What's a recessive gene?

[JustAChickenLoverOverHere]

Primary reason for using "recessive" and "dominant" terms is to describe one particular trait. Simple explanation is as follows:

1) A chick receives half it's DNA from mom and half it's DNA from dad.
2) A chick needs to receive TWO copies of a recessive gene for that recessive gene to be "visual" or "express" on that chick - that means they need to receive one copy from mom and one from dad.
3) If a chick only receives ONE copy of a recessive gene (so from one parent only) then they carry that one gene but it is "non visual" or "not expressed" on that chick. We often call that "being split to that recessive trait" - i.e. "split to/for lavender".

The secondary reason for using "recessive" and "dominant" terms is to describe the "heirarchy" or "order" in which multiple traits show on a bird.

For example Colour A might be considered "dominant" over Colour B. Or alternatively that Colour B is "recessive" to Colour A. So even though your chick might be genetically expressing both colours - Colour A is the only one you see and Colour B is hidden.

Thank you! That example of "split to lavender" gave me a great understanding of a hidden(/single?) recessive gene. So, if a chick has one copy of a recessive gene, it carries that gene and can give the second copy of it if the other bird has the recessive gene?

 

[sourland]

Thanks everybody! And you were right Jade, visuals do help! I've seen Punnet squares before with colors like B and b (lowercase and uppercase), and I thought it was just the initial for the color, but if I understand correctly, uppercase is dominant and lowercase is recessive? Please correct me if I'm wrong anybody!

You got it!

 

[JustAChickenLoverOverHere]

You got it!

Thank you sourland!

 

[DarJones]

While dominant and recessive are the extremes, there is a third condition called penetrant where two different genes are both expressed to some degree. With a dominant and a recessive, one or the other is always expressed. With a penetrant gene pair, you can visually tell both genes are present. My work with Silver Laced Wyandottes suggests that columbian is penetrant. A bird with 2 copies of columbian is single laced. A bird with no copies of columbian is double laced. A bird with 1 copy of columbian has a mix of single and double laced feathers and every variation in between.

 

[The Kooky Kiwi]

Thank you! That example of "split to lavender" gave me a great understanding of a hidden(/single?) recessive gene. So, if a chick has one copy of a recessive gene, it carries that gene and can give the second copy of it if the other bird has the recessive gene?

Yes Here's a very simplified example of that for you. Let's say you have two birds who are "split" for Lavender. So they look some other colour but you know they are carrying one lavender gene hidden. They can still pass those genes down to their chicks .. and if this results in a chick receiving two copies then that chick will be "visual" for lavender.

This is why recessive genes that are carried invisibly as "splits" can be such a devil! If you cannot see them you don't always know they are there. You are breeding your birds based on the colours you can see and then BAM - out of the blue an unexpected colour or pattern comes out - and this is a result of those hidden "split" genes being recombined together enough to show visually <3



In this example you end up with 1 in four babies being visual lavender = Cool!

But the other 3 in four babies - we have no way of telling which two carry the hidden Lav gene and which 1 carries no Lav gene.

This is when you will hear people talk about "test breeding" their birds.
I would breed a bird that I "suspect" has one copy of lavender to a bird that is visual lavender (has two genes).
If the "suspect" bird did have one copy then I'd expect to get 50% of the chicks receiving two Lav genes and looking Lav.
If the "suspect" bird did NOT have one copy then I'd expect all the chicks would receive only one Lav gene (from the visual Lav parent only) and therefore all be guaranteed "split to Lavender" babies.