Document Detail

The chromosome complement of human gametes.
MedLine Citation:
PMID:  1437215     Owner:  NLM     Status:  MEDLINE    
The comparisons of observed and predicted rates of chromosomally abnormal gametes for two major classes of abnormality and for three specific trisomies are summarized in Table 2.10. As can be seen there is not very good agreement between the two sets of data. For sperm the observed abnormality rates are, with the exception of polyploidy, all in excess of those predicted. For structural abnormalities the excess is absurd and suggests that most structural abnormalities seen in sperm chromosomes may be preparation artefacts. On the other hand, it could be argued that the excess of hyperhaploidy among sperm is real and represents those trisomic conceptuses lost in the early stages of pregnancy. However, both chromosome 21 and the sex chromosomes are represented more often than any other chromosomes. Recent observations among all clinically recognized pregnancies do not suggest an excess of trisomy 21 conceptions arising from non-disjunction in spermatogenesis. As can be seen from Table 2.10, the observed frequencies of trisomy 21 is 10 times greater than that predicted, a difference that seems too great to be accounted for by early pregnancy wastage. While the X chromosome does appear to undergo non-disjunction much more frequently than the autosomes during spermatogenesis, the increase is restricted to non-disjunction of the XY bivalent at the first male meiotic division. In this class the observed and predicted frequencies are rather similar and it is even possible that the observed excess in sperm is accounted for by early post-zygotic loss. However, with the exception of the 24, XY class, the distribution of individual chromosomes among the hyperhaploid sperm bears little relation to that predicted. The most likely explanation for this is that banding of sperm chromosomes is of such poor quality that there are many errors in the identification of individual chromosomes. Most authors use some form of Q banding and this technique should give unequivocal identification of the highly-fluorescent Y chromosome even when other chromosomes are not clearly distinguishable. An increased accuracy of Y-chromosome identification may account for the relative concordance between observed and predicted rates of 24, XY sperm. By the same argument, 24, YY sperm might be expected to be accurately enumerated.(ABSTRACT TRUNCATED AT 400 WORDS)
P A Jacobs
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Publication Detail:
Type:  Journal Article; Review    
Journal Detail:
Title:  Oxford reviews of reproductive biology     Volume:  14     ISSN:  0260-0854     ISO Abbreviation:  Oxf Rev Reprod Biol     Publication Date:  1992  
Date Detail:
Created Date:  1992-12-02     Completed Date:  1992-12-02     Revised Date:  2005-11-16    
Medline Journal Info:
Nlm Unique ID:  8005460     Medline TA:  Oxf Rev Reprod Biol     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  47-72     Citation Subset:  IM    
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MeSH Terms
Abortion, Spontaneous / genetics
Chromosome Aberrations*
Fetal Death / genetics
Oocytes / ultrastructure*
Spermatozoa / ultrastructure*

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