There are many genetic myths that have been perpetuated
throughout the cage bird community as facts while in reality, they have no
genetic basis what so ever. As a geneticist, I would like to outline why some of
these statements are false and give supporting information. You may decide to
accept my explanations or continue believing what you have been told. I am just
trying to provide some information so that people can make informed decisions.
GENETIC MYTH #1
Breeding 2 colour mutation birds together will result in
unhealthy, weak, and smaller chicks: FALSE - This one really confuses
geneticists when you tell them that people believe this. A colour mutation
normally occurs in only ONE gene, a colour gene (or several colour genes if
they are linked). Colour genes are what they sound like, responsible for the
colour pigments of the feathers. They have no effect on fertility or size of
the bird. To say that 2 colour mutation birds will produce small unhealthy
chicks is equivalent to saying that 2 humans with the same one trait will
experience the same problems. Most of us know that this does not happen.
However, if these 2 individuals are related, you can get weak unhealthy
offspring. Inbreeding is the most likely culprit of the problems thought to be
associated with breeding 2 colour mutations together. The classic signs of
inbreeding in birds are infertility, mental retardation, physical birth
defects, an increase in homozygous recessive traits (genetic disorders and
colour mutations), death of the chicks while they are still in the egg, death
of the chicks shortly after they hatch, weak chicks, and growth retarded birds.
Since most colour mutations are derived from one or a few highly inbred birds,
the making of Splits and breeding of colour mutations to Splits is needed to
create a diverse unrelated population. Once you get to a certain point and keep
splitting highly unrelated birds, it loses all usefulness. As long as you are
breeding unrelated birds together, no matter what colour they are, you should
get large healthy chicks (*DISCLAIMER* there are genetic disorders that will
pop up in any unrelated population and will effect a certain percentage of the
offspring no matter what you do). If you breed two unrelated Blue birds and
keep breeding them to unrelated Blues, you will have few problems (remember
disclaimer). The problem is that many people do not breed unrelated birds
together because they line breed, won't bring in new stock, or just don't care
(which is unfortunate, but is true in some cases). Also, many people believe
that just because a bird is Green, it will be more unrelated to their Blue bird
than a Blue bird from another population. This may be true sometimes, but not
all of the time. There are many Splits sold as Greens (which are virtually
impossible to track) and some Green birds may be close genetically to a Blue
bird strictly by chance.
GENETIC MYTH #2
Colour Mutation Genes are Lethal Genes: FALSE. This is one
of the reasons that people give to not breed two birds of the same mutation
together. As stated above, a colour mutation normally occurs in only ONE gene,
a colour gene and this gene is normally nonessential (for example: albinos).
Albinos are not producing any (or much) melanin. This is commonly because the
gene is either lost or messed up (to put it in non-genetics terms). If the gene
is not functioning or functioning properly, as in the albino case, and the
animal is still alive and/or healthy, this proves that the colour gene has no
effect on the animal's survivability. There may be a few rare cases where two
copies of a gene with a colour mutation is lethal. This would most likely be
due to 1. The loss of the entire chromosome which holds the colour gene. A
chromosome has many genes on it and one or several of those genes may be
essential to life. If they are present only in one copy (normally there would
be two copies), the effect may be lethal. 2. Part of the colour gene recombines
with another gene essential for life. Since the essential gene has been
disrupted, it is unlikely to produce a product and the effect may be lethal. 3.
A few other rare recombination, transversion, or translocation events that are
too complicated to explain. In a nutshell, colour mutation genes are not lethal
in the homozygous form, except for a few possible rare cases.
GENETIC MYTH #3
Colour Mutations are the result of a single recessive
mutation: YES in some cases and NO in some cases. This is where it gets quite
complicated. If you are interested in this topic, I'd suggest you read the
Complex Inheritance topic on this web site.