What are dominant and recessive factors in genetics, as identified by Gregor Mendel?What are genetic disorders?

Gregor Mendel discovered that the genotype is an organism's genetic makeup. For example, all of your genes are what comprise your genotype. The expression of those genes is called your phenotype, your traits that result when the instructions in your genes are carried out.  "Alleles are variations of a gene. We get one set of alleles (genes) from one parent and the other set of alleles from the other parent.

Some of the traits that we have are based on simple inheritance where one version of a gene (dominant allele) masks, or hides the expression of the other version of that gene (recessive allele).

In writing, we represented dominant and recessive alleles with letters that distinguish the different types of alleles. A capital letter is used to represent the dominant allele and a lower-case letter is used to represent the recessive allele (example: dominant gene = P; recessive gene = p)." For a recessive trait to appear the offspring must receive two recessive genes from the parents.

Genetic disorders are caused by a mutation of a gene on a strand of DNA.  This can come from a parent who is a carrier of the recessive gene and doesn't know it, or it can come from a mutation during development of the embryo.