Natural Selection Flashcards
Selection acts on genetic variation to
produce new phenotypes
coat phenotypes
Combinations of alleles at three genes create seven different COAT PHENOTYPES
They identified distinct mutations in three genes, RSPO2, FGF5, and KRT71 that together account for most coat phenotypes in purebred dogs in the United States.
due to selective inbreeding
dogs have a bevy of breed-specific behaviors, and their genomes make it possible to track down the genes responsible.
Williams-Beuren syndrome
syndrome leads to mental disability and an “elfin” appearance, but also often makes a person very trusting and friendly.
results from the loss of part of chromosome 7.
GIF21
Disruption on a gene for a protein called GIF21, which regulates the activity of other genes, was associated with the most social dogs.
relative lack of changes in that gene seems to lead to aloof, wolflike behavior,
adaptations
Populations change when individuals within the population acquire characteristics that improve their reproductive success,
green anole lizard
During the winter of 2013–2014, the SE United States endured an extreme cold event.
Gene expression in southern survivors shifted toward patterns characteristic of northern populations.
Extreme winter events can rapidly produce strong selection on natural populations.
Factors that Govern Microevolution Sources of New Genetic Variation
new alleles
gene duplication
exon shuffling
horizontal gene transfer
new alleles
Random mutations within pre-existing genes introduce new alleles into populations, but at a very low rate
gene duplication
Abnormal crossover events and transposable elements may increase the number of copies of a gene.
Over time, the additional copies can accumulate random mutations and create a gene family.
exon shuffling
Abnormal crossover events and transposable elements may promote gene rearrangements in which one or more exons from one gene are inserted into another gene.
horizontal gene transfer
Genes from one species may be introduced into another species.
Events such as endocytosis and interspecies mating may promote this phenomenon.
lactase persistence
trait for Lactase Persistence emerged about 4,300 - 7,500 years ago in Hungry
cytosine changed to thymine in a genomic region not far from the lactase gene
might have allowed people to stay alive during times of drought. People would have been able to drink milk without getting sick.
People whose ancestors had herded cattle had evolved to make use of milk
Dinka people of southern Sudan, the Maasai, who live in Kenya and northern Tanzania, and the Zulu, Xhosa and Swazi of South Africa all rely on herding for survival. These people drink milk.
gene for lactase, the enzyme that breaks lactose down into the more digestible forms of glucose and galactose, is normally switched off as children are weaned.
were three mutations that were associated with lactase persistence in Africa and these were independent of the genetic mutation that seemed to cause lactase persistence in North Europeans.
evolution of lactase persistence is one of the best cases of CONVERGENT EVOLUTION in humans.
Another case of convergent evolution
evolution involves skin color. Lighter skin color seems to have evolved independently in Europe and Asia.
