USMLE Forum Archives - USMLE Step 1 - genetics
genetics
bingousmle - 12-30-08 13:10
A child with cleft palate, a heart defect, and extra fifth fingers is found to have 46 chromosomes with extra material on one homologue of the chromosome 5 pair. This chromosomal abnormality is best described by which of the following terms?
A. Polyploidy
B. Balanced rearrangement
C. Ring formation
D. Mosaicism
E. Unbalanced rearrangement
bingousmle - 12-30-08 13:10
A child with cleft palate, a heart defect, and extra fifth fingers is found to have 46 chromosomes with extra material on one homologue of the chromosome 5 pair. This chromosomal abnormality is best described by which of the following terms?
A. Polyploidy
B. Balanced rearrangement
C. Ring formation
D. Mosaicism
E. Unbalanced rearrangement
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#2
Re: genetics
bingousmle - 01-01-09 05:00 E....there is no change in number of the autosomes (nonsex chromosomes) or sex chromosomes (X and Y chromosomes). The question implies that all cells karyotyped from the Chromosomal abnormalities may involve changes in number (i.e., polyploidy and aneuploidy) or changes in structure (i.e., rearrangements such as translocations, rings, and inversions). Extra material (i.e., extra chromatin) seen on chromosome 5 implies recombination of chromosome 5 DNA with that of another chromosome to produce a rearranged chromosome. Since this rearranged chromosome 5 takes the place of a normal chromosome patient (usually 11 to 25 cells) have the same chromosomal constitution, ruling out mosaicism. The patient's clinical findings are similar to those occurring in trisomy 13, suggesting that the extra material on chromosome 5 is derived from chromosome 13, producing an unbalanced karyotype called dup(13) or partial trisomy 13.
#3
Re: genetics conym5 - 11-16-09 08:57 The question implies that all cells karyotyped from the
patient (usually 11 to 25 cells) have the same chromosomal constitution,
ruling out mosaicism. The patient’s clinical findings are similar to those
occurring in trisomy 13, suggesting that the extra material on chromosome
5 is derived from chromosome 13, producing an unbalanced karyotype
called dup(13) or partial trisomy 13.
#4
Re: genetics babbu5508 - 06-24-10 13:26 E. Unbalanced rearrangement...because one of the chromosomes has extra material on themselves while the others are normal.
#5
Re: genetics bingousmle - 06-30-10 20:34 
posted by conym5 on 11-16-09 08:57
The question implies that all cells karyotyped from the
patient (usually 11 to 25 cells) have the same chromosomal constitution,
ruling out mosaicism. The patient’s clinical findings are similar to those
occurring in trisomy 13, suggesting that the extra material on chromosome
5 is derived from chromosome 13, producing an unbalanced karyotype
called dup(13) or partial trisomy 13.
The question implies that all cells karyotyped from the
patient (usually 11 to 25 cells) have the same chromosomal constitution,
ruling out mosaicism. The patient’s clinical findings are similar to those
occurring in trisomy 13, suggesting that the extra material on chromosome
5 is derived from chromosome 13, producing an unbalanced karyotype
called dup(13) or partial trisomy 13.
yeah you are right as Extra material (i.e., extra chromatin) seen on chromosome 5 implies recombination of chromosome 5 DNA with that of another chromosome to produce a rearranged chromosome.
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