CHANGING THE SEX CHROMOSOMES IN C. ELEGANS

I. Wild-type

II. Using tra-1 mutations

tra-1(o) mutations [(o) signifies a loss of gene function] are recessive and turn the animals (whether XO or XX) into phenotypic males.

tra-1(d) mutations are dominant and turn XO or XX animals into females.

The tra-1 gene is on the third chromosome.

The cross tra-1(d)/tra-1(o)female X tra-1(o)/tra-1(o)male will produce the same male and female progeny.

If we rename the tra-1(d)-containing chromosome W and the tra-1(o)-containing chromosome Z, we see that we have a WZ/ZZ system.

III. Using an IV:X translocation

If an X chromosome is joined to a IV chromosome (X-ray can cause this), we get a translocation chromosome (IV:X).

Animals with one normal IV, no normal X, and one IV:X translocation are males.

Animals with two IV:X translocations are hermaphrodites.

If we rename the IV chromosome Y and the IV:X translocation X, we see that we have produced an XX/XY system.