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Home Q & A Board Biology-Related Homework Help Genetics and Developmental Biology
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cashboxz01 cashboxz01
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11 years ago
Is there a clear algorithm of determining genotypes of parents given a pool of progenic data.

Question in the book:
A wild-type male and a wild-type female Drosophila with red eyes and full wings are crossed. Their progeny are shown below:

Males
3/8 full wing, red eye
3/8 miniature wing, red eye
1/8 purple eye, full wing
1/8 miniature wing, purple eye

Females
3/4 full wing, red eye
1/4 purple eye, full wing

a. Using clearly defined allele symbols of your choice, give the genotype of each parent.
b. What is/are the genotypes of females with purple eyes? Of males with purple eye and miniature wings?



My answer:

a) since all daughters are W+ , the father must be W+Y
and 3:1 on R so father must be R+r-

Mindf*cked when trying to figure out genotype for mother

b) This seems pretty simple, as 1/4 are red eyed, then it must be r-r-/W+W+ or r-r-/W+w-
Although, I'm not exactly sure if this is the right way to do this

If someone could provide a clear methodology of solving these types of problems, it would be appreciated. We have to suffer with the worst textbook in the world.
Source  Genetic Analysis, Mark Sanders, 1st ed
Read 2595 times
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wrote...
#1
11 years ago
Combine your phenotypes. Its going to be easier that way. Will assist when you've done that (studying for my own midterm lol)
Post Merge: 11 years ago

Also, there's no "algorithm". You know your sh@# or you don't and you need to be able to recognize patterns and ratios which lead to gene interactions. Imagine this with 3 gene and 6 gene crosses LOL
cashboxz01 Author
wrote...
#2
11 years ago
Quote from: Alpha (11 years ago)
Combine your phenotypes. Its going to be easier that way. Will assist when you've done that (studying for my own midterm lol)
Post Merge: 11 years ago

Also, there's no "algorithm". You know your **** or you don't and you need to be able to recognize patterns and ratios which lead to gene interactions. Imagine this with 3 gene and 6 gene crosses LOL

So how exactly do I combine my phenotypes? This is extremely frustrating since my textbook doesn't even show how to do that.
wrote...
#3
11 years ago Edited: 11 years ago, Alpha
Also, are those the exact words from the textbook? Check the question.
Ratios seem off unless my counting is that bad.

2 genes involved, one for color, one for wings. Parents are het for color because it gives a 3:1 ratio. 2:1 ratio produced for wing type which doesn't exist as far as I know unless you have lethal alleles involved. For questions like this, you want to look at each gene separately, as you would in a monohybrid cross or single gene cross.
Post Merge: 11 years ago

Quote from: cashboxz01 (11 years ago)
Quote from: Alpha (11 years ago)
Combine your phenotypes. Its going to be easier that way. Will assist when you've done that (studying for my own midterm lol)
Post Merge: 11 years ago

Also, there's no "algorithm". You know your **** or you don't and you need to be able to recognize patterns and ratios which lead to gene interactions. Imagine this with 3 gene and 6 gene crosses LOL

So how exactly do I combine my phenotypes? This is extremely frustrating since my textbook doesn't even show how to do that.

Hey there, basic math. You have 12 offspring if they are not gender separated. Add up the totals of each phenotype.
Post Merge: 11 years ago

You are what I need to help me study! Face with Stuck-out Tongue

6/12 full red.
2/12 full purple
3/12 mini red
1/12 mini purple.

8 full:4mini (reduce)
9 red: 3 purple (reduce)
cashboxz01 Author
wrote...
#4
11 years ago
Quote from: Alpha (11 years ago)
Also, are those the exact words from the textbook? Check the question.
Ratios seem off unless my counting is that bad.

2 genes involved, one for color, one for wings. Parents are het for color because it gives a 3:1 ratio. 2:1 ratio produced for wing type which doesn't exist as far as I know unless you have lethal alleles involved. For questions like this, you want to look at each gene separately, as you would in a monohybrid cross or single gene cross.
Post Merge: 11 years ago

Quote from: cashboxz01 (11 years ago)
Quote from: Alpha (11 years ago)
Combine your phenotypes. Its going to be easier that way. Will assist when you've done that (studying for my own midterm lol)
Post Merge: 11 years ago

Also, there's no "algorithm". You know your **** or you don't and you need to be able to recognize patterns and ratios which lead to gene interactions. Imagine this with 3 gene and 6 gene crosses LOL

So how exactly do I combine my phenotypes? This is extremely frustrating since my textbook doesn't even show how to do that.

Hey there, basic math. You have 12 offspring if they are not gender separated. Add up the totals of each phenotype.
Post Merge: 11 years ago

You are what I need to help me study! Face with Stuck-out Tongue

6/12 full red.
2/12 full purple
3/12 mini red
1/12 mini purple.

8 full:4mini (reduce)
9 red: 3 purple (reduce)

So 2:1 is full wings
and 3:1 is red

That could mean that red is dominant and wings are dominant(based on my guesstimate)
What would be the next step?
wrote...
#5
11 years ago Edited: 11 years ago, Alpha
My advice now is to reread the question ASAP and make sure you copied the correct information and all details, DO NOT abbreviate or shorten the textbook question.
Post Merge: 11 years ago

Red IS dominant. What are you allele symbols and alleles for both genes. Post them for me.
What are the genotypes that will give you a 3:1 phenotypic ratio?
You now have part of your parental genotype. Do the second one the same way but I can tell you now that there isn't a cross that makes a 2:1 ratio unless there are lethals. Check the question.
cashboxz01 Author
wrote...
#6
11 years ago
Quote from: Alpha (11 years ago)
symbols

I re-read it, and yes, that is the same question word-for-word from my stupid text.

What are the genotypes that will give you a 3:1 phenotypic ratio?
I would say heterozygous, which is R+r-

You now have part of your parental genotype. Do the second one the same way but I can tell you now that there isn't a cross that makes a 2:1 ratio unless there are lethals.

I'm guesstimating that the 2:1 ratio is from the father being W+Y. This leaves the male offspring, from which there is a 4:4 ratio, which is 1:1 in reality. If the father is proven W+Y, then the mother must be w-w- if there are any kids to have mini-wings. The sons could theoretically have w-Y. But in this case, they should then be 1:2 instead of 1:1 . Dammit :-/


This is beyond ridiculous that I have to spend hours doing a single problem for this class. The author of this textbook needs to burn in hell. Seriously, if I don't approve this text, how on earth does the author expect chuck norris to approve it?
wrote...
#7
11 years ago
I can't help you until you define your allele symbols for me.
cashboxz01 Author
wrote...
#8
11 years ago
Quote from: Alpha (11 years ago)
I can't help you until you define your allele symbols for me.

W+W+ and W+w- are for full winged
w-w- is for mini winged

R+R+ and R+r- for red eyed
r-r- is for purple eyed
wrote...
#9
11 years ago
Quote from: cashboxz01 (11 years ago)
Quote from: Alpha (11 years ago)
I can't help you until you define your allele symbols for me.

W+W+ and W+w- are for full winged
w-w- is for mini winged

R+R+ and R+r- for red eyed
r-r- is for purple eyed

You need to start with the basics. That's not how you define allele symbols. Those are not allele symbols, those are genotypes.

Try again.
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