Reprinted with permission from:
Dr. Joanne Norton
Published with permission from BowTie Inc. http://www.FishChannel.com
Freshwater And Marine Aquarium magazine
Photos and Text by Dr. Joanne
FAMA: July 1982, Vol. 5, #7
2, I discussed the inheritance of mutant genes
that affect the color of aquarium-bred angelfish. In
this article I shall add information on the location
of these genes. This additional knowledge is
essential in order to know which gene combinations
are possible and also to enable you to predict
correctly the outcome of crosses involving more than
one mutant gene.
The angelfish's chromosomes (containing the
genetic material) are in pairs, one chromosome of
each pair having come from each parent. Each gene
occurs at a specific location, called locus (plural,
loci), on the chromosome. Variations of a gene are
called alleles. Only one allele occurs at a locus;
another allele of that gene can occur at the same
locus on another chromosome.
Tests for Allelism
A marble female (having two doses of marble),
mated to a black lace male (one dose of dark),
produced 23 marble and 22 black (one dose of marble
and one dose of dark). This type of black angelfish,
called marble lace (Norton, 1971), has a marbled
pattern on the body that can be seen by shining a
flashlight on the fish. A true black (two doses of
dark) has faint vertical body stripes that can be
seen by using a flashlight.
Black Angel. (1 dose of dark and 1 dose of marble.)
When a wild-type (silver) female was mated to a
marble lace male, the offspring were 48 black lace
and 46 marble. Since there were no wild-type
offspring, I concluded that the genes for dark (D)
and marble (Dm) act as alleles. In other words,
these genes are at the same locus.
A wild-type female and zebra lace male (one dose
each of dark and zebra) produced 9 wild-type, 6
black lace, 4 zebra, 5 zebra lace. It is concluded
that the genes for dark (D) and zebra (Sze) are not
alleles since the above cross produced some
Zebra Lace. (1 dose of Zebra and 1 dose of dark.)
A new gold female and true black male (D/D)
produced 100% black, which were not as deeply
pigmented as the true black. This type of black (one
dose of new gold and one dose of dark) has a slight
bronze cast on the body and evident vertical bars.
Crossing two of these blacks resulted in an F2
consisting of 62 new gold and 200 black, no black
lace or wild-type. Also a new gold female and black
male (whose parents were new gold and true black)
gave 214 black and 207 new gold offspring. Thus the
gene for dark (D) and new gold (dng) behave as
Black Angel. (1 dose of dark and 1 dose of new
Black lace were obtained by mating true black and
Hong Kong gold. These black lace, which carried the
recessive gene for Hong Kong gold (see
Part 2), produced an F2 of 29 wild-type, 49
black lace, 12 black, 4 Hong Kong gold. It is
concluded that the genes for dark (D) and Hong Kong
gold (hg) are not alleles since some wild-type
offspring were produced.
Numerous blushing marble were obtained from a
blushing crossed with a fish that had one dose each
of stripeless and marble (having come from a
blushing x marble cross). Since a blushing marble
would have to have one gene for marble and two genes
for stripeless, it is deduced that the genes for
stripeless (S) and marble (Dm) are not alleles.
A smokey female, crossed with a male having one
dose of marble, produced 79 wild-type, 157 marble,
86 smokey. Some of the marbles were suspected of
having one dose of smokey because they exhibited one
or more of these smokey features: (1) black mouth,
(2) black-tipped dorsal fin, (3) gray in the white
streaks in the outer part of the caudal fin.
Two such males were tested for smokey by mating
them to wild-type females. This produced: male #1:
126 wild-type, 269 marble, 123 smokey; male #2: 27
wild-type, 47 marble, 21 smokey. Not only was smokey
present in the tested marble males but the genes for
marble (Dm) and smokey (Sm) did not act as alleles
since the crosses produced some wild-type offspring.
A male having one dose each of marble, zebra and
smokey was mated to a wild-type female, producing 37
wild-type, 136 marble (including marble with zebra
and/or smokey), 34 zebra, and 59 smokey (including
zebra-smokey). Zebra-smokey looks like zebra until
the stripes disappear as the smokey pattern
develops. Since there were wild-type offspring, it
is concluded that the genes for marble (Dm) and
zebra (Sze) are not alleles.
A marble female was mated to a new gold male,
producing 241 wild-type and 217 marble. One of the
marble F1 males, mated to a new gold female,
produced 105 marble and 111 new gold. Since no
wild-type offspring were produced, it is concluded
that the genes for marble (Dm) and new gold (dng)
act as alleles.
1 dose of marble and 1 dose of new gold.
Since (1) the genes for dark and marble behave as
alleles, and (2) the genes for dark and Hong Kong
gold do not act as alleles, it follows that the
genes for marble (Dm) and Hong Kong gold (hg) are
A smokey male was tested and found to have one
dose of stripeless since, when mated to a wild-type
female, he produced wild-type, smokey and stripeless
offspring. Since there were some wild-type
offspring, it is concluded that the genes for smokey
(Sm) and stripeless (S) are not alleles.
A female with one dose of zebra, mated to a
blushing male, produced all stripeless offspring,
some of which had more black blotches on the body
than I had ever seen on fish with one dose of
stripeless but without zebra. When the ones with
increased splotching matured, their dorsal fins had
an number of light-colored horizontal bars (compared
with wild-type), a zebra characteristic. One of
these that was suspected of having one dose each of
zebra and stripeless was tested by mating him to a
wild-type female. From the results, 188 stripeless
and 220 zebra, it is concluded that the tested fish
did have one dose each of stripeless (S) and zebra (Sze)
and that these genes behave as alleles.
A blushing female, mated to a Hong Kong gold
male, produced 100% stripeless, non-gold offspring.
The F2 included some each of blushing, Hong Kong
gold blushing, stripeless, Hong Kong gold and
wild-type. It is concluded that the genes for
stripeless (S) and Hong Kong gold (hg) are not
alleles, since wild-type appeared in the F2 and
since Hong Kong gold blushing would have to have two
doses each of Hong Kong gold and stripeless.
Since (1) stripeless and zebra act as alleles,
then it follows that the genes for smokey (Sm) and
zebra (Sze) are not alleles.
A smokey female x new gold male produced smokey
and wild-type offspring. One of the F1 smokey males
was mated to a new gold female, giving 91 wild-type,
80 smokey, and 156 new gold. This fits the expected
ratio (1 wild-type, 1 smokey: 2 new gold), if the
smokey pattern is not expressed in a fish having two
doses of new gold. Therefore, half of the 156 new
golds were assumed to carry the gene for smokey.
Further evidence that new gold, in double dose,
blocks development of the smokey pattern was
obtained by mating smokey parents, both of which
came from a smokey female and new gold male. These
produced 71 smokey, 33 chocolate (double dose smokey,
Part 1), 42 new gold, 32 wild-type. These
numbers fit the expected ratio (6 smokey: 3
chocolate: 4 new gold: 3 wild-type), if the smokey
pattern is not expressed in the presence of
double-dose new gold. Since each of the spawns (from
smokey male carrying new gold x new gold female, and
from smokey parents each having one dose of new
gold) produced some wild-type offspring, it is
concluded that the genes for smokey (Sm) and new
gold (dng) are not alleles.
Since (1) zebra and stripeless behave as alleles
and (2) stripeless and Hong Kong gold are not
alleles, it is deduced that the genes for zebra (Sze)
and Hong Kong gold (hg) are not alleles.