What determines how often a phenotype occurs in a population?

Question

Please tell me!
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Answer 1

Phenotype is determined by what genes you carry. There are many variations on a gene called alleles. Depending on what alleles you inherit from your parents (use a Punnet Square for that) you get a different phenotype. In a population, mating patterns can also be a big thing. Often times, animals will refuse to mate with creatures that have different appearances or phenotypes than them. Because of this, that particular phenotype is rarely seen.

Answer 2

Population genetics will determine the relative frequency of mendelian traits via Hardy-Weinberg equilibrium. However, for polygenic traits and even monogenic ones there are multiple factors that affect whether or not a phenotype occurs within a population. The first thing to consider is whether there exists locus and allelic heterogeneity for the phenotype, meaning multiple genes/genotypes can independly and also by their interaction determine whether or not a phenotype is present. Also for a single gene multiple alleles exist that can affect the phenotype. This in part can determine the penetrance of a phenotype, which means how often it occurs even when there is the correct genotype for it. Rarely do we see phenotypes that are 100% penetrant, thus geneticists talk of imcomplete penetrance. An important fact to remember is that even dominant traits can skip a generation for various reasons and is often observed in clinical genetics. Another factor to consider is variable expressivity, this is in regards to the variability of any one phenotype as far as range/degree affected. An example is having four and a half fingers rather than five and the phenotype is missing fingers. We are technically missing a part of a complete finger, and the missing fingers phenotype is penetrant in this sense. Much more can affect how often a phenotype occurs like the prevalence of modifier genes and the gene itself that causes the phenotype in the population. Cheers.

Answer 3

The variation of the genotype. The allele frequency. The proportion of dominate to recessive traits.

Answer 4

The Hardy-Weinberg equation.

Answer 5

the hardy-weinberg equation p^2+2pq+q^2=1