zygo-, zyg-, -zygous; zygomatico- +

(Greek: yoke, forming pairs; joined, union; or indicating a relationship to a junction; meaning a yoke or crossbar by which two draft animals; such as, oxen could be hitched to a plow or wagon)

dizygous (adjective) (not comparable)
Pertaining to two separate zygotes or two separately fertilized eggs: Dizygous twins can be of the same gender or of opposite gender, and have evolved and grown from two individually fertilized ova.
duplex zygote (s) (noun), duplex zygotes (pl)
A fertilized ovum which has two identical genes for a given dominant character.
hemiazygos vein (s) (noun), hemiazygos veins (pl)
An intercepting trunk for the lower left posterior intercostal veins: The hemiazygos vein arises from the ascending lumbar vein, passes up on the left side of the vertebrae to the eighth thoracic vertebra, where it may receive the accessory branch, and crosses over the vertebral column to open into the azygos vein.
hemizygous (adjective) (not comparable)
Referring to a single copy of a gene instead of the customary two copies: All of the genes on the single X chromosome in the male are in the hemizygous state.
heterozygosis (s) (noun), heterozygoses (pl)
The formation of a zygote by the union of gametes of unlike genetic constitution: Jill learned in her biology book that heterozygosis is the fusion of two genetically unlike gametes.
heterozygosity (s) (noun), heterozygosities (pl)
The state of possessing different alleles (alternative forms of a gene that can occupy a particular chromosomal locus) at a given locus in regard to a given character: Mr. Smith tried to avoid breeding animals that showed heterozygosity for possible illnesses causing alleles.
heterozygote (s) (noun), heterozygotes (pl)
An individual possessing different alleles, or forms of genes, in regard to a given character: It was evident that Thomas was a heterozygote because he was endowed with a copy of each allele.
heterozygous (adjective) (not comparable)
Concerning genetic variants or dissimilar pairs of genes for any hereditary characteristic: A heterozygous cell or organism has two or more different versions of alleles, or forms of the same gene, of at least one of its genes.

The offspring of such an organism may differ with regards to the characteristics determined by the gene or genes involved, depending on which version of the gene they inherit.

homozygosis (s) (noun), homozygoses (pl)
The formation of a zygote by the union of gametes that possess one or more identical alleles.

An "allele" is one member of a pair or series of genes that occupy a specific position on a specific chromosome.

homozygosity (s) (noun), homozygosities (pl)
The state of possessing a pair of identical alleles at a given locus: In the different study groups no homozygosity was discovered.

Homozygosity has two identical genes at the corresponding loci of homologous chromosomes.

homozygote (s) (noun), homozygotes (pl)
An individual possessing a pair of identical alleles at a given locus or a cell or organism that has two of the same forms of a particular gene: Jill was a homozygote because she had two blue eyes!
homozygous (adjective), more homozygous, most homozygous
Regarding an organism that has exactly the same alleles for any one gene: The two brothers are homozygous because they both have brown eyes!
merozygote (s) (noun), merozygotes (pl)
A bacterial mechanism of gene transfer in which part of the genome, or chromosome complement, is transferred into an intact recipient cell.
monozygosity (s) (noun) (no pl)
The condition of having been derived from one fertilized ovum: After reading about twins and triplets in her biology book, Jane now knew what was meant by monozygosity and that it was a term used to describe her twin friends, Janice and Alice, who were identical in all respects!
monozygotic, monozygous (adjective) (not comparable)
Pertaining to one zygote or a single ovum, a female reproductive cell or egg: Jack and Tom are monozygotic twins and have the same genetic code, while Susan and Sandy are genetically "dizygotic" twins and are considered to be ordinary siblings.