Inheritance: information that is passed on from one generation to the next. (Watson, xi) The transmission of traits between generations. (Lewis, 2) Autosomal dominant, autosomal recessive, X-linked, multifactorial, and mitochondrial inheritance are examples. (GeneReviews)

Today we understand that a fertilized egg contains the genetic information contributed by both parents. That is heredity. The subsequent process, the development of a new individual from that humble starting point of a single cell, involves implementing that information. (Watson, 6) Adjective - ‘hereditary.' Also referred to as 'inheritance factors,' 'inheritance patterns,' 'patterns of inheritance,' 'modes of inheritance,' and 'heredity.'

Congenital: any "trait" present at birth, whether the result of a "genetic" or nongenetic factor. (HGPIA) Used with "disease" headings to indicate those conditions existing at, and usually before, birth. It excludes "morphologic" abnormalities and birth injuries. (MeSH) Birth defects are described as being "congenital." They can be caused by a "gene mutation,” an unfavorable "environment" in the “uterus,” or a combination of both factors. (NHGRI)

Dizygotic Twins (DZ Twins): two “offspring” from the same “pregnancy.” They are from two “ova,” fertilized at about the same time by two “spermatozoa.” Such twins are genetically distinct. (MeSH) They share half of their genes, just like any other siblings. Can be of the same or different sexes. (NHGRI) The tendency to have DZ twins may run in families if the women sometimes ovulate two “oocytes” in a month. (Lewis, 57) Also referred to as ‘fraternal twins.’

Endogenous: produced inside an "organism" or "cell." The opposite is external (exogenous) production. (NCIt) Carried from "generation" to generation. (Lewis, 207)

Haplotype: a collection of variable "DNA sequences" that tend to be inherited together. (GNN) A way of denoting the collective "genotype" of a number of closely linked "loci" on a "chromosome." (HGPIA) A set of DNA "variations," or "polymorphisms," that tend to be inherited together. A haplotype can refer to a combination of "alleles" or to a set of "SNPs" found on the same chromosome. (NHGRI)

Hybrid: offspring of parents. (Norman, 7/21/09) Offspring of two individuals with different characteristics or traits ("phenotypes"). (Brooker, G-18) For example, an experiment could involve a cross between a purple-flowered plant and a white-flowered plant. (Brooker, 326)

Monozygotic Twins (MZ Twins): two offspring from the same pregnancy. They are from a single fertilized “ovum” that split into two “embryos.” Such twins are usually genetically identical and of the same sex. (MeSH) Share all of their genes and are always of the same sex. (NHGRI) They are natural “clones.” MZ twins occur in 3 to 4 pregnancies per 1,000 births worldwide. In North America, twins occur in about 1 in 81 pregnancies, which means that 1 in 40 of us is a twin. (Lewis, 57-58) Also referred to as ‘identical twins.’

Offspring: a human descendant (son or daughter) of any age. (NCIt)