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    i have this question involving drosophila and was hoping someone would be able to shed some light on how i should be doing this...

    Y+=grey body, Y=yellow body
    W+=red eyes, W=white eyes

    Y+,W+ are dominant, linked and situated on the X chromosome

    If a wild type male was crossed with a yellow bodied, white eyed female to produce males with yellow bodies and white eyes and females with grey bodies and red eyes. When these flies were interbred, the offspring consisted of 1002 flies with grey bodies and red eyes, 1004 flies with yellow bodies and white eyes, 15 flies with grey bodies and white eyes and 16 flies with yellow bodies and red eyes.
    Show, using the symbols, Y+,Y,W+,W how the F1 flies were produced and the result of thier inbreeding.


    Anyhelp would be great!
    thanks!
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    (Original post by Dal)
    Y+=grey body, Y=yellow body
    W+=red eyes, W=white eyes

    Y+,W+ are dominant, linked and situated on the X chromosome

    Firstly, linked genes are genes on the chromosome that tend to be inherited together.

    Females are XX but Males are XY - this is important since we are looking at sex-linked genes.

    As we are looking at X-linked genes... females would have two sets of the two genes but males would only have one set of two genes.

    If a wild type male was crossed with a yellow bodied, white eyed female to produce males with yellow bodies and white eyes and females with grey bodies and red eyes.


    Here...

    Female WY WY (white eyes and yellow body)

    Male W+Y+ (red eyes and grey body)

    Offspring:

    Males (XY) have to inherit the X chromosome from the mother because they inherit the Y chromosome from the males.

    Male offspring: WY (white eyes and yellow body)

    Female offspring (XX) on the other hand must inherit the male X chromosome as well as the female.

    Female offspring: W+Y+ WY (red eyes and grey body)

    [B][FONT=Microsoft Sans Serif][I]

    When these flies were interbred, the offspring consisted of 1002 flies with grey bodies and red eyes, 1004 flies with yellow bodies and white eyes, 15 flies with grey bodies and white eyes and 16 flies with yellow bodies and red eyes.
    Show, using the symbols, Y+,Y,W+,W how the F1 flies were produced and the result of thier inbreeding.
    The parents (F1 generation) above then breed together...

    Male: WY (white eyes and yellow body)

    Female: W+Y+ WY (red eyes and grey body)

    This would lead to a 50% chance of white eyes and yellow body and also for red eyes and grey body.

    This is because males (XY) offspring, who if you remember have to inherit the X chromosome from their mother (since they inherit the Y chromosome from the father) can either inherit W+Y+ or WY

    In female (XX) offspring that inherit one X chromosome from the father and one from the mother there is again a 50% percent chance. This is because the colour of the eyes and the body depends on whether they inherit W+Y+ or WY from the mother of father.

    The other flies with grey body and white eyes or yellow bodies and red eyes are formed because you have mixing of chromosomes during chiasmata formation in meiosis, which causes crossing over of chromosomes but notice how few do this - this suggests that the genes for eye and hair colour lie very close of the chromosome.
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    thanks a miilion! but im just wondering.. does this mean that there's no way to actually "show" the recombs forming..using a punnet square or something?
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    (Original post by Dal)
    thanks a miilion! but im just wondering.. does this mean that there's no way to actually "show" the recombs forming..using a punnet square or something?
    Yeah, there is... I can't remember how though... I think you have the sex chromosomes and put the alleles inherited in superscript.
 
 
 
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