Suppose you read in the newspaper that a genetic engineering laboaratoty has dev

Question

Suppose you read in the newspaper that a genetic engineering laboaratoty has developed a procedure for fusing 2 gametes from the same person(2 eggs or 2 sperm) to form a zygote. The article mentions that an early step in the procedure prevents crossing over from occuring during the formation of the gametes in the donor's body. The researchers are in the process of determining the genetic makeup of one of their new zygotes. Which of the following predictions do you think they would make? Justify your choice , and explain why you rejected the other choices.

a) The zygote would have 46 chromosomes , all of which came from the gamete donor (its one parent) so the zygote would be genetically identical to the gamete donor.

b) The zygote COULD be genetically identical to the gamete donor, but it is much more likely that it would have an unpreidctable muxture of chromosomes from the gamete donor's parents

c) The zygote wouild not be genetically identical to the gamete donor , but it would be genetically identical to one of the donor's parents

d) The zygote would not be genetically identical to the gamete donor , but it would be genetically identical to one of the donor's grandparents.

Explanation / Answer

a) The zygote would indeed have 46 chromosomes,since the fusion of two haploid (n) cells in a human produced a 46 chromosome cell. However, the zygote is not necessarily genetically identical to the donor since, during meiosis which forms the gametes, the choice of which of the 2 homologous chromosomes ends up in the resultant gamete is random. As a result there will be a random combination of chromosomes in each gamete. b) This is the correct answer. The zygote will only be genetically identical if the two zygotes fused together have complimentary homologous chromosomes. It is most likely that this will not be the case, and instead there will be a random mix in each gamete of the donor's chromosomes, which originate from the donor's parents, and these random mixes will not, when put together, form the donor's genetic makeup. c) The zygote cannot be genetically to one of the donor's parents, as they only passed half of their DNA each to the donor. d) For the same reason as in c, but with one additional generation, there is no way for the entirety of the genetic makeup of the grandparents to reach the donor, let alone the zygote formed.

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