mendels genetics, lectures 18-21 Flashcards
what is stabilising selection
Stabilising selection, reduces variation in the population but does not change the mean phenotype.
what is directional selection
Directional selection changes the mean towards a more extreme value.
what is disruptive selection
Disruptive selection favours two different extremes, so it creates two peaks.
what is frequency dependant selection
Frequency dependant selection: where selection maintains an even amount of two phenotypes, but one is more actively selected against when it is higher proportion.
what is a cline
A cline is a gradual change in genotype or phenotype over a geographic area.
what are the two Hardy-Weinberg equations
P^2 + 2PQ + Q^2 =1
P+Q =1
what are mendels two laws
law of segregation and law of independant assortment
what does the law of segregation mean
“Genes segregate at meiosis so that
each gamete contains only one of the
two possessed by the parent
what does the law of independant assortment mean
Alleles of different genes assort
independently during gamete formation
what is polymorphic
when one gene has many alleles
what is incomplete dominance
: where neither is completely dominant so an intermediate Is expressed, so the snap dragons, red and white flower can make pink
what is codominance
both are equally dominant, so they are both present equally in the phenotype. The phenotype will be an additive effect of the two genes together. So like the pattern on the clover example.
what are polygenic traits
when the phenotype is controlled by many genes that have an additive effect, like all the genes contributing to skin colour
the alleles for a specific trait are found at a what-on who
found at a specific locus on a particular chromosome
