The picture below shows a key stage in the process of pre-implantation molecular

Question

The picture below shows a key stage in the process of pre-implantation molecular diagnostic testing of embryos.

What is the NEXT step that will be done in this process?

A) The cell is broken open and a specific DNA sequence or gene inside the cell is copied many times, then this copied DNA is tested. If the test reveals this cell had the normal (desired) version of the gene that impacts the health of the child, the rest of the embryo will have the same gene and these living embryo cells are implanted into the mother to give birth to a healthy baby (a baby with the desired genotype).

B) The cell is the target cell for genetic engineering. This cell is given the desired copy of the gene that impacts the health or specific traits of the baby. The cell is cultured to develop into an embryo and then the embryo cells are implanted into the mother to give birth to a transgenic but healthy baby (a transgenic baby with the desired genotype).

C) The cell will be tested to determine if it has the version of a gene needed for the normal, healthy condition of a certain childhood disease. If it tests positive for the normal or desired gene version, the cell is cultured in a separate petri dish to give rise to a healthy baby.

D) The cell will be tested to determine if it makes a protein needed for the normal, healthy condition of a certain childhood disease. If it tests positive for this protein, the cell is cultured in a separate petri dish to give rise to a healthy baby.

Explanation / Answer

Ans. Correct option: C. The cell is tested for certain suspected alleles (two or more versions / forms of a gene) that might cause genetic abnormalities if present in mutated forms. The cell is generally screened for karyotyping that detects chromosomal abnormalities (abnormal chromosome number of architecture). The cell is also tested for certain mutated alleles using markers. If the cell has normal alleles (and normal karyotype), the embryo is implanted because all the cells of the embryo are genetically identical.

Option A. Incorrect: DNA sequencing of one or more genes is relatively expensive and time consuming procedure. This method is not adopted for testing embryos. Option C is preferred instead that is relatively cost and time effective with equivalent outcomes.

Option B. Incorrect: The cell is NOT target for genetic engineering.

Option D. Incorrect: See Option C. Presence of normal alleles would give normal proteins. There is no need of checking protein produced by the cell.

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