Final answer:
In preimplantation genetic diagnosis (PGD), genetic screening of embryos (1), in vitro fertilization (IVF) (2), and embryo transfer (3) are all steps involved in the process. Preimplantation genetic diagnosis is a technique that aims to prevent genetic diseases by testing embryos outside the womb before implantation.
Step-by-step explanation:
Steps in preimplantation genetic diagnosis (PGD) certainly include genetic screening of embryos and in vitro fertilization (IVF). These are integral parts of PGD, where embryos are first created outside the mother's body, typically in a petri dish through IVF, and then screened for genetic abnormalities before being implanted into the uterus. Among the options provided, 1), 2) and 3) are directly involved in PGD process. Option 4), prenatal testing, is not considered a part of PGD as it is conducted after implantation of the embryo and during pregnancy.
PGD is a cutting-edge procedure pursued by prospective parents to prevent the inheritance of genetic diseases, such as sickle cell disease, muscular dystrophy, and hemophilia. During IVF, eggs are collected from the ovaries, fertilized, and then embryos grow to either the eight-cell stage or the more robust blastocyst stage before implantation. Genetic screening during PGD occurs at these initial growth stages, where embryos are examined for specific genetic markers indicating the presence of disease-causing alleles. Only embryos without these alleles are selected for transfer into the uterus using a plastic catheter. The depth of analysis in PGD can range from single gene disorders, chromosomal abnormalities to sex determination, but it does not include diagnosis for sexually transmitted diseases. As such, PGD provides an option for parents concerned with genetic disorders in their family history to have children without those conditions, despite PGD's cost-related limitations.