This weeks question on genitics. (Senior Scientific)

[Mellifera Crofter]

Kitta, you are right about yellow being recessive in reality....but in the fictitious world of the question it states a heterozygous yellow eyed queen, so for the sake of the question Y (yellow) must be dominant.

Thanks Thymallus. You’re right. I probably would have answered it as with Y dominant, and then explained why the question is wrong in attributing Yellow as dominant.


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[Thymallus]

The question is clear! 30% of all of the drones that mate with the queen.

In the pressurized situation of a timed examination the question could be perhaps wrongly interpreted as referring to the offspring of only the 30% brown eyed drones. Better perhaps to state , for example, queen mated with 10 drones, 3 of which were brown eyed and 7 of which were yellow....this removes any ambiguity for the person answering the question....except as Kitta points out that yellow eyes are recessive not dominant in the real world

[Jon]

Yellow abdomen colour is actually dominant over black in spite of what the majority of beekeepers appear to believe. It is a polygenic trait controlled by a complicated mixture of 3 major genes and several modifying genes.
There is a previous thread on this site from several years ago.
This paper by Woyke discusses the genetics.

http://jerzy_woyke.users.sggw.pl/1977_hered_color.pdf

[Mellifera Crofter]

Yellow abdomen colour is actually dominant over black in spite of what the majority of beekeepers appear to believe. It is a polygenic trait controlled by a complicated mixture of 3 major genes and several modifying genes. ...

Thanks Jon. Now it's getting really complicated - for me, anyway. The follow-up generations of Murray's imported bees are getting darker - so, it must be a complicated soup of genes at work there.
Kitta

[gavin]

Just feel that I should congratulate Jane S on being spot on in every way. The question was good, and brown eyes (in this hypothetical example) come with yy which is at a frequency of 0.15 (15%) in the cross.

I do these things with proportions.

Gametes from the heterozygous female:

Y - 0.5 (lets say gamete i)
y - 0.5 (gamete ii)

Gametes from the drones:

Y - 0.7 (gamete iii)
y - 0.3 (gamete iv)

The combinations and proportions after fusion of the gametes at random are:

i x iii ie 0.5 x 0.7 = 0.35 as YY
i x iv ie 0.5 x 0.3 = 0.15 as Yy
ii x iii ie 0.5 x 0.7 = 0.35 as Yy
ii x iv ie 0.5 x 0.3 = 0.15 as yy

As Jane says, that is easier in a table of female x male gametes.

Only yy are brown eyed and they are at 0.15 or 15%. The rest (85%) are yellow-eyed.

As a check add up the proportions and they come to 1.0.

[prakel]

The follow-up generations of Murray's imported bees are getting darker - so, it must be a complicated soup of genes at work there.
Kitta

I think that it must be time for some follow up research on that done by Woyke and, previously, Roberts. No one's questioning their results but there's clearly a different result in practice -which those of us that have tried to maintain orange colouration have seen constantly. No question that the population tends to shift towards a darker type.

[Jane S]

Why, thank you!
Exam questions are meant to test your knowledge (on basic genetics, in this case) and your application of that knowledge. Exam candidates need to have that knowledge and be able to apply it, using the information in the question. Examiners could have used any colour, not just brown and yellow, to test this knowledge, or any other characteristic where there are two distinct different types. This basic genetics can be applied to anything, not just bees.

"Assume that bees have just two eye colours, yellow denoted by Y and brown denoted by y. If 30% of the drones that mate with a heterozygous yellow eyed queen are brown eyed drones . . . ": if there are only two eye colours and you have 30% of one colour - the inference is that the rest, 70%, are the other colour.
If the question had asked for a comment on your observations, then add it, but otherwise your comment would be wasted.

But Jon is right - in reality, any colour characteristic is determined by many genes operating together - a complicated soup indeed!

[Greengage]

Do you ever feel "I am sorry I started this"

[gavin]

Do you ever feel "I am sorry I started this"

Lol! Post #8 did looks like: 'OK. I've had enough now'!

But you are learning, right? If not, we can clarify!

G.

[Greengage]

Yes very enjoyable thanks, for all the info, some knowledgeable beekeepers on here, This is one of the better sites and because its a forum with topics people usually stick to it. Appreciate the answers.