Please help thank you so much ! A pregnant couple is seeking genetic counselling

Question

Please help thank you so much !

A pregnant couple is seeking genetic counselling after their first born had a genetic disorder. Cytogenetic testing on the parents and the fetus showed the only variation of interest to be located on chromosome 1 and relates to genes A, B, C, D, E, F, and G. Below are the chromosome 1 genotypes of the parents and the fetus ( represents the centromere). Explain how the fetus could get the above genotype? Should the parents be worried about any abnormalities? Is it likely that their future children will have the same genotype? Chromosome Structural Evolution: Predict the order in which the following chromosomal changes may have happened starting from

Explanation / Answer

12.

Mother                        AbC-DEfG, Abc-dEfg           

Father                       ABC-DEFG, abc-defg

Fetus:                          AbfED-CG , Abc-DEFG

The fetus has received the genotype due to inversion and translocation:

For the AbfED-CG: The mother’s chromosome AbC-DEfG has had a inversion around the centromere. Which means that the C-DEf has inverted itself to result into fED-C

For the Abc-DEFG: the chromosome regions have been translocated. The DEFG from the father’s chromosome ABC-DEFG has translocated to the mother’s chromosome Abc-dEfg resulting in a chromosome variant Abc-DEFG.

As the chromosomes have been re-arranged, there is a chance of complications involved.

Since both inversion and translocation are chance events occurring during crossing over, predicting for future children will be difficult and can be done prenatally.

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