Polytene chromosomes normal.
Increases the frequency of X chromosome non-disjunctions in noda mutants.
Homozygous larval brain ganglia have a reduced ability to synthesise DNA from an undamaged template compared to wild-type.
The mei-S2821 mutation causes mitotic chromosome instability.
The reduced levels of reciprocal exchange which are characteristic of mei-S2821 females allow for high frequencies of meiotic loss and nondisjunction.
Nondisjunction in mei-S2821 females occurs at the first meiotic division and only nonexchange chromosomes nondisjoin.
Non-disjunction of all the chromosomes is increased compared to wild-type in females. Nondisjunction occurs at the first meiotic division and nondisjunction of the different chromosome pairs is highly correlated. Crossing over is reduced to about 1/2 the control value, with the reduction being most pronounced distally. Segregation of the sex and 4th chromosomes is normal in mutant males.
Females homozygous for mei-S2821 exhibit reduced levels of meiotic exchange. The residual exchanges are distributed such that the probability of euchromatic exchange becomes more proportional to unit length (FBrf0025068; FBrf0028329). This relaxation of the normal constraints on the distribution of euchromatic exchange is clearly demonstrated by the ability of mei-S2821 females to allow exchange on the normally achiasmate fourth chromosome (Sandler and Szauter, 1978).
Isolated from: winery, about 15 kilometres northeast of Rome, Italy, October 1965.
