Genetics question drosophila (please help)

[truethat]

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Hi

thank you in advance

I am taking undergrad genetics and this section only has me very confused. The prof. did not explain it much, I don't have the book only some notes and have an exam tomorrow.

The prof. says: When it comes to drosophila, yellow body color is dominant and it is caused by one gene. She then goes on to write down the following:

e=ebony b=black

e+e+bb X eeb+b+
Black body black body


e+eb+b
She says the offspring is yellow because "it" has a wild type allele for each gene. This proves they are different genes.


What I don't get:

If the offspring has both wild type alleles (ebony and black) how in the world does that give you yellow? How does that prove "they" are different genes? and who is "they"? 😳


I must have gone to the restroom when she went over this or something if you can please help and thank you.

 

[truethat]

Anyone knows? thanks

 

[NehsNairb]

parental: e+e+bb would make one type of gamete e+b
eeb+b+ would make one type of gamete eb+
so
offspring would have to be e+eb+b

e+ means wildtype which is yellow, e means recessive which is ebony
since wildtype gene is dominant, then phenotype would be e+b+ so it offspring would have yellow bodies

i assume "they" refer to genes e and b

i'm guessing it shows that they are different genes because since b+ is dominant and present in the offspring, yet the offspring still has a yellow body, then b must affect something other than body color

this is my decryption of your notes, it would be best to just ask a friend or the prof what she actually meant

p.s. if this is a homework question or some take home quiz, shame on you for asking

 

[kirexhana]

i think e+ and b+ both mean yellow body (or wild type). cuz... yellow body IS wild type. if you have eeb+b+, the body is black because one gene is homozygous recessive. if you have e+e+bb the body is also black beacuse the other gene is homozygous recessive. but if you ahve e+eb+b, then you get yellow (wild type) cuz they're both heterozygous dominant?

it's been a while....

 

[truethat]

Thank yo guys, I think it is making sense, I will go digest it some more

and now I assure you it is not for homework. I have an exam and it is the only section of my notes I could not decipher, thanks 👍

 

[greytmedic]

This is due to Complementation. Which is the production of a wild type phenotype when two haploid gametes bear different recessive mutations come together in the same cell. Since each of the parental flies are mutant phenotype, but together the flies produce offspring of wild type phenotype it means the flies carry different recissive mutations. One gives the e+ and the other gives the b+ so when the two different genes are together you get a heterozygous e+ e/b+ b, with the wild type phenotype. Long story short, look up "Test for complementation" on google.

 

[NehsNairb]

this is making less sense now

if your prof said yellow body color is dominant and is caused by only ONE gene then shouldn't one of the parents be yellow?

if e is that gene, wouldn't e+e+bb be yellow and similarly if b is that gene, wouldn't eeb+b+ be yellow?

 

[crazy_cavalier]

if your prof said yellow body color is dominant and is caused by only ONE gene then shouldn't one of the parents be yellow?

this proves the point that they are separate genes.