Page Title

ORIGINAL
BOOK REVIEW
by
Dr. Rainer R.
Erhardt
"Well, there is help on
the horizon and
anyone seriously
interested in color
genetics should take a
look at Linda Rubin's
book: COCKATIEL
G ENETICS MADE EASY!
Though this book is
primarily directed to
breeders of cockatiel
mutations, there is
enough information in
this little volume to
teach anyone the
secrets of dealing
with recessive,
sex-linked, and
dominant mutations..."
ACBM, Vol. 65, No.12
CLICK TO READ THE
REST OF THE REVIEW!
112 pages, 15 chapters,
glossary & more!

Multiple Bird
Households
by Linda S.
Rubin

Ultimate
Parrot Guide
by Linda S.
Rubin

click for descriptions, chapter excerpts, & reviews!

Series by
Linda S. Rubin

Crossover in a Yellowcheek Cinnamon-Pearl Pied Hen
Copyright 2004 LINDA S. RUBIN
CF Genetics Consultant/Panel Judge
“All Rights Reserved”
Adapted from "My Mailbox"

QUESTION
Hi Linda,

I've asked you questions in the past and you were a great help. When
you have some time could you look at this match for me? I do not have
the pedigrees on this pair; I only know what I've stated below. I'm
questioning the sex of the chicks. I have a Cinnamon- Pearl split Pied
hen and a Normal Pied male split to sex linked Yellowcheek. I was told
the hen was split to Yellowcheek when I purchased her, however, I know
she can't be split to sex-linked Yellowcheek. Could she possibly be split
to Dominant Yellowcheek? The babies are as follows:

Yellowcheek Cinnamon Pearl Pied - hen? (Would this prove the father is
also split    Cinnamon)?
Yellowcheek split Pied - hen?
Yellowcheek Pied - hen?
Normal Grey split Pied - male?

Please let me know what you think about this ... thanks so much!
Kim

ANSWER
Hi Kim,

From the information you've provided and the chicks you produced you
have a:

Pied/split Yellowcheek Cinnamon-Pearl cock:
XCP   XY - pp
and a Cinnamon Pearl split/Pied hen:
XCP   Y   - np

Notice the hyphens between C-P (Cinnamon-Pearl) below are intended
because they are inherited together on the same male X chromosome.
(The hyphen shown above preceding "pp" or "np" merely illustrates the
separation of the recessive mutations that follow as we write them in
shorthand script).

Under normal circumstances your pair would produce the following:

Cocks:
12.5% Cinnamon-Pearl Pied
12.5% Cinnamon-Pearl/split Pied
12.5% Pied/split Yellowcheek Cinnamon-Pearl
12.5% Normal Grey/split Yellowcheek Cinnamon-Pearl Pied
Hens:
12.5% Cinnamon-Pearl Pied
12.5% Cinnamon-Pearl/split Pied
12.5% Yellowcheek Pied
12.5% Yellowcheek/split Pied
-------------
100%

However, because you produced a Yellowcheek Cinnamon-Pearl Pied
hen, we know that a rare occurrence of crossover has occurred. In this
case, your cock bird switched chromatids (one "leg" of an X male sex
chromosome) with another chromotid from his other X male sex
chromosome. Therefore, XCP XY becomes: XCPY X. In other words, the
gene for Yellowcheek "crossed over" to join the X chromosome carrying
Cinnamon-Pearl.

The new gametes from crossover now present another chart of
possibilities:
XCPY X - pp       = cock (sire)
XCP    Y - np       = hen   (dam)

This occurrence of crossover would produce the following offspring:

Cocks:
12.5% Cinnamon-Pearl Pied/split Yellowcheek
12.5% Cinnamon-Pearl/split Yellowcheek Pied
12.5% Pied/split Cinnamon-Pearl
12.5% Normal Grey/split Cinnamon-Pearl Pied
Hens:
12.5% Yellowcheek Cinnamon-Pearl Pied
12.5% Yellowcheek Cinnamon-Pearl/split Pied
12.5% Pied
12.5% Normal Grey split Pied
-----------
100%

As you will note from the crossover expectations, this is where we find
the Yellowcheek Cinnamon-Pearl Pied hen.

We also know that both the Yellowcheek Pied and the Yellowcheek/split
Pied are hens. The Normal Grey under expected conditions would be a
Normal Grey/split to Yellowcheek Cinnamon-Pearl Pied cock; or under
crossover conditions it could be a Normal Grey/split Cinnamon-Pearl
Pied cock or Normal Grey/split Pied hen. On the latter, you would need
to wait to see if you have a hen - or if male, you would need to test breed
in order to learn which colors it carries as a split in a heterozygous state.

Should you produce any other genotypes such as visual Cinnamons or
visual Pearls, it merely suggests another variation of crossover (e.g.
where Cinnamon separates from its link with Pearl), which I can easily
diagram for you if needed.

The sex-linked variety of Yellowcheek can only be carried as a split in
males; females can never be split to sex-linked mutations. Neither is your
female split to Dominant Yellowcheek, because a dominant mutation is
ALWAYS visible; a dominant color can never be hidden or carried as a
split in either male or female cockatiels.