BACKCROSS HELP
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BACKCROSS HELP
hi there everyone,
i'm new so if ths goes wrong sorry, at the moment i am studying backcrossing and genes ect. i know what backcrossing is and the results but please please please can some one tell me how to set a backcross up for animals/fruite flies.
thank you for reading hope u can help.
i'm new so if ths goes wrong sorry, at the moment i am studying backcrossing and genes ect. i know what backcrossing is and the results but please please please can some one tell me how to set a backcross up for animals/fruite flies.
thank you for reading hope u can help.

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- Location: Michigan
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- Location: Michigan
Here's a example:
Say that you cross a Homozyogous Dominant parent for black fur(noted by BB) and a Homozygous Recessive parent for white fur(noted by bb)
The cross between them would produce a genotype of Bb, or Heterozygous. The Phenotype (what it looks like) would be black fur because black fur is dominant to white fur.
The Punnet Square looks like this
B B
b Bb Bb
b Bb Bb
Say that you cross a Homozyogous Dominant parent for black fur(noted by BB) and a Homozygous Recessive parent for white fur(noted by bb)
The cross between them would produce a genotype of Bb, or Heterozygous. The Phenotype (what it looks like) would be black fur because black fur is dominant to white fur.
The Punnet Square looks like this
B B
b Bb Bb
b Bb Bb
No News is Good News
Alex
Alex
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- Location: Michigan
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- Location: Michigan
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To backcross with fruit flies you would use the same method>>>>>>>>>
Say that red eye color is dominant
RR=Homozygous Dominant=Red eye color
Rr=Heterozygous=Red eye color
rr=Homozygous recessive=Green eye color
That is only if it is complete dominance.
If you need help with incomplete dominance or co-dominance or two-trait cross just ask!!!
Say that red eye color is dominant
RR=Homozygous Dominant=Red eye color
Rr=Heterozygous=Red eye color
rr=Homozygous recessive=Green eye color
That is only if it is complete dominance.
If you need help with incomplete dominance or co-dominance or two-trait cross just ask!!!
No News is Good News
Alex
Alex
hi again, thanks again. the question i'm lookin at solving as a female fruit fly with red eyes and a grey body, the male as brown eyes and a yellow body. and all the f1 offspring have taken after the mother all say 47 are red eyed and have grey bodys. and this is what i need to set up a back cross for. i know the ressesive is the male but thats about it.
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The only way somthing like that where all offspring show dominant traits is if the mother was completely dominant meaning her genotypes for RR for red eyes and GG for grey bodies. Then the male would have to be homozygous recessive for both of the traits.
rr for brown eyes and gg for yellow body. Finnally the offspring would all have heterozygous. Rr for red eyes and Gg for grey bodies.
Anything else?
rr for brown eyes and gg for yellow body. Finnally the offspring would all have heterozygous. Rr for red eyes and Gg for grey bodies.
Anything else?

No News is Good News
Alex
Alex
yay i'm getting it, i cannt thank you enough this was one thing i just couldnt get my head around, theres just one thing i STILL dont get, and thats if your setting up a back cross to breed all f1 offspring females with the farther(i'm i right) then how can you determin which are male which are femal and make sure they dont breed with there bros and sisters?
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That question is a hard one to answer. Back Crosses take an offspring and cross with a parent. So theres no way that the offspring could breed with it's brother or sister in a backcross problem. A female offspring can only cross wtih the male parent. And a male offspring can only cross with a female parent. You must take all the possible genotypes of the offspring and cross them with the parent. Since you cannot determine what will be female in the F1 generation you must except that all of them would be female. Simply cross the male parent with every type of offspring.
Note that recessive traits are implied with backcrosses
Note that recessive traits are implied with backcrosses
No News is Good News
Alex
Alex
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