What can't be determined with a karyotype

[horsebox]

I came across this question

Which of the following cannot be detected using karyotyping?

a)sex of a fetus
b)trisomy 21
c)chromosomal translocations
d)aneuploidy
e)nucleotide substitutions

I know b and d can be seen but you couldn't really see translocations and nucleotide substitutions unless you compared the karyotype to a human karyotype without these mutations could you? As for the sex of a fetus I don't get it. If the karyotype is done on chromosomes from the fetus itself obviously you can tell but otherwise I don't know what this question is about.

 

[Hercules Rockefeller]

I know b and d can be seen...

Correct.

...but you couldn't really see translocations...

Yes, you can. An experienced cytologist/cytogeneticist can spot abnormal chromosomes that contain translocations.

...and nucleotide substitutions...

At the chromosomal level you cannot determine single nucleotide alterations to DNA sequences. Fluorescence in situ hybridisation (FISH) might be able to determine large scale insertions or deletions in the chromosome spread, but does not have the resolution to determine single nucleotide differences. This would require DNA sequencing or other SNP analysis techniques (eg. DNA melt analysis) to determine single nucleotide changes. So, the answer to the question is (e).

As for the sex of a fetus I don't get it. If the karyotype is done on chromosomes from the fetus itself obviously you can tell but otherwise I don't know what this question is about.

Amniocentesis can be used to isolate foetal cells and enables a foetal karyotype analysis. This allows direct visualisation of the sex chromosomes and determination of the sex of the foetus or determination of trisomy.

 

[horsebox]

Thanks a lot.