Drosophila and its offspring

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Ok, you can answer this question to the best of your ability in a serious manner, or in a non-serious manner.
In Drosophila, genes a and b are located at positions 22.0 and 42.0 on chromosome 2, and genes c and d are located at positions 10.0 and 25.0 on chromosome 3. A fly homozygous for the wild-type alleles of these four genes was crossed with a fly homozygous for the recessive alleles, and F1 daughters were backcrossed to their quadruply recessive fathers. What offspring would you expect from this backcross, and in what proportions?

[ January 23, 2003, 12:11: Message edited by: Elios ]

 

Low IQ, a few rotten teeth, and a front yard littered with beer cans, shotgun shells, dead pickup truck, and hound dog turds.

Sorry, I went for the physical sciences, not biology.

[ January 23, 2003, 14:45: Message edited by: Rallymama ]

 

Get lost, it depends if the offspring gets born near Chernobil or inside Cloneaid labs.

 

I have absolutely no idea what you're talking about. My eyes haven't glazed over like that since I stopped taking chemistry.

 

Umm... (--o--o--)(2) + (-o--o--)(3), which have alleles a x A -> degenarate to previous allele 4... Oh, hell; it´s something like what Rallymama said. Furry apes... maybe? (Ok, permission to laugh)

[edit] Wait, drosophila´s offspring? I guess it would be a normal, healthy fellow with a risk to have drosophilad offspring.

[ January 28, 2003, 21:03: Message edited by: Virne ]

 

a gay fly

 

Well, it's obvious, isn't it? That's the genetic makeup for Prez. Bushie. Damn, I thought everyone knew that.

 

Serious answers don't seem to be forthcoming! Maybe it's because this topic sounds suspiciously like you're trying to use us to get your homework done!

Don't know much about Drosophila, but I do know about genetics. To answer this question I'll need to know the answers to 2/3 questions:

1) Are the wildtype alleles dominant (ABCD) at each locus? and;
2) What is the relevance of the genetic distances quoted? i.e. whether the genes are far enough apart as to be unlinked (chiasmata occur at high frequencies between loci)

If the answer to the latter question is that they are unlinked then the positonal values are irrelevant and the genes can be treated as separate entities that follow Mendel's laws of segregation.

If the genes are indeed linked then we'll need to know the units for the values that you've provided to get the answers!

 

I think you'd get a dragonfly or a butterfly/moth

 

Like with Lazy Bonzo's Question I hope the basic answer is enough. A lot of information is either irrelevant or missing in your question, making it a bit tricky. Anyway you say the fathers are recessive. If we look at phenotypes we could run into recessive epistasis among other nasty things. Let us save that for later.

The F1 generation
If we start with looking at how the F1 generation is displayed. Let us hope we have simple dominance from one parent (the mother) and the other parent (father) is recessive in all aspects, then we get this cross:
AABBCCDD(mother)X aabbccdd(father)
Capital letters symbolize dominance.
The F1 generation comes out as AaBbCcDd.

Note;
At this point I must make you aware that a wild type allele is not the definition of dominance or not. Wild-type means an allele with a frequence roughly above 1%
*****

F2 generation
So now we cross the Heterozygous F1 generation with the recessive Parent.
AaBbCcDd(F1) X aabbccdd (parent)
We always get abcd from the parent. We always get ABCD Vs abcd in the ratio 1:1 from the F1 generation. The back crossed F2 generation naturally comes out as;
AaBbCcDd
aabbccdd
aaBbCcDd
AabbCcDd
Etc.
The way to calculate it is saying we have two options on each gene. Dominant/recessive. And we have four genes. This yields 2x2x2x2 possible combinations. All coming out in the ratio 1:1. This is the simplest model from your information. The phenotype aspects are impossible to put on any reasonable model. But Since I am not here to make your course work, I have been holding back with my posting for some time. I hope this is sufficient for you.

Phenotypes
Just to make you think about your information if we should make a phenotype model. Would it matter if the recessive parent was a mother? What would be the phenotypic ratio of the flies if Dominant genes of B had dominant epistasis over Aa and aa? Cc cc Dd dd each have their own separate phenotype. Don't answer this but if your thread is your homework, then at least think about it.

Dictionary:
Phenotype: the observed characteristic (red eyes/vs White eyes)
Allele: one form of a single gene. some genes like the immune system related MHC-II has a multitude of different alleles making it much more variable in structure and hence more likely capable of recognizing foreign material.
Homozygous: Both alleles carried for a single gene is alike (AA-aa-BB-bb-CC-cc) the opposite is heterozygous.
Wildtype allele: An allele which has a frequency of roughly 1% and above.
Gene: A distinct segment of DNA. Genes are the blueprint for protein synthesis.
Epistasis the effects of one gene mask or cover up the effects of another gene.

[ January 29, 2003, 17:52: Message edited by: Nobleman ]

 

I took this to the experst, i.e. my sister who is a researcher and gets her doctorate some time this year... Too bad she flunked her finals in genetics while she was in college...

Assuming wild-type = dominant, no linkage, independent assortment, no
cross-over, no mutations, direct mendelian genetics, genes are called
A,
B, C, and D, with dominant designated with capital letters, recessive
with small letters. The offspring will be:
50% Aa, Bb, Cc, Dd
50% aa, bb, cc, dd

BUT... in reality, that scenario does not exist in Drosophila. You
have to take into account the percentage of cross-over based on
distances of genes, as well as the sex of the fly.

More to come as she has more time to calculate more of this...

(A lazy, lazy person... )

 

Awww Arabwel I covered everything. Don't you have faith with me

[ February 01, 2003, 01:31: Message edited by: Nobleman ]