Heterozygous & Homozygous.

Mangile's Pigeon Pages

Heterozygous & Homozygous

The unfamiliar words, e.g., heterozygous, homozygous and hemizygous, are inescapable when trying to establish precisely what is being discussed. Following are some definitions that may help with the derivation of these words.

A zygote is: the cell formed by the union of two gametes (sperm and ovum).

The suffix -zygous implies: a zygotic constitution of a specified kind.

The prefix hetero- means: different (or, not alike).

The prefix homo- means: same (or, alike).

The prefix hemi- means: half (or, partial).

The term heterozygous means: having dissimilar genes at corresponding loci.

The term homozygous means: having identical genes at corresponding loci.

The term hemizygous means: having no allelic counterpart; unpaired gene at a locus; - (typical of the sex-linked genes in female pigeons).

Note: The versatility of a pencil is lost when using a typewriter. For example: the numeric fraction one-fourth is express as 1/4 when typewritten on the same line. For expressing typewritten genotypes the adoption of the forward slash "/" is used to represent an unpaired chromosome, and a double-slash "//" to represent paired chromosomes. Gene symbols are typewritten adjacent to their respective chromosome. The genotype of a brown cock that is heterozygous for reduced is written - "rb//+b". Please note - the "+" symbol in the genotype is used to express a wildtype gene opposing the reduced "r" gene - at the reduced locus.

Following are some genotypes for sex-linked genes only:

Genotype: Sex: Phenotype: Description:

B^A//+ cock ash-red heterozygous for ash-red

b//+ cock wildtype heterozygous for brown

+//r cock wildtype heterozygous for reduced

B^A//B^A cock ash-red homozygous for ash-red

b//b cock brown homozygous for brown

r//r cock reduced homozygous for reduced

d//d cock dilute homozygous for dilute

d+//db cock dilute homozygous for dilute & heterozygous for brown

rb//+b cock brown heterozygous for reduced & homozygous for brown

db//db cock dilute-brown homozygous for dilution & brown

B^A/. hen ash-red hemizygous for ash-red

b/. hen brown hemizygous for brown

dB^A /. hen dilute-ash-red hemizygous for dilute & ash-red

db/. hen dilute-brown hemizygous for dilution & brown

* * Index * *

Genotype:	Sex:	Phenotype:	Description:
B^A//+	cock	ash-red	heterozygous for ash-red
b//+	cock	wildtype	heterozygous for brown
+//r	cock	wildtype	heterozygous for reduced
B^A//B^A	cock	ash-red	homozygous for ash-red
b//b	cock	brown	homozygous for brown
r//r	cock	reduced	homozygous for reduced
d//d	cock	dilute	homozygous for dilute
d+//db	cock	dilute	homozygous for dilute & heterozygous for brown
rb//+b	cock	brown	heterozygous for reduced & homozygous for brown
db//db	cock	dilute-brown	homozygous for dilution & brown
B^A/.	hen	ash-red	hemizygous for ash-red
b/.	hen	brown	hemizygous for brown
dB^A /.	hen	dilute-ash-red	hemizygous for dilute & ash-red
db/.	hen	dilute-brown	hemizygous for dilution & brown