Abstract
An autoradiographic and measurement analysis of the D group chromosomes of a normal woman, a woman heterozygote for an interchange between two non-homologous D chromosomes, and a girl with primary D<sub>l</sub> trisomy has been described. It has been found that D chromosomes with different labelling patterns belong to discrete size classes. The longest pair of D chromosomes (No. 13) are the last to complete DNA synthesis and have a late synthesizing region in the distal part of the long arm. The pair of chromosomes of intermediate length (No. 14) are the second to complete DNA synthesis and show a region of late DNA synthesis in the short arm and proximal part of the long arm. The shortest chromosomes (No. 15) are the first to complete DNA synthesis. The interchange heterozygote has been proved to carry an interchange between two D chromosomes that fit the definitions given here for chromosomes 13 and 14. The chromosome responsible for theDi trisomy syndrome cannot be assigned to a size class, on the basis of the present evidence, and its identification still rests only on the results of autoradiographic analysis.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: 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.
