06 Molecular Evolution

orthologous genes

Homologous genes passed in a straight line from one generation to the next. The same gene in different species

Paralogous genes

genes that are copies of each other, in same species

Replication errors (point mutations)

Single nucleotide changes• Indels (insertion-deletion) smaller than a gene

Mitotic and Meiotic errors

Unreduced gametes (i.e., 2n gametes instead of normal 1n)

• Result in whole genome duplication. Chromosome segregation errors result in aneuploidy. Aberrant crossovers result in duplication and loss of genes

•Depending on size, parts of genes could be parts of large regions with multiple genes

Retrotransposition

is the process where a gene or DNA sequence is copied from RNA back into DNA and inserted into a new location in the genome. Can cause mutations or errors

what is a major source of evolutionary novelty?

mitotic and meiotic errors

Transposable elements

selfish genetic elements replicate themselves within a genome (virus-like parasites)

What error is most common in plants?

Mitotic and meiotic errors

what leads to aneuploidy and is deleterious?

mitotic and meiotic errors since some chromosome segregation errors result in an abnormality in the # of chromosomes in a cell. Some have a lack of Y chromosome XO turner syndrome. Some have Down syndrome or an extra X chromosome

pseudogenization (gene inactivation)

These are processes by which a DNA sequence that resembles a gene becomes mutated and inactive. Pseudogenes are nonfunctional segments of DNA and could happen to new or original copies. the most common fate of new duplicates. Ex: Olfactory genes, 70 percent of them are inactive in humans

Sub-functionalization

a process where duplicated genes take on different parts of the original gene's functions. Each gene evolves to specialize in one of the functions of the original gene (doesn't just create new functions though)

Neofunctionalization

An evolutionary process in which duplicated genes diverge, and one copy takes on a new function it didn't have before while the other one is the copy.

DNA Junk elements

Pseudogene = inactive copies. Introns = junk DNA Transposable elements+ pieces of DNA that replicate and insert themselves in new places (selfish DNA)

Composition of the Human genome

3.2 billion base pairs but only 2% codes for functional proteins, we have a lot of junk DNA/ extra

horizontal gene transfer

Genes passed from one organism to another, unrelated organism, common in prokaryotes. Not mutation but acquisition of new genetic variation

How did Random Genetic Drift leave footprints?

Genome-wide reduction in polymorphism- i.e. effects the whole genome- "global effect"

How does natural or sexual selection leave footprints?

Reduced nucleotide variation, but only for the gene under selection- i.e. effects specific genes- "regional effect"

How does migration leave footprints?

-Measure patterns of neutral variation among populations

- Large differences in allele frequencies among populations mean low migration rates (low gene flow)

-usually genome-wide effect (unless combined with selection)