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.

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:
BA//+  cock ash-red  heterozygous for ash-red
b//+ cock wildtype  heterozygous for brown
+//r cock wildtype  heterozygous for reduced
BA//BA 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
BA/. hen ash-red hemizygous for ash-red
b/.  hen brown hemizygous for brown
dBA /. hen dilute-ash-red hemizygous for dilute & ash-red
db/. hen dilute-brown hemizygous for dilution &  brown
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