This weeks question on genitics. (Senior Scientific)

[Greengage]

I am just no god at these questions. (b)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 determine the percent of each genotype and phenotype of their offspring. (14 marks)

[Thymallus]

Devil is the detail....to me their is ambiguity in whether they are simply asking for the off spring of the 30% drones (y) (inferred by asking for details of their progeny) or the whole 100% that the queen mated with...which would be unfair as they don't give any details of the remaining 70% of the drones, although you could infer that they were Y (yellow) as only other thing they could be.
So for 10 offspring with the first 3 drones (30%) y mated with queen Yy.
1. Yy
2. yy
3. 50% chance of Yy or yy for the third offspring....so need to do a twenty offspring.

However you look at it this comes out at 50%Yy and 50%yy

Assuming other drones are Y x Yy queen
4. YY
5.YY
6.YY
7 Yy
8. Yy
9.Yy
10 50% Chance of being Yy or YY

and if you work out the phenotype I make it 80% are yellow eyed.

Hope that is of some small help and not too confusing.

[Greengage]

I had to do a bit of work and figure out the meaning of terms.
Genes account for variation in inherited characteristics.
Allele are an alternative form of the same gene where a number of different types of the same gene exist.
Homozygous: Both Alleles are the same.
Heterozygous: Two alleles are different.
Gamete: is a haploid sex cell.
Dominance: One Allele masks the effects of the other allele.
Recessive: The Alleles effect is only expressed when both Alleles are the same. (Homozygous)
Haploid: is a term used when a cell has half the number of chromosomes.(Drones)
Diploid: is a term used to describes a cell with two sets of chromosomes. (Workers and Queen)
Genotype: Genetic make up of an individual.
Phenotype: physical make up of an individual.

Alleles/ Homozygous/ Heterozygous/Dominance/ Recessive.
There can be a number of different Alleles controlling the same characteristics such as eye colour in humans Blue, Green and Brown.

Here we are looking at honey bee eyes.
Each Insect Drone/Queen has a maximum of two alleles for each characteristic for example a bee with black eyes could have two black eye alleles or one black eye allele and one white eye allele.
Alleles are usually assigned letters with a capital letter signifying a dominant Allele and a lower case letter signifying a recessive Allele. B (Dominant)Brown eyes b (Recessive) White eyes.
BB is described as Homozygous dominant.
Bb is described as Heterozygous.
bb is described a Homozygous recessive.

A genetic cross is a table showing how characteristics are inherited.

Then I wrote out the question again as I thought it a bit of tongue twister.

(b) 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 determine the percent of each genotype and phenotype of their offspring. (14 marks)

Assume that bees have just two eye colours, yellow denoted by Y (Dominant)and brown denoted by y (Recessive). If 30% of the drones that mate with a heterozygous (Both Alleles the same) yellow eyed queen are brown eyed drones determine the percent of each genotype (genetic make up of individuals)and phenotype ( physical make up of individuals) of their offspring. (14 marks)

I cannot disagree with your answer as I don't know enough but will have a go when I get my head around it. Thanks for looking at it.

[Mellifera Crofter]

Can one have a heterozygous yellow-eyed queen? I thought yellow is recessive - so, if she is heterozygous, she must be Yy - and that is brown.
Or am I making a fool of myself now?
Kitta

[Thymallus]

she must be Yy - and that is brown.

Usual nomenclature is that capital letters represent the dominant allele and the question states capital Y is yellow, meaning Yy will be be Yellow. Drones only have one allele (as haploid) so if brown they are all lower case y.
It's very badly phrased question...shoot the examiner.

[Jane S]

I am just no god at these questions. (b)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 determine the percent of each genotype and phenotype of their offspring. (14 marks)

The question is clear! 30% of all of the drones that mate with the queen.
Always, (genetics convention dictates) a capital Y means it is the dominant allele: and conversely, a lower case letter - ie y means the recessive allele. (This might not be the case in real life, but if you are trying to work out the genetics question you have to go with the information they give you!)

So - a heterozygous yellow-eyed queen has a genotype Yy. She mates with 30% brown-eyed drones, whose genotypes are y and 70% of the drones are yellow-eyed and their genotype is Y.
The queen produces eggs - half are Y and half are y.

You can work out which eggs are fertilised by the sperm from the two different drones. This is best done by producing a table :
Queen eggs  Y y
drones 3y 3Yy 3yy
7Y 7YY 7Yy (Sorry table doesn't come out too well!)

Take the queen eggs with Y in the second-from-right column – they can be fertilised by 3y sperm to give 3Yy females. And they can be fertilised by 7Y sperm to give 7YY females.
Take the queen eggs with y in the last column – they can be fertilised by 3y sperm to give 3yy females. And they can be fertilised by 7Y sperm to give 7Yy females.
Taking the numbers from the table and the genotypes –
7YY : 10Yy : 3yy
For every 20 fertilised eggs (7/20) x 100 = 35% are YY
(10/20) x 100 = 50% are Yy
(3/20) x 100 = 15% are yy
Phenotype refers to how the characteristic appears – yellow- or brown-eyed.
Only yy are brown-eyed, so that’s 15%.
YY and Yy are yellow-eyed, so that is all the rest, 35 + 50, ie 85%.
Hope that helps.

[Mellifera Crofter]

Usual nomenclature is that capital letters represent the dominant allele and the question states capital Y is yellow, meaning Yy will be be Yellow. Drones only have one allele (as haploid) so if brown they are all lower case y.
It's very badly phrased question...shoot the examiner.

Yes, shoot the examiner. I understand the convention that the uppercase letter is dominant - but in this case it is wrong. Yellow is recessive, so yellow cannot be capital Y, and she can't be Yy. As I understood it, Dzierzen used Italian bees to prove parthenogenesis precisely because yellow is recessive (using cordovans). Or are there cases where yellow isn't recessive?
Kitta

[Greengage]

Thanks for the interest in this topic.

[Mellifera Crofter]

Ps: anyway, if I pretend the queen is yellow-bodied rather than yellow-eyed, I agree with Jane’s answer.

But that might be wrong too. I think yellow-bodied is also recessive, which is why C4U told us imported bees soon revert to dark bees).


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[Thymallus]

Yes, shoot the examiner. I understand the convention that the uppercase letter is dominant - but in this case it is wrong. Yellow is recessive, so yellow cannot be capital Y, and she can't be Yy. As I
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.

[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.

[Mellifera Crofter]

... 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. .... If the question had asked for a comment on your observations, then add it, but otherwise your comment would be wasted. ...

Yes, you're probably right, particularly with this question - but sometimes I've thought they're trying to trick us!

For example, in the March 2017 Module 8 exam, there was a short two point question (so, no big deal in terms of marks): 'What should be added to pollen to make a pollen substitute patty?' After I've wasted my two-point-worth of time answering what to use to make a pollen substitute patty, or perhaps what to add to pollen to make a pollen patty (I can't remember), I realised the question is bollocks, and then got flustered and wasted two more points of time explaining why the question doesn't make sense.

I think I've come across other examples - but I can't remember them now.
Kitta