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a Some Genetic Diseases Detected with Preimplantation Genetic Diagnosis achondroplasia (dwarfism)

adenosine deaminase deficiency (immune deficiency)

alpha-1-antitrypsin deficiency (emphysema)

Alzheimer disease susceptibility beta thalassemia (anemia)

cancer syndromes (p53 gene)

cystic fibrosis epidermolysis bullosa (skin disorder) Fanconi anemia hemophilia A and B (clotting disorder) Huntington disease inborn errors of metabolism Gaucher disease ornithine transcarbamylase deficiency phenylketonuria Tay Sachs disease muscular dystrophies neurofibromatosis retinoblastoma retinitis pigmentosa sickle cell disease spinal muscular atrophy junct to IVF, because it ensures that only the healthiest embryos are implanted. This avoids multiple births and having to remove some embryos later in development so that the ones that are left have enough room to develop.

As with any technology, particularly one that affects conception of offspring, preimplantation genetic diagnosis has raised ethical concerns. At first in the 1990s, many people objected to the idea of intentionally conceiving a child to provide tissue to help an older sibling, but these outcries abated somewhat as the families involved demonstrated that they indeed loved their younger children. A fear now is that human genome information will be used in conjunction with the technology to select children with less medically compelling characteristics — such as gender, inherited susceptibilities, intelligence, personality traits or appearance. ■

Blastocyst —

Blastocyst —

Trophoblast

-Uterine wall

Trophoblast

Lumen

--Inner cell mass

-Uterine wall

Invading trophoblast

Figure 23.5

(a) About the sixth day of development, the blastocyst contacts the uterine wall and (b) begins to implant. (c) Light micrograph of a blastocyst from a monkey in contact with the endometrium of the uterine wall (150x).

Figure 23.5

(a) About the sixth day of development, the blastocyst contacts the uterine wall and (b) begins to implant. (c) Light micrograph of a blastocyst from a monkey in contact with the endometrium of the uterine wall (150x).

Distinguish between growth and development.

What changes occur during cleavage?

How does a blastocyst attach to the endometrium?

In what ways does the endometrium respond to the activities of the blastocyst?

Endometrium —

Lumen

Endometrium —

Light micrograph of a human cleavage embryo (arrow) implanting in the endometrium (18x).

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100 Pregnancy Tips

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