Download Mendelian Inheritance

Modern Genetics
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Recessive albinism. The allele encodes an enzyme which is required
for pigment synthesis or deposition. (Humans; mice; penguins.)
Dominant color suppression. The allele encodes a regulatory
protein which represses synthesis or deposition of pigment. (Horse;
foxglove)
Traits result from complex interactions:
 (1) among the products of genes;
 (2) between genes and regulatory proteins expressed by other
genes;
 (3) between genes and proteins, and environmental factors such as
nutrients, temperature, etc.;
 (4) chance effects during development.
The reason Mendelian inheritance can be seen to "work" is that in many
cases we can hold all the above factors constant, for a given genotype
(genes affecting a trait) and a given phenotype (appearance of trait).