lec 14- evolution and phenotypes Flashcards
is selection by itself evolution?
no, it can lead to evolution if selection alters genetic fitness in the population
will the sticklebacks potentially see a shift in their phenotype of low armour?
yes because the water are now more clear due to less algae meaning more predation and the need for more armour
what is epigenetics?
modifications of DNA that does not involve changes in nucleotide sequences
what is a key factor to why some identical twins develop diseases that the other doesn’t have even though there DNA are identical?
Methylation (adding CH3) to DNA nucleotides which can cause parental alleles to be represented over the other
what does methylation do?
it adds a methyl group to DNA or RNA which can inactivate or silence a gene
how much of our genome is old viral DNA or RNA that can be activated but undergo methylation to prevent certain transposed DNA elements from spreading further?
45%
what are the two types of selection that maintain diversity in populations (keep alleles in the gene pool)?
- negative frequency dependent selection
- heterozygote advantage
what is negative frequency-dependent selection?
when a genotype has a higher fitness when it is rare
how does negative frequency dependent selection work when compared to yellow and purple orchids?
-bees visit purple orchids and realize no nectar is there, so no reward
-this causes bees to go to rarer color like yellow, allowing the yellow population to grow in fitness
what is heterozygote advantage?
when individuals with two different alleles have a higher chance of survival then those with identical alleles
what is the heterozygote advantage seen in sickle cell anemia?
SS homozygotes have sickle cell anemia which is lethal but those who are heterozygotes (AS) have normal and sickle cell trait of hemoglobin, which allows it to not be fatal
are both AS alleles maintained by selection in areas with high sickle cell anemia rates to maintain genetic diversity?
yes
what are the three types of landscapes that affect genetic structure and evolution of populations?
- no subdivision: continuous population structure, high levels of interbreeding, gene flow continuous
- extreme subdivision: highly isolated populations, little gene flow between smaller populations
- intermediate subdivision: some isolation and breeding barriers, but some gene flow happens
how do large ranges vs small scattered populations effect evolution?
-large population have more gene flow but lower chances of speciation
-small isolated populations have low gene flow but higher chance for speciation
what are some barriers that limit gene flow?
-urbanization which causes isolated patches of wildlife
-oceans and rivers
-mountains and valleys
do barriers cause genetically distinct populations of one species?
yes
what causes spirit bears to occur?
-a point mutation, frequency of this recessive mutation is high on few island populations on the north coast of BC
-white fur is due to a Tyr-to-Cys replacement in the MC1R gene
do spirit bears have an advantage to hunting?
yes, harder for salmon to see them due to them being similar in color to water
when is genetic distance increased?
among more isolated populations of a species
what are additive alleles?
alleles that contribute to a phenotype in a quantitative way, the more of the alleles results in more effect of phenotype
are additive alleles important for quantitative genetics?
yes
what is important to quantitative genetics?
additive alleles because the effect can be calculated by summing the number of additive alleles present
are additive alleles always exposed to selection?
yes, can either be fixed or eliminated
what creates continuous distributions for additive genes?
genetic and environmental influences together
can rapid environmental change lead to a mismatch between plastic genetic traits and altered eniornments?
yes, changes in the environment can cause changes in the plasticity of a trait with its timing like hairs being white in spring rather than winter
