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Full file at http://testbank360.eu/test-bank-essentials-of-human-development-1st-edition-kail Chapter 2 Biological Foundations: Heredity, Prenatal Development, and Birth LEARNING OBJECTIVES In the Beginning: 23 Pairs of Chromosomes What are chromosomes and genes? How do they carry hereditary information? How is children’s heredity influenced by their environments? From Conception to Birth What happens to a fertilized egg in the first two weeks after conception? When do body structures and internal organs emerge in prenatal development? When do body systems begin to function well enough to support life? Influences on Prenatal Development How is prenatal development influenced by a pregnant woman’s age, her nutrition, and the stress she experiences? How do diseases, drugs, and environmental hazards affect prenatal development? What general principles affect the ways that prenatal development can be harmed? How can prenatal development be monitored? Can abnormal prenatal development be corrected? Labor and Delivery What are the different phases of labor and delivery? What are “natural” ways of coping with the pain of childbirth? What adjustments do parents face after a baby’s birth? What are some complications that can occur during birth? What contributes to infant mortality in developed and least developed countries? CHAPTER OUTLINE I. In the Beginning: 23 Pairs of Chromosomes A. Mechanisms of Heredity 1. Human cells have 23 pairs of chromosomes, 22 pairs of autosomes, plus the sex chromosomes (XY for a boy; XX for a girl). 2. Each chromosome consists of one molecule of DNA (deoxyribonucleic acid). 3. Each group of compounds that provides a specific set of biochemical instructions is a gene. 4. Genotype refers to the complete set of genes a person inherits, and phenotype refers to the expressed genes that result from the interaction of the genotype and the environment. 5. Different forms of the same gene are called alleles. 15 Chapter 2 a) When the alleles in a pair of chromosomes are the same, they are called homozygous; when they are different, they are called heterozygous. b) When a person is heterozygous, the instructions of the dominant allele are followed, whereas those of the recessive allele are ignored. 6. A person must inherit two recessive alleles for sickle-shaped cells in order to develop sickle-cell disease. 7. Down syndrome occurs when individuals have an extra 21st chromosome. 8. Abnormal sex chromosomes can also disrupt development. B. Heredity, Environment, and Development 1. When phenotypes reflect the combined activity of many separate genes, the pattern is known as polygenic inheritance. 2. Twins and adopted children provide important information about the role of heredity. Identical twins are called monozygotic twins because they come from a single fertilized egg that splits in two. Fraternal, or dizygotic, twins come from two separate eggs fertilized by two separate sperm. 3. The path from genes to behavior is mostly unknown, but there are some general known properties: a) Heredity and environment interact dynamically throughout development. A good example is the disease PKU. b) Genes can influence the kind of environment to which a person is exposed. In other words, nature can help determine the kind of “nurturing” that a child receives. The process of deliberately seeking environments that fit one’s heredity is called nichepicking. c) Environmental influences typically make children within a family different. Nonshared environmental influences, the forces within a family that make children different from one another, are important. II. From Conception to Birth A. Overview of prenatal development 1. Prenatal development refers to the many changes that transform the fertilized egg into a newborn. The process takes an average of 38 weeks. B. The Period of the Zygote (Weeks 1-2) 1. Zygote is the technical term for the fertilized egg. 2. This period ends when the zygote becomes implanted in the wall of the uterus. 3. The germ disc, a small cluster of cells near the center of the zygote, will eventually develop into a baby. 4. The layers of cells closest to the uterus will become the placenta, a structure through which nutrients and wastes are exchanged between the mother and the developing organism. 5. Implantation occurs when the zygote burrows into the uterine wall and connects with the woman’s blood vessels. C. The Period of the Embryo (Weeks 3-8) 1. Once the zygote is embedded in the uterine wall, it is called an embryo. 2. During this period, body structures and internal organs develop rapidly. 3. The embryo rests in a sac called the amnion, which is filled with the amniotic fluid that cushions the embryo and maintains temperature. 4. The umbilical cord houses blood vessels that join the embryo to the placenta. D. The Period of the Fetus (Weeks 9-38) 1. During this period, the fetus becomes much larger, and its bodily systems begin to work. 16 Full file at http://testbank360.eu/test-bank-essentials-of-human-development-1st-edition-kail 2. By 22 to 28 weeks, most systems function well enough that a fetus born at this time has a chance to survive, which is called the age of viability. III. Influences on Prenatal Development A. Factors affecting prenatal development include a pregnant woman’s age, her nutrition, her stress level, disease, drugs, and environmental hazards. B. General Risk Factors 1. Nutrition a) The mother is the developing child’s sole source of nutrition, so a pregnant woman should increase both her calories and her intake of proteins, vitamins, and minerals. 2. Stress a) Women who report greater anxiety during pregnancy often give birth early or have babies who weigh less than average. Their children are less able to pay attention as infants and more prone to behavioral problems as preschoolers. b) Increased stress in a pregnant woman can reduce the flow of oxygen to the fetus, weaken a pregnant woman’s immune system, and make her more likely to smoke or drink alcohol and less likely to rest, exercise, and eat properly. 3. Mother’s Age a) Compared to women in their 20s, teenage girls are more likely to have problems during pregnancy, labor, and delivery. Their children tend to do less well in school and are more likely to have behavioral problems. b) Women in their 30s are less fertile then they were in their 20s and are more prone to miscarriage. Women in their 40s are more liable to give birth to a baby with Down syndrome. C. Teratogens: Drugs, Diseases, and Environmental Hazards 1. A teratogen is an agent that causes abnormal prenatal development. 2. Drugs a) Teratogens include alcohol, aspirin, and nicotine. b) The use of alcohol carries serious risk. Pregnant women who regularly consume quantities of alcohol often give birth to babies with fetal alcohol spectrum disorder (FASD). 3. Diseases a) AIDS, genital herpes, cytomegalovirus, rubella, and syphilis are teratogens. 4. Environmental hazards a) Environmental teratogens are dangerous because people are unaware of their presence in the environment. D. How Teratogens Influence Prenatal Development 1. The impact of teratogens depends on the genotype of the organism, changes over the course of prenatal development, affects different aspects of prenatal development depending upon the specific teratogen, depends on the dose, and may not be evident at birth but may appear later in life. E. The Real World of Prenatal Risks 1. Many infants are exposed to general risks and multiple teratogens. It is often challenging for researchers to determine the harm associated with individual teratogens. F. Prenatal Diagnosis and Treatment 1. In ultrasound, sound waves are used to generate a picture of the fetus. 2. In amniocentesis, a needle is inserted through the mother’s abdomen to obtain a sample of the amniotic fluid that surrounds the fetus. 3. In chorionic villus sampling, a sample of tissue is obtained from part of the placenta. 4. Fetal medicine is a new field concerned with treating prenatal problems before birth. 17 Chapter 2 IV. Labor and Delivery A. Stages of Labor 1. Labor is the most intense, prolonged physical effort that humans experience. 2. Labor consists of three stages: an initial phase in which the cervix enlarges and contractions begin; the crowning phase when the baby passes through the cervix and enters the vagina; and the phase in which the mother expels the placenta (also called the afterbirth). B. Approaches to Childbirth 1. The “natural” or prepared approach to childbirth believes in going to classes to learn about pregnancy and childbirth; using natural methods to deal with pain rather than medication; and involving a supportive “coach.” C. Adjusting to Parenthood 1. A woman experiences many physical changes after birth. 2. Roughly half of new mothers experience the “baby blues.” 3. About 10 to 15 percent of new mothers develop postpartum depression, which is a serious condition. D. Birth Complications 1. Several birth complications can surface during labor and delivery, which can have longterm effects on the child. 2. If the flow of blood in the umbilical cord is disrupted, the infant does not receive adequate oxygen, a condition known as hypoxia. 3. Babies born before the 36th week are called preterm or premature. 4. Newborns who weigh 2,500 grams or less are said to have low birth weight; those who are less than 1,500 grams are said to have very low birth weight; and those who weigh less than 1,000 grams are said to have extremely low birth weight. Babies in the latter two categories do not fare well. 5. Long-term positive outcomes for at-risk infants depend critically on providing a supportive and stimulating home environment. E. Infant Mortality 1. The infant mortality rate is defined as the percentage of infants who die before their first birthday. 2. Among developed nations, the United States ranks near the bottom because the U.S. has more babies with low birth weight than virtually all other developed countries. LECTURE AND DISCUSSION TOPICS 1. How much do genes matter? Students often wonder the extent to which genes affect our behaviors and our features. Steven Pinker offers an engaging discussion on this topic in his article “Are Your Genes to Blame? For Your Good Looks? Sure. For Your Shyness or Your Temper? Not Entirely.” You can use this article to create lecture points about behavioral genetics and the limitations of genetics in explaining human characteristics. Pinker also makes an argument about genes and legal responsibility, as well as shares advice for personal improvement. Pinker, S. (2003). Are your genes to blame? For your good looks? Sure. For your shyness or your temper? Not entirely. Time, 161, 98. 18 Full file at http://testbank360.eu/test-bank-essentials-of-human-development-1st-edition-kail 2. Preimplantation genetic diagnosis. The textbook discusses various prenatal diagnostic techniques well, but you can enrich this discussion by covering genetic testing that can occur before implantation. While only an option for couples conceiving via reproductive technologies, preimplantation genetic diagnosis has become increasingly common and controversial with time. The big question centers around where the line should be drawn regarding such testing, with many opposed to sex selection via these means. For a good overview on this topic, read Robertson’s article “Extending preimplantation genetic diagnosis: The ethical debate” (full citation below). Share information from this article, and any other information you gather, with your class. Then hold a discussion on the topic. Robertson, J.A. (2003). Extending preimplantation genetic diagnosis: The ethical debate. Human Reproduction, 18, 465-471. 3. The Cesarean section controversies. The textbook does not cover Cesarean sections, but with them now accounting for about a third of all U.S. deliveries, they are a prime topic for lecture and discussion. Conduct some Internet research to collect up-to-date statistics on the current rate of C-sections in America, how this rate relates to that of other industrialized nations, and how the rate has changed over time. Tell your students how and why C-sections are conducted. Also explain the risks associated with C-sections. Then ask your students whether they think it is problematic that C-sections are becoming increasingly common in America. To further discussion, ask whether they think elective C-sections are acceptable and why they believe as they do. The following websites may be helpful references as you gather information for this lecture and discussion: http://www.cdc.gov/nchs/fastats/delivery.htm http://www.marchofdimes.com/pregnancy/csection_indepth.html http://www.americanpregnancy.org/labornbirth/cesareanrisks.html http://www.childbirthconnection.org/article.asp?ck=10456 IN-CLASS ACTIVITIES Demonstrations 1. Invite a genetic counselor to class. A great way to make genetics come alive for students is to have a genetic counselor come to class and speak about her experiences with clients. Ask him or her to bring in a number of case studies (real cases with identifying details changed, if possible) that can be shared with the class. This should spark conversation about the difficult choices parents, or prospective parents, sometimes have to make. The genetic counselor may also talk about the ethics involved in the counseling process and how referrals occur. In addition, this guest speaker can be an excellent opportunity for a brief discussion about careers. What is the genetic counselor’s educational background? What credentials are needed for a job in the field? Would psychology students be good candidates for such a path? 2. See inside the womb. A fantastic insight into the life of the zygote, embryo, and fetus are provided by National Geographic’s documentary In the Womb. The program is widely available for purchase on DVD. Using a combination of real photography, 3D and 4D ultrasound images, and computer-generated images, the documentary walks the viewer through the entire prenatal process, emphasizing changes and experiences the developing organism undergoes. The 19 Chapter 2 documentary also discusses fetal surgery. The program is highly engaging and entertaining in addition to being informative. Share this video with your class and then hold a discussion about the elements that they found to be surprising or particularly noteworthy. What do they understand after watching the video that they did not comprehend from just reading the textbook? If your students show a strong interest in this video, you could lead them to the followup documentaries that National Geographic produced: Animals in the Womb, In the Womb: Multiples, In the Womb: Identical Twins, In the Womb: Dogs, and In the Womb: Cats. 3. Teratogens and their effects on the developing brain. The Annenberg Foundation provides a variety of high-quality videos streaming online for free. One of these videos, part of The Mind series, discusses how alcohol, drugs, and environmental teratogens affect the brain of a developing human. Using visuals of the developing embryo, brain slices from autopsies, and interviews with leading scientists, this video provides a compelling portrayal of how detrimental teratogens can be to development. The video called “Teratogens and Their Effects on the Developing Brain and Mind” is available at http://www.learner.org/resources/series150.html. 4. The anatomy of childbirth. PBS’s Nova offers an interactive website that shows the stages of childbirth, the risks that can occur in each stage, and the treatment for any complications. You can share this site using a computer and a connected overhead projector. The information can be found at http://www.pbs.org/wgbh/nova/body/anatomy-childbirth.html. Small Group Activities/Role-Plays/Simulations 1. Genetic diseases. The textbook mentions a handful of genetic diseases (e.g., sickle-cell anemia and cystic fibrosis), but there are, of course, many more. In groups of 2 to 3 students, spend some time exploring the website of the Human Genome Project to learn more about genetic diseases. You might start at http://www.ornl.gov/sci/techresources/Human_Genome/medicine/assist.shtml. Write down key information about genetic diseases, genetic testing, and ethics. Be prepared to share this information with your class. 2. Are reproductive technologies ethical? The “Linking Research to Life” box contains a great deal of information about reproductive technologies. In groups of 3 to 4 students, have a discussion about the ethics of these technologies. You might address the following questions: Are reproductive technologies like IVF inherently unethical? Why or why not? Should women who are too old to conceive children without reproductive technologies be allowed to use these technologies? Why or why not? Should parents be allowed to choose an embryo based on its genetic profile? Are certain instances OK (e.g., to screen for genetic diseases) and others not (e.g., to choose physical features like height or hair color)? Should there be a limit to how many embryos are implanted in a woman? Should this be legally imposed or just a recommended guideline? When answering, keep in mind the low rate of success of such procedures (hence the desire to implant more embryos). Is it acceptable that a baby could have five “parents”? Why do you think as you do? Should surrogacy be allowed? Why or why not? 20 Full file at http://testbank360.eu/test-bank-essentials-of-human-development-1st-edition-kail 3. Understanding prenatal development. In groups of 2 to 3 students, complete Handout 2-2, The Periods of Prenatal Development. This handout assesses your understanding of what occurs during each stage of prenatal development. When you’re done, check your work against the textbook. 4. You’re pregnant! Now what? Pair up with a classmate. Now imagine that each of you, or each of your sexual partners, has just gotten a positive pregnancy test. Assume that you are at a point in your life where you desire to keep the pregnancy and raise the child. As a team, create a detailed plan for the pregnancy. Write down what you should avoid and when to avoid it (if applicable). Also write down what you should be sure to do. To make your plan particularly strong, conduct an Internet search to include information that goes beyond that presented in the textbook. While creating your plan, keep the stages of prenatal development firmly in mind. That is, some advice will be more applicable during certain periods than others; be sure to indicate this. OUTSIDE THE CLASSROOM ACTIVITIES Projects 1. Down syndrome. Down syndrome affects many individuals and becomes more likely to occur with increased maternal age. The National Down Syndrome Society has a host of resources for families affected by Down syndrome. Spend time conducting research on its website, http://www.ndss.org, and then write a three-page paper on what you have learned. You can write about anything that you find particularly compelling, disturbing, or otherwise noteworthy. After perusing this site, what are your thoughts about prenatal testing for Down syndrome? Remember that not all women who receive a prenatal diagnosis of Down syndrome choose to abort; some use this information simply to help themselves get prepared. 2. How genes affect behavior. Complete Handout 2-1, Paths from Genes to Behaviors. The handout asks you to provide examples for the general properties we know about how genes affect behaviors. 3. What was your prenatal and perinatal period like? For this project, interview your parents about what it was like when your mother was pregnant with you, and how the labor and delivery process proceeded. Were there any complications at any point? During pregnancy, did your mother take the precautions against teratogens that the textbook recommends, or were these recommendations not known at the time? Did your parents take childbirth preparation classes? If so, what did these entail? Did your mother choose to have pain medication during labor? Why or why not? Were you of a normal birth weight, and were you born on time? Ask these and other questions and then write a two-page paper about your “early days.” If you do not have access to your birth parents, instead write a paper about your entry into your current family’s life, whether it be through adoption or some other means. 4. Alternative childbirth processes. The textbook mentions prepared or natural childbirth techniques, but there are many other childbirth approaches available to families who are expecting. Not only are there many types of preparation classes, there are also a variety of birthing settings (e.g., home, hospital, birthing center) and options for whom can be present at the birth (e.g., obstetrician, midwife, doula). Using information you’ve gleaned from searching the Internet, write a three-page paper about the options available to expectant couples. Do any seem particularly appealing to you? Why? 21 Chapter 2 5. Low birth weight. To reinforce and expand your understanding of the risks and causes of low birth weight, complete Handout 2-3. This handout requires you to both make use of your textbook and conduct some additional Internet research. Journal Prompts 1. Your bias toward or against the study of genetics. Chances are that Chapter 2 is not your first introduction to the mechanisms of heredity and other information about genetics. Often, our first encounters with such material are dry and unrelated to our everyday lives. If so, we may carry resistance to the topic. On the other hand, perhaps your early introduction to the study of genetics was engaging and thought-provoking. Write a journal entry that delves into your own thoughts and experiences with the study of genetics. Are you resistant, or are you eager to learn more? What might you do to become more interested, if you sense a resistance within yourself? Does the relation to human development make the topic more palatable? Given that genetics are key to a developmental psychology class (nature-nurture), this is an important issue to resolve. 2. Your thoughts about pregnant women. Have you ever seen a pregnant woman doing something that you thought she shouldn’t be doing? Perhaps walking in high heels or drinking an alcoholic beverage or going out for a run or using her cell phone? Have you ever considered intervening (or have actually done so)? Why or why not? Knowing what you do now from reading Chapter 2, were the behaviors you witnessed actually dangerous, or did you simply perceive them as such? [If Chapter 2 didn’t address the particular behavior you saw, do a quick Internet search to see if there is any cause for actual concern (e.g., running during pregnancy is generally regarded as safe, as long as the woman was physically fit before becoming pregnant).] Will you be more alert to the behavior of pregnant women in the future, do you think? 3. Childbirth preparation classes. It’s impossible to know for sure what decisions you’ll make in the future until you get there. Knowing what you know now, though, do you think that you would take childbirth preparation classes when expecting your first child? Why or why not? Do you think that your gender influences your answer? Should it? After all, a supportive “coach” is key to prepared childbirth techniques. Write a journal entry addressing these questions and any related thoughts that emerge. HUMAN DEVELOPMENT IN ACTION Here are sample answers to the “Human Development in Action” questions that appear in the margins of the textbook. 1. Imagine that you are a genetic counselor. Your client is a young woman whose father has cystic fibrosis, an inherited disease in which the lungs fill with mucous, making breathing difficult. Cystic fibrosis is caused by a recessive gene, and your client wonders whether her baby will inherit the disease. Sample Answer: Like the example in the textbook about sickle-cell disease, only if the client’s baby inherits two recessive alleles for cystic fibrosis is the baby likely to develop the disease. If no one in the client’s partner’s family has had cystic fibrosis, the partner almost certainly has two alleles that do not carry cystic fibrosis. Thus it is important to investigate the genetic history of the client’s partner. 22 Full file at http://testbank360.eu/test-bank-essentials-of-human-development-1st-edition-kail 2. Suppose you’re a nurse caring for a baby born 26 weeks after conception. Describe the main challenges that the baby faces. Sample Answer: Babies born this early have trouble breathing because their lungs are not yet mature and they don’t regulate their body temperature well because they lack body fat that provides insulation. The baby may have additional problems depending on how low his or her birth weight was. 3. Suppose that you’re a healthcare professional meeting with Chloe from the section-opening vignette. Return to her questions and answer them for her. Sample Answer: Chloe had three questions. Here they are, in Q&A format: Q: “I use my cell phone a lot. Is radiation from the phone harmful to my baby?” A: More research is needed to answer this question adequately. The current best advice for a pregnant woman is to keep a cell phone at a distance when it’s not being used and never use it while driving. Q: “At night, my husband and I have a glass of wine to help unwind from the stress of the day. Is light drinking like this okay?” A: We do not yet know if there is any safe amount of alcohol for pregnant women to consumer. The best policy is for women to avoid all drugs throughout pregnancy. Q: “I’m 38. I know older women give birth to babies with mental retardation more often. Can I know if my baby will be mentally retarded?” A: Amniocentesis and chorionic villus sampling can detect the presence of Down syndrome. The odds that a woman will bear a child with Down syndrome increase markedly as she gets older, from about 1 in 1,000 during her 20s to 1 in 50 during her 40s. 4. A 24-year-old who is pregnant for the first time thinks that childbirth preparation classes seem like a waste of time. As a healthcare professional, what would you say to convince her that these classes are worthwhile? Sample Answer: Childbirth preparation classes help individuals understand what will happen during the labor and delivery process. They also emphasize how to deal with pain without using medication, which is positive because pain-reducing drugs can affect the baby and make it difficult for the mother to push the baby through the birth canal. LINKING RESEARCH TO LIFE Conception in the 21st Century After students have read the “Linking Research to Life” section of the text, have them answer the following questions: Who was the first person conceived in a petri dish? What happens during in vitro fertilization? How many “parents” can a baby have? Explain why. Do children conceived from reproductive technologies have developmental difficulties? What are the issues that reproductive technologies can cause? What ethical issues surround reproductive technologies? What is eugenics? How does this concept relate to reproductive technologies? 23 Chapter 2 How does maternal age factor into reproductive technologies? What are your thoughts on reproductive technologies? Should there be limits to its use? If so, when and why? KEY TERMS chromosomes autosomes sex chromosomes deoxyribonucleic acid (DNA) gene genotype phenotype alleles homozygous heterozygous dominant recessive polygenic inheritance monozygotic twins dizygotic twins niche-picking nonshared environmental influences prenatal development zygote implantation germ disc 24 placenta embryo amnion amniotic fluid umbilical cord period of the fetus age of viability teratogen fetal alcohol spectrum disorder ultrasound amniocentesis chorionic villus sampling fetal medicine hypoxia preterm (premature) low birth weight very low birth weight extremely low birth weight infant mortality in vitro fertilization eugenics HANDOUT 2-1: PATHS FROM GENES TO BEHAVIOR Below are the general known properties of how genes affect behavior. After each property, write three examples, either from your real-world experiences or from your acquired knowledge. 1. Heredity and environment interact dynamically throughout development. - - - 2. Genes can influence the kind of environment to which a person is exposed. - - - 3. Environmental influences typically make children within a family different. - - - 25 HANDOUT 2-2: THE PERIODS OF PRENATAL DEVELOPMENT Indicate in which period of prenatal development the items listed in the left column occur. Period of the Zygote Period of the Embryo Differentiation of cells marks the end of this period. The mother feels movement. Specialization of cells occurs. The germ disc forms. Implantation occurs. The finishing touches are placed on many systems essential to human life. The final and longest phase of prenatal development. All regions of the brain grow, particularly the cerebral cortex. The developing baby has reached the age of viability. The nuclei of the egg and sperm fuse, and the two independent sets of 23 chromosomes are interchanged. Fertilization takes place. Body structures and internal organs develop. The organism first links to the mother via the umbilical cord. 26 Period of the Fetus HANDOUT 2-3: LOW BIRTH WEIGHT Complete this handout to reinforce your understanding of low-birth-weight babies. The first four questions can be answered using information from the textbook. Questions 5 and 6 require additional research. 1. What are the weights associated with each of the following categories? a. Low birth weight: b. Very low birth weight: c. Extremely low birth weight: 2. What are the specific problems that very low-birth-weight and extremely low-birth-weight babies typically have? 3. What services are often provided in the hospital for babies who weigh more than 1,500 grams? 4. What services are often provided after the hospital for babies who weigh more than 1,500 grams? 5. Based on research you conduct on the Internet, what are the risk factors for having a baby with some degree of low birth weight? 6. Based on research you conduct on the Internet, what can be done to help prevent low birth weight? 27