duplication,...