Abstract
In unfertilized sea urchin eggs treated with NH(4)OH-sea water, the chromosomes condense after a first round of DNA synthesis and go through a chromosome cycle. The chromosomes split visibly, but sister chromosomes are not further separated. They regress into an interphase nucleus. These cycles repeat, producing eggs with large numbers of chromosomes. No mitotic apparatus is seen and the eggs do not divide. There is some microscopic evidence of limited chromosome movement, interpreted as centrifugal movement of the condensed chromosomes before they split and a centripetal movement as the split chromosomes decondense to reconstitute the nucleus. The eggs so treated with NH(4)OH are considered to be unfertilized eggs and can be fertilized later. Such later fertilization permits the introduction of paternal nuclei after the maternal nuclei have progressed some way toward the above-described chromosome condensation. The paternal chromosomes condense prematurely at the time when the maternal chromosomes condense. At the same time, premature with respect to the time of fertilization, mitotic apparatus form.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.