Infants and Children in Context. Tara L. Kuther

world where malaria is not a risk. The frequency of the gene is decreasing in areas of the world where malaria is uncommon. For example, only 8% of African Americans are carriers, compared with as much as 30% of Black Africans in some African countries (Maakaron & Taher, 2012). Therefore, the developmental implications of genotypes—and mutations—are context specific, posing benefits in some contexts and risks in others. Recent advances in genetic engineering hold important implications for understanding and treating genetic disorders, as discussed in the Lives in Context feature.

      Lives in Context: Biological Influences

      Genetic Engineering

      We have seen that DNA influences many of our expressed traits. DNA, however, can be changed. Genetic engineering is a technology that permits scientists to change an organism’s DNA. Genetic engineering is commonly used in agriculture and can be applied to modify plants to promote growth, strengthen crop resilience, and improve their nutritional value. In a process known as gene editing, genetic material can be added, removed, or changed at specific places on the genome (National Library of Medicine, 2019). One popular method of gene editing, CRISPR-Cas9 (commonly referred to as CRISPR), has generated a lot of excitement in the scientific community because it is faster, more cost-effective, more accurate, and more efficient than existing genome editing methods (National Library of Medicine, 2019).

      Although gene editing is in its infancy, it is an experimental treatment for some genetic illnesses, including cancer and sickle cell anemia. Often referred to as gene therapy, the CRISPR method is used to manipulate the ill person’s genome. At present, gene therapy is generally available only in research settings such as in experimental cancer treatment, for example (Stein, 2019). However, it holds promise. In recent clinical trials, some patients with sickle cell anemia have shown no signs of the disease after gene editing (Kolata, 2019).

      Ethical concerns arise when gene editing is used to alter the human genome. Research on gene editing is limited to somatic cells, or body cells, because these changes affect only certain tissues and are not passed from generation to generation. Changes to sperm and egg cells, however, can be passed to future generations, posing ethical dilemmas such as the use of gene editing to enhance normal human traits. Because of these ethical issues as well as safety concerns, gene editing is not permitted on sperm and egg cells or embryos.

      In late 2018, Chinese scientist He Jiankui garnered global media attention after using CRISPR to edit the DNA of two embryos. The embryos were implanted and carried to term by their mother. Jiankui’s work was judged as unethical, and he was criticized for using untested, unregulated, and unsafe methods. In addition, the developmental consequences for the infants are unknown and any genetic abnormalities may be passed on to their kin. Jiankui argued that the infants’ genomes were sequenced or mapped after birth, suggesting that only the intended genes were deleted. Nevertheless, the scientific community has condemned Jiankui’s work and Jiankui is facing allegations of scientific misconduct and will also face criminal charges in his home country, China.

      What Do You Think?

      1 What are some of the pros and cons of genetic engineering?

      2 What kinds of conditions should be treated by gene therapy? Are there any conditions that should be off limits to gene therapy?

      Thinking in Context 2.2

      1 Give advice to prospective parents. Explain how genetic and chromosomal disorders are transmitted. What can parents do to reduce the risks?

      2 Recall from Chapter 1 that most developmental scientists agree that nature and nurture interact to influence development. Choose a genetic or chromosomal disorder discussed in this section and explain how it illustrates the interaction of genes and context.

      Reproductive Choices

      The likelihood of genetic disorders often can be predicted before conception. Our growing understanding of genetic inheritance has led many couples to wonder about their own genetic inheritance and what genes they will pass on to their children.

      Genetic Counseling

      Many prospective parents seek genetic counseling to determine the risk that their children will inherit genetic defects and chromosomal abnormalities (Ioannides, 2017; Uhlmann, Schuette, & Yashar, 2009). Candidates for genetic counseling include those whose relatives have a genetic condition, couples who have had difficulties bearing children, women over the age of 35, and couples from the same ethnic group. Genetic testing can also determine whether a couple’s difficulty conceiving or recurrent miscarriage is influenced by sperm chromosomal abnormalities in the male (Kohn, Kohn, Darilek, Ramasamy, & Lipshultz, 2016).

      The genetic counselor interviews the couple to construct a family history of heritable disorders for both prospective parents. This service is particularly valuable when one or both prospective parents have relatives with inborn disorders. If a disorder is common in either parent’s family or it appears that they are likely to carry a genetic disorder, genetic screening blood tests may be carried out on both parents to detect the presence of dominant and recessive genes and chromosomal abnormalities associated with various disorders. The tests determine whether each parent is a carrier for recessive disorders and estimate the likelihood that a child may be affected by a genetic disorder. The genetic counselor interprets the results and helps the parents understand genetic concepts by tailoring the explanation to match the parents’ knowledge (Nance, 2017).

      Once prospective parents learn about the risk of conceiving a child with a disorder, they can determine how to proceed—whether it is to conceive a child naturally or through the use of in vitro fertilization—after screening gametes for the disorders of concern. Given advances in our knowledge of genetic disorders and the ability to screen for them, some argue that genetic counseling should be available to all prospective parents (Minkoff & Berkowitz, 2014). Others argue that abnormalities are rare and so few would be discovered that universal screening is of little utility (Larion, Warsof, Maher, Peleg, & Abuhamad, 2016). Whether to seek genetic counseling is a personal decision for prospective parents based on their history, view of their risks, and their values. Adults who carry significant risks of conceiving a child with a genetic disorder sometimes consider alternative methods of reproduction.

      Assisted Reproductive Technology

      Couples turn to assisted reproductive technology for a variety of reasons. As noted, some couples at risk for bearing children with genetic or chromosomal abnormalities seek alternative methods of conception. About 15% of couples in the United States experience infertility, the inability to conceive (Thoma et al., 2013). About 35% of the time, factors within the male are identified as contributors to infertility (Centers for Disease Control and Prevention, 2017c). In addition, single men and women, as well as gay and lesbian couples, often opt to conceive with the use of reproductive technology. However, there are racial, ethnic, and socioeconomic disparities in the use of assisted reproductive technologies. Women and couples who are White, college educated, and of high socioeconomic status (SES) are more likely to use infertility services than African American and Hispanic couples (Janitz, Peck, & Craig, 2016). Race and ethnicity are often linked with socioeconomic status and disparities in health care in the United States. Socioeconomic factors play a large role in access to infertility treatment and assisted reproductive technology (Dieke, Zhang, Kissin, Barfield, & Boulet, 2017).

      One assisted reproduction technique is artificial insemination, the injection of sperm into a woman. The male partner’s sperm may be used or, if the male experiences reproductive difficulties, a donor’s sperm may be used. Artificial insemination through a donor also enables women without male partners, whether single or lesbian, to conceive. The most expensive assisted reproductive technology, in vitro fertilization, tends to average over $12,000 per trial, not including medication, and often requires multiple cycles, posing a financial burden too great for low SES women and couples