Does an earthworm have an open or closed circulatory system explain

Apair of fruit flies reproduces and has 1,000 offspring. all 1,000 of the offspring have the alleles gg. what is the most likely combination of alleles for each parent

To be or not to be that is da question

During crossing-over, a. genetic material is exchanged between nonsister chromatids, resulting in new combinations of alleles. b. nonsister chromatids from each homologous chromosome of a tetrad are exchanged, resulting in new combinations of alleles. c. one homologous chromosome of a tetrad is exchanged with another tetrad, resulting in new combinations of alleles. d. sister chromatids from each homologous chromosome of a tetrad are exchanged, resulting in new combinations of alleles. e. genetic material is exchanged between sister chromatids, resulting in new combinations of alleles.