X-only nondisjunctional progeny

 

Normal | 4-only | X-only | X and 4 Doubles


The text in parentheses below shows the chromosome content of the oocyte, followed by the phenotype of the progeny.  Remember, only genes for which the fly is mutant are listed, so all other markers are wildtype.



X-linked markers:

yellow (y): The body color is golden brown (wildtype: body is coffee brown)


white (w): The eye color is white (wildtype: eyes are brick red)


Bar (B): A dominant gene that changes the shape of the eye.

    Wildtype (+/+) gives oval eyes

    B/+ Gives kidney bean eyes

    B/B (or B/Y males) have narrow, slit-shaped eyes.


vermillion (v): The eye color is a bright orange-red (wildtype: eyes are brick red)


forked (f): Back bristles are shorter, twisted and split (wildtype: bristles long and straight)



Nullo-X Male (Ø 4) v f B


A shot of the back of the thorax, showing the expression of forked in the bristles.  They are short and twisty.  Note also that these males are wildtype for yellow, matching the body color of the normal females.



A close-up view of the vermillion Bar eye.  The eyes in these males are more orange than the red eyes in the females. Also note the sex comb, slightly out of focus on the right edge of the image.



Diplo-X Female (XX 4) y w B

Females that get both X chromosomes from their mother, so are yellow and white, but are wildtype for the fourth chromosome markers ci, ey and pol.



A closeup of the eye shows the regularly-packed ommatidia in a Bar eye.  This fly is heterozygous for Bar, with yellow body and dark bristles, and so must be FM7 / y w, and arose by Meiosis I nondisjunction (where both homologs go to the same pole).  Females that are y w/y w or FM7/FM7 must have arisen via Meiosis II nondisjunction (where both sister chromatids go to the same pole).