genotypes

[colorin]

now, one of my pairs (cock: red head, green back, purple chest and hen: black head, green back and purple chest) have two chicks, and one looks "normal" but the other is growing pale feathers (yellow back?)
IThis means that either the cock or the hen -or both- have the "yellow back" in thir genes or... that the "father" of this chick was the yellow back I had (now dead) that was paired to another hen! :-O

[colorin]

sorry, I made a mistake. The cock is definitely a diluted one, as the ring around his face is not black but sort of blue/greyish. So, that's why the chick has come out yellow.
This is the cock:

[natamambo]

Yep, cock is a SF Yellow back, nice looking bird. YB chick is a hen!

[colorin]

a hen? how do you know?
Learning about genetics is more difficult than I thought!! Sometimes I get lost in between so many BF SF and so...

[Diane]

Some mutations are sex linked.
The best way I found to get a handle on genetics, is read, read, read.
I also found the genetic forecasters really helpful. You put in the colours of the parents and the colour of the expected young is displayed for you.
These forecasters can be either used on line
http://www.amadinagouldove.cz/gouldian- ... /index.php
or downloaded to your computer to be able to use off line too.
http://www.ladygouldianfinch.com/features_software.mgi

I find its useful also to be able to find out the colours of the parent birds by looking at the colours the young turn out and working backwards. Ideal if you aren't sure of the colour heritage of your birds.
Bear in mind with these forecasters they work on percentages.

[natamambo]

a hen? how do you know?
Learning about genetics is more difficult than I thought!! Sometimes I get lost in between so many BF SF and so...

The YB gene works in pairs and is on the same chromosome set as the one that determines sex. Birds are opposite to human, the male has two matching chromosomes (XX except it's described as WW) and the female non-matching (ZW). Unlike humans (where the sperm determines sex) the egg determines sex being either a male producing egg (with a W chromosome) or a female producing egg (with a a Z chromosome).

If the cock has the YB gene on both Ws then he is a full yellow back (hence double factor, DF). If he has the YB gene on only one W then he is SF, the gene is co-dominant with normal so each works a little bit resulting in your bird (ie yelowish green and blue-grey blacks). However the hen can only ever have the YB gene on one W chromosome and therefore she is automatically a YB as she can never be a "dilute".

Your cock can produce (on average) when paired with a normal hen 50% normal males (who get the normal gene from both mum and dad), 50% YB SF males (who get the normal off mum and the YB off dad), 50% normal females (they got the W off dad that had the normal gene) and 50% YB females (coz they got the "other" chromosome). As a SF male cannot produce a DF YB male any chicks that are yellow will be hens, no need to wait for the first moult.

A YB cock can never produce YB DF cocks unless it is paired with a YB hen as the young need the other chromosome with the YB gene from mum. Some say there is a lethal factor to this combination (DF YB and YB) and the young will die in the nest. I have just started in Gouldians (got my first one two weeks ago and was hooked because of the genetics) so I now have (from different sources to ensure mixed bloodlines) three YB cocks, one YB hen and two normal hens, designed to give me all YB hens and a selection of DF and SF YB cocks to use as the basis for a breeding program moving forward.

[colorin]

thanks for your help. Ithink I finally understand head colours and chest colours, but backs seem to be more complicated.
I guess I will be able to trace back my gouldians genes based on the chicks they produce.
In theory this yellow chick will be purple (or lilac?) chest, and red headed...
Well, I have no yellows, so it's a good reason to keep her

[monotwine]

25% Male >> Red / Black (Head) - Purple (Chest) - SF Yellow (Body)
25% Male >> Red / Black (Head) - Purple (Chest) - Green (Body)
25% Female >> Red (Head) - Purple (Chest) - Yellow (Body)
25% Female >> Red (Head) - Purple (Chest) - Green (Body)

The above is the results from your pairing: the Gouldian Forecaster you can download from the net for free by Carlos Matos. Seems you can have a male SF yellow (dilute) and only a yellow in hens, all other babies should be normals.
Breast colours should all be purple as its the most dominant as I understand it. Perhaps there is a small percentage of another colour if your birds are split to anything, but I doubt it unless they are both say split to White breast.

Your male is beautiful. I can only hope my dilute boy looks half as good.
Fun when you get something unexpected in the nest. Congrats.

[colorin]

ok, these are the two chicks from that pair that have fledged today. The yellow hen and her brother/sister:

I hope they go back to the nest tonight (it will be warmer there)

[Diane]

They probably wont go back into the nest