The most common reason a physician might recommend that ...

Question

The most common reason a physician might recommend that a woman have maternal serum screening and a karyotype analysis is concern that her fetus may have Down syndrome. Go to the OMIM website at www.ncbi.nlm.nih.gov/omim and look up Down syndrome (OMIM 190685).

Look at the 'Mapping' and 'Molecular Genetics' sections and describe what is meant by the Down syndrome critical region (DSCR).

Accepted Answer

Hello, everyone. Let's look at our next question. It says the Down Syndrome critical region, DS C R which contains genes responsible for many features of Down Syndrome is located on which of the following chromosomes. And our answer choices are a chromosome 13 B, chromosome 18 C, chromosome 21 or D chromosome 22. Well, as we might recall from our content, video Down Syndrome is caused by Trisomy 21, meaning that there are three copies present of chromosome 21. So we're talking about where would we expect the genes to be that are responsible for many of the features of Down Syndrome? It would make sense that those genes are located on chromosome 21 since having that extra copy is what causes the syndrome. And indeed this is correct and that's choice. C and these, it's been determined that genes on a small region of chromosome 21 are responsible for the mental and developmental delays and heart abnormalities that are the principal features or symptoms of Down Syndrome. And it's that particular region because those genes in that short little part are responsible for those features. That's been named the Down Syndrome Critical region. And again, that's located on which the following chromosomes choice C chromosome 21. See you in the next video.

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