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relationship to other organisms

relationship to other organisms - York the smallest visible...

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relationship to other organisms If a paint is made from a human chromosome it can be applied to the chromosomes of other species. This image is of marmoset chromosomes to which a human chromosome 8 paint has been applied. This shows homology with the short arm of marmoset chromosome 13, and the whole of marmoset chromosome 16. Sherlock et al., (1996) Homologies between human and marmoset (callithrix jacchus) chromosomes revealed by comparative chromosome painting. Genomics 33: 214-9 numerical abnormalities One of the commonest mutations is a change in the chromosome number but it is also one of the most damaging occurences. Very few mutations which cause visible changes in the autosomes are compatible with life. Conor and Ferguson-Smith make the analogy that if the length of the human haploid genome was drawn stretching from London to New
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Unformatted text preview: York, the smallest visible deletion (about 4Mb) would represent about an 8 km gap and that on this scale, the average gene would be about 30 m long. So even the smallest gap will usually contain many genes. About 20% of conceptions have some sort of chromosomal disorder but because of the lethal effects of such disorders, the number actually born is only about 0.6%. chromosome abnormalities in early spontaneous abortions Defect frequency triploidy 10% tetraploidy 5% trisomy 30% Turner syndrome (45 X) 10% other 5% Total 60% A wonderful resource for the next section is the University of Tokyo Medical School where someone has laboured long and hard to make all sorts of moving images to explain chromosome rearrangements...
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