Dr. Vijay has identified two of the most plausible hypotheses for Lillian’s chim

Question

Dr. Vijay has identified two of the most plausible hypotheses for Lillian’s chimerism: a) that Lillian is the result of the fusion two independently fertilized embryos b) that Lillian is the result of the fusion of an ovum fertilized by one sperm and a polar body fertilized by a second sperm. Each hypothesis depends upon a series of unusual events in the reproductive cycle in Lillian’s mother. Explain the series of events that would have to have occurred in each case, noting those that are abnormal.

Explanation / Answer

Case A)

The oocytes of Lillian mother were harvested. These were fertilized with sperms taken from anonymous donors. Separate zygotes were formed and maintained in separate dishes. At the four-cell stage, two embryos were transferred to Lillian’s mother. After 5 weeks ultrasonography was done. A single fetus was seen. This means that fetus is formed by the amalgamation of two separate embryos. It will possess two cell lines.

Such a case is called as ‘complete chimerism’.

Case B)

The polar bodies are the haploid cell released from the ovum during meiosis. These do not have the ability of fertilization.

Note that oocytes are harvested by giving chemical treatment to the female gonads. In this condition, the polar body can gain the ability of fertilization.

The harvested oocyte was given sperm treatment for fertilization in a dish. Two zygotes were formed, one by the fusion of ova and sperm the other by fusion of any of the polar bodies with another sperm.

When these embryos are transferred to Lillian’s mother’s uterus a single fetus was formed; resulting into chimerism.

Related Questions

Navigate

• Browse (All)
• Browse D
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.