Test Bank for HDEV, 6th Edition

Name: Class: Date: Chapter 2 – Heredity and Prenatal Development 1. Sebaceous glands cause a developing organism to grow arms or wings, skin or scales. a. True b. False ANSWER: False 2. Typical human cells contain 50 chromosomes organized into 25 pairs. a. True b. False ANSWER: False 3. Meiosis is responsible for the production of sperm and ova. a. True b. False ANSWER: True 4. Monozygotic (MZ) twins are known as fraternal twins. a. True b. False ANSWER: False 5. Dizygotic (DZ) twins run in families. a. True b. False ANSWER: True 6. As women reach the end of their childbearing years, ovulation becomes more regular. a. True b. False ANSWER: False 7. The probability of having a child with Down’s syndrome increases with the age of the parents. a. True b. False ANSWER: True 8. Duchenne muscular dystrophy is a sex-linked abnormality. a. True b. False ANSWER: True 9. Color blindness is a sex-linked abnormality. a. True b. False ANSWER: True Copyright Cengage Learning. Powered by Cognero. Page 1 Name: Class: Date: Chapter 2 – Heredity and Prenatal Development 10. Amniocentesis is a procedure used in abortion. a. True b. False ANSWER: False 11. Neural tube defects cause an elevation in the alpha-fetoprotein (AFP) level in the mother’s blood. a. True b. False ANSWER: True 12. The actual sets of traits that people exhibit are called their genotypes. a. True b. False ANSWER: False 13. Genotypes reflect both genetic and environmental influences. a. True b. False ANSWER: False 14. Sperm are much larger than ova. a. True b. False ANSWER: False 15. A low sperm count, or lack of sperm, is the most common infertility problem in men. a. True b. False ANSWER: True 16. A blastocyst gains mass only when it receives nourishment from outside. a. True b. False ANSWER: True 17. The fetus begins to turn and respond to external stimulation at about the second or third week. a. True b. False ANSWER: False 18. The mother usually feels the first fetal movements during the first month of pregnancy. a. True b. False ANSWER: False Copyright Cengage Learning. Powered by Cognero. Page 2 Name: Class: Date: Chapter 2 – Heredity and Prenatal Development 19. Rh incompatibility occurs when an Rh-positive woman is carrying an Rh-negative fetus. a. True b. False ANSWER: False 20. Babies with fetal alcohol syndrome (FAS) are often larger than normal, and so are their brains. a. True b. False ANSWER: False 21. The field of biology that studies heredity is called: a. etiology. b. ecology. c. genetics. d. eugenics. ANSWER: c 22. Chromosomes are _____ structures found in cells. a. rod-shaped b. circular c. cone-shaped d. octagonal ANSWER: a 23. Chromosomes contain thousands of segments called: a. nuclei. b. nodes. c. capillaries. d. genes. ANSWER: d 24. Which of the following most accurately describes the function of genes? a. They regulate the development of traits. b. They prevent foreign particles from entering the body. c. They work together with lutein to influence development. d. They transfer oxygen from the bloodstream to other parts of the body. ANSWER: a 25. Polygenic traits are those that are: a. developed during adolescence. b. transmitted by the mother. c. uncommon in humans. d. determined by several pairs of genes. ANSWER: d Copyright Cengage Learning. Powered by Cognero. Page 3 Name: Class: Date: Chapter 2 – Heredity and Prenatal Development 26. Deoxyribonucleic acid (DNA) takes the form of a: a. single spiral. b. double helix. c. sphere. d. cube. ANSWER: b 27. Which of the following pairs of bases is present in the rungs of the ladder-like structure of deoxyribonucleic acid (DNA)? a. Cytosine with guanine b. Rhodamine with biotin c. Diaminopurine with ribozyme d. Serine with tyrosine ANSWER: a 28. Humans begin life as a single cell that divides repeatedly. This cell is known as a(n): a. zygote. b. gonadotrope. c. embryo. d. chromaffin. ANSWER: a 29. In the structure of deoxyribonucleic acid (DNA), which of the following bases combines with thymine? a. Cytosine b. Adenine c. Rhodamine d. Serine ANSWER: b 30. Which of the following processes happen during mitosis? a. Strands of deoxyribonucleic acid (DNA) break apart. b. Adenine combines with its appropriate partner, cytosine. c. Sperm and ova cells are created. d. Twenty-three chromosomes are created. ANSWER: a 31. Which of the following statements is true of mutations? a. Mutations can only occur by chance. b. Mutations produce sperm and ova cells. c. Mutations occur through radiation or other environmental influences. d. Mutations help adenine combine with guanine to form the single spiral structure of deoxyribonucleic acid (DNA). ANSWER: c Copyright Cengage Learning. Powered by Cognero. Page 4 Name: Class: Date: Chapter 2 – Heredity and Prenatal Development 32. After meiosis, each new cell nucleus contains _____ chromosomes. a. 46 b. 35 c. 23 d. 12 ANSWER: c 33. A human zygote contains _____ pairs of autosomes. a. 46 b. 44 c. 23 d. 22 ANSWER: d 34. The determination of a child’s sex depends on the: a. presence of teratogens at the time of conception. b. sex chromosome received from the mother. c. presence of teratogens at the time of ovulation. d. sex chromosome received from the father. ANSWER: d 35. The typical sex chromosome pattern for males is _____. a. XX b. XYY c. XY d. XXY ANSWER: c 36. The typical sex chromosome pattern for females is _____. a. XX b. XYY c. XY d. XXY ANSWER: a 37. Twins that derive from a single zygote that has split into two are called: a. monozygotic (MZ) twins. b. non-identical twins. c. fraternal twins. d. dizygotic (DZ) twins. ANSWER: a 38. According to a study in the year 2013 by Fellman, if a woman is a twin, if her mother was a twin, or if she has previously borne twins, then: Copyright Cengage Learning. Powered by Cognero. Page 5 Name: Class: Date: Chapter 2 – Heredity and Prenatal Development a. she will bear only monozygotic (MZ) twins. b. the chances of her becoming pregnant decrease. c. she is likely to be a healthy mother. d. the chances rise that she will bear twins. ANSWER: d 39. According to a study in the year 2013 by Fellman, the chances of twins: a. increase when a woman conceives before she is 21. b. increase with parental age. c. decrease with the number of times couples have sex before conception. d. decrease with the use of fertility drugs. ANSWER: b 40. According to a study in the year 2013 by Fellman, which of the following statements is true of fertility drugs? a. They enhance the chances of multiple births. b. They stop ova from ripening. c. They should be taken orally and not injected. d. They suppress the process of hormone secretion. ANSWER: a 41. Each member of a pair of genes is termed a(n) _____. a. allele b. zygote c. autosome d. node ANSWER: a 42. When both of the alleles for a trait, such as hair color, are the same, the person is said to be _____ for that trait. a. monozygotic b. dizygotic c. homozygous d. hemizygous ANSWER: c 43. When the effects of both alleles are shown, there is said to be: a. codominance. b. preponderance. c. ascendance. d. concurrence. ANSWER: a 44. If an individual gets a recessive gene for eye color from both parents, the: a. gender of the child will determine if that trait is shown. b. recessive trait will develop in the child. Copyright Cengage Learning. Powered by Cognero. Page 6 Name: Class: Date: Chapter 2 – Heredity and Prenatal Development c. recessive trait will develop 50% of the time. d. recessive trait will be suppressed, and the dominant trait will be expressed. ANSWER: b 45. Jill bears the genetic code for Von Willebrand disease, but she has never developed the illness herself. Jill would be considered: a. a carrier of the recessive gene that causes the disease. b. susceptible to the disease after adolescence. c. an acceptor of the recessive gene that causes the disease. d. susceptible to the disease at late adulthood. ANSWER: a 46. Which of the following statements is considered a multifactorial problem? a. Cystic fibrosis b. Down’s syndrome c. Diabetes mellitus d. XYY syndrome ANSWER: c 47. Down’s syndrome is caused by: a. alcohol abuse by the mother at the time of conception. b. sex-linked chromosomal abnormalities. c. an extra chromosome on the 21st pair. d. drug abuse by the mother during pregnancy. ANSWER: c 48. Which of the following statements is true of Down’s syndrome? a. Down’s syndrome is usually caused by a defect in the sex chromosomes of an individual. b. The symptoms of Down’s syndrome are similar to those of sickle-cell anemia. c. Down’s syndrome is caused by a sexually transmitted infection (STI) during conception. d. The probability of having a child with Down’s syndrome increases with the age of the parents. ANSWER: d 49. According to a study in 2013 by van Gameren-Oosterom, individuals with Down’s syndrome: a. are unlikely to die from cardiovascular problems by middle age. b. have no specific characteristic features. c. show deficits in cognitive development. d. are likely to have only 46 chromosomes. ANSWER: c 50. Which of the following statements is a characteristic of supermales? a. They are somewhat taller than average. b. Their facial hair growth is minimal when compared to normal males. c. They suffer from gynecomastia. Copyright Cengage Learning. Powered by Cognero. Page 7 Name: Class: Date: Chapter 2 – Heredity and Prenatal Development d. They are typically impotent. ANSWER: a 51. Twenty-year-old Jack is extremely tall and has very thick facial hair. Most of his male secondary sex characteristics are also more pronounced than men of his age. In this scenario, Jack is most likely: a. an XYY male. b. to be diagnosed with Klinefelter syndrome. c. an XXY male. d. to be diagnosed with Down’s syndrome. ANSWER: a 52. According to a study in 2014 by Skakkebaek et al., who among the following is most likely to have gynecomastia? a. Jennifer, a dancer, who has Down’s syndrome b. Frank, a teacher, who is diagnosed with XYY syndrome c. Peter, a fashion designer, who has Klinefelter syndrome d. Ria, a gym instructor, who is diagnosed with Turner syndrome ANSWER: c 53. Individuals with Klinefelter syndrome produce: a. less estrogen than normal males. b. less testosterone than normal males. c. less adenine than normal males. d. less thymine than normal males. ANSWER: b 54. Rico is a man who has enlarged breasts and suffers from mild mental retardation. He has a problem learning languages, and his body produces less of the male sex hormone testosterone than normal males. Rico is most likely suffering from: a. Klinefelter syndrome. b. Tay-Sachs disease. c. Turner syndrome. d. Down’s syndrome. ANSWER: a 55. Tim, a 27-year-old man, has unusually narrow shoulders, low muscle mass, and has no facial and body hair. His doctor recently prescribed testosterone replacement therapy to him. Tim is most likely suffering from: a. phenylketonuria (PKU). b. cystic fibrosis. c. Klinefelter syndrome. d. Huntington’s disease (HD). ANSWER: c 56. Girls with Turner syndrome: a. possess more thymine than cytosine. b. are taller than average. Copyright Cengage Learning. Powered by Cognero. Page 8 Name: Class: Date: Chapter 2 – Heredity and Prenatal Development c. produce little estrogen. d. are more likely to give birth to twins. ANSWER: c 57. Daisy was always unusually short for her age. She was unable to conceive a child after marriage, and upon visiting a doctor, she was prescribed estrogen replacement therapy. Daisy is most likely suffering from: a. phenylketonuria (PKU). b. cystic fibrosis. c. Turner syndrome. d. Huntington’s disease (HD). ANSWER: c 58. Matt is a 36-year-old male. In the past year, he has noticed that his limbs sometimes move on their own, and he has also started having trouble remembering things and doing simple calculations. Matt’s father and grandfather were also known to have similar problems during their adulthood. Matt is most likely suffering from: a. phenylketonuria (PKU). b. cystic fibrosis. c. Turner syndrome. d. Huntington’s disease (HD). ANSWER: d 59. Sickle-cell anemia is caused by: a. a chromosomal abnormality. b. a single segment found only on the Y chromosome. c. a recessive gene. d. a decrease in estrogen levels. ANSWER: c 60. Which of the following statements is true of sickle-cell anemia? a. It is typically treated with testosterone replacement therapy. b. Children with this problem cannot metabolize an amino acid called phenylalanine. c. It leads to the obstruction of small blood vessels and decreased oxygen supply. d. Girls with this problem are shorter than average and infertile. ANSWER: c 61. Which of the following is most likely to develop sickle cell anemia? a. European American. b. Native American. c. African American. d. Asian American. ANSWER: c 62. Which of the following illnesses causes a degeneration of the central nervous system? a. Tay-Sachs disease Copyright Cengage Learning. Powered by Cognero. Page 9 Name: Class: Date: Chapter 2 – Heredity and Prenatal Development b. Cystic fibrosis c. Turner syndrome d. Klinefelter syndrome ANSWER: a 63. Which of the following statements is true about Tay-Sachs disease? a. it is most commonly found among children in Jewish families of Eastern European background. b. Children who have this disease suffer from excessive production of mucus in the lungs and pancreas. c. It is most commonly found among children in Asian American families. d. Children who have this disease suffer from muscular dystrophy characterized by a weakening of the muscles. ANSWER: a 64. Cystic fibrosis is caused by a(n): a. sex-linked abnormality. b. abnormality in the 21st pair of chromosomes. c. recessive gene. d. single segment found only on the Y chromosome. ANSWER: c 65. Which of the following statements is a symptom of cystic fibrosis in children? a. Cystic fibrosis leads to uncontrollable muscle movements and personality change. b. Cystic fibrosis leads to the excessive production of thick mucus that clogs the pancreas and lungs. c. Cystic fibrosis causes red blood cells to clump together, obstructing small blood vessels and decreasing the oxygen supply. d. Cystic fibrosis causes the central nervous system to degenerate, resulting in death. ANSWER: b 66. Most victims of _____ die of respiratory infections in their 20s. a. Tay-Sachs disease b. cystic fibrosis c. Turner syndrome d. Klinefelter syndrome ANSWER: b 67. Which of the following statements is a symptom of cystic fibrosis in children? a. They suffer from a genetic disorder that decreases the blood’s capacity to carry oxegen. b. They suffer from excessive production of thick mucus that clogs the pancreas and lungs. c. They suffer from a loss of intellectual functioning and personality change. d. They produce less of the male sex hormone testosterone than normal children. ANSWER: b 68. A(n) _____ is a procedure for using ultrasonic sound waves to create a picture of an embryo or fetus. a. phenotype b. sonogram Copyright Cengage Learning. Powered by Cognero. Page 10 Name: Class: Date: Chapter 2 – Heredity and Prenatal Development c. genotype d. alpha-fetoprotein (AFP) assay ANSWER: b 69. _____ is used to detect neural tube defects such as spina bifida and certain chromosomal abnormalities. a. Artificial insemination b. Amniocentesis c. Endometriosis d. Alpha-fetoprotein (AFP) assay ANSWER: d 70. An individual’s _____ reflects both genetic and environmental influences. a. phenotype b. chromosome c. allele d. genotype ANSWER: a 71. Who among the following share 100% of their genes? a. Biovular twins b. Fraternal twins c. Dizygotic (DZ) twins d. Monozygotic (MZ) twins ANSWER: d 72. When children who are reared by adoptive parents are nonetheless more similar to their natural parents in a trait, it can be concluded that: a. the genetic characteristics of the children change over time. b. heredity is solely responsible for how a child grows. c. the environment is solely responsible in the development of those characteristics. d. genetics play a role in the development of those characteristics. ANSWER: d 73. According to a survey by Adhikari and Liu in the year 2013, at birth, women have: a. close to 100,000 ova. b. around 300,000 to 400,000 ova. c. around 100 to 200 ova. d. only 500 ova. ANSWER: b 74. Which of the following statements is true of menstruation? a. During this time, the endometrium is not discharged. b. During this time, an unfertilized egg is discharged. c. During this time, a female cannot have sex with her partner. Copyright Cengage Learning. Powered by Cognero. Page 11 Name: Class: Date: Chapter 2 – Heredity and Prenatal Development d. During this time, a fertilized egg undergoes mitosis. ANSWER: b 75. Before meiosis, a sperm cell: a. contains 46 chromosomes. b. contains two X chromosomes. c. is significantly larger than an egg cell. d. contains both an X and a Y chromosome. ANSWER: a 76. Which of the following statements is true of a sperm cell? a. A sperm cell is significantly larger than an egg cell. b. A sperm cell contains two Y chromosomes. c. A sperm cell travels randomly inside a woman’s reproductive tract. d. A sperm cell is one of the smallest types of cells in the body. ANSWER: d 77. In the context of an average ejaculation, which of the following statements is true about sperm? a. The average count of sperm in the ejaculate is 2.5 billion. b. Sperm in the ejaculate find the ovum by following the current of the fluid coming from the cervix. c. Only 1 in 1,000 sperm in the ejaculate will ever approach an ovum. d. Most of the sperm in the ejaculate move about in a random pattern in the vagina. ANSWER: c 78. Once the testes have developed in the embryo, they begin to produce male sex hormones, or _____. a. androgens b. genotypes c. blastocysts d. teratogens ANSWER: a 79. The _____ is the inner layer of the embryo from which the lungs and digestive system develop. a. neural tube b. mesoderm c. endoderm d. umbilical cord ANSWER: c 80. The _____ is the central layer of the embryo from which the bones and muscles develop. a. neural tube b. mesoderm c. ectoderm d. umbilical cord ANSWER: b Copyright Cengage Learning. Powered by Cognero. Page 12 Name: Class: Date: Chapter 2 – Heredity and Prenatal Development 81. _____ are environmental agents that can harm the embryo or fetus. a. Mutations b. Autosomes c. Teratogens d. Androgens ANSWER: c 82. Which of the following happens in the critical period that occurs in the fourth through eighth weeks of a pregnancy? a. The development of the lungs b. The development of the heart c. The development of arms and legs d. The development of the stomach ANSWER: c 83. _____ is a synthetic hormone used to prevent miscarriages that can cause masculinization of the fetus. a. Testosterone b. Estrogen c. Progestin d. Oxytocin ANSWER: c 84. _____ was a drug marketed in the 1960s to pregnant women that caused birth defects such as missing or stunted limbs in infants. a. Progestin b. Estrogen c. Thalidomide d. Oxytocin ANSWER: c 85. _____ is a type of estrogen, prescribed in the 1940s and 1950s to pregnant women, that is said to have caused testicular, vaginal, and cervical cancer in some offspring. a. Androsterone b. Adiponectin c. Progestin d. Diethylstilbestrol ANSWER: d 86. _____ is a sexually transmitted infection that, in advanced stages, can attack major organ systems. a. Rubella b. Syphilis c. Cystic fibrosis d. Phenylketonuria ANSWER: b Copyright Cengage Learning. Powered by Cognero. Page 13 Name: Class: Date: Chapter 2 – Heredity and Prenatal Development 87. _____, also called German measles, is a viral infection passed on from the mother to the fetus that can cause birth defects such as deafness, intellectual disabilities, blindness, and heart disease in the embryo. a. Rubella b. Syphilis c. Cystic fibrosis d. Phenylketonuria ANSWER: a 88. _____ is a life-threatening disease, characterized by high blood pressure that may afflict women late in the second or early in the third trimester. a. Rubella b. Syphilis c. Preeclampsia d. Phenylketonuria ANSWER: c 89. Which of the following statements about Rh incompatibility is true? a. Rh incompatibility occurs most commonly during a woman’s first pregnancy. b. Rh incompatibility is an untreatable condition that leaves a woman infertile for the rest of her life. c. Rh incompatibility is an abnormality that is transmitted from generation to generation and carried by a sex chromosome. d. Rh incompatibility occurs due to antibodies transmitted to a fetus during subsequent deliveries causing brain damage or death. ANSWER: d 90. Thalidomide was marketed in the 1960s as a treatment for: a. insomnia and nausea. b. infertility and impotency. c. Down’s syndrome. d. Turner Syndrome. ANSWER: a 91. _________ is the process in which the double helix of deoxyribonucleic acid (DNA) duplicates. a. Amniocentesis b. Mitosis c. Meiosis d. Mutation ANSWER: b 92. After mitosis, the genetic code is identical in new cells unless _________ occur through radiation or other environmental influences. a. reductions b. expulsions Copyright Cengage Learning. Powered by Cognero. Page 14 Name: Class: Date: Chapter 2 – Heredity and Prenatal Development c. conceptions d. mutations ANSWER: d 93. _________ are problems that stem from the interaction of heredity and environmental factors. a. Multifactorial problems b. Cognitive problems c. Horizon problems d. Coronal problems ANSWER: a 94. _________ is a fatal genetic neurologic disorder whose onset is in middle age. a. Tay-Sachs disease b. Duchenne muscular dystrophy c. Hemophilia d. Huntington’s disease ANSWER: d 95. _________ is a genetic disorder in which blood does not clot properly. a. Cystic fibrosis b. Hemophilia c. Lymphoma d. Huntington’s disease ANSWER: b 96. The _________ is the hollow organ within females in which the embryo and fetus develop. a. placenta b. ovum c. uterus d. amniotic sac ANSWER: c 97. Monozygotic (MZ) twins share _________ percent of their genes. a. 100 b. 75 c. 50 d. 25 ANSWER: a 98. Dizygotic (DZ) twins share _________ percent of their genes. Copyright Cengage Learning. Powered by Cognero. Page 15 Name: Class: Date: Chapter 2 – Heredity and Prenatal Development a. 100 b. 75 c. 50 d. 25 ANSWER: c 99. _________ is self-propulsion. a. Mitosis b. Meiosis c. Motility d. Mutation ANSWER: c 100. The embryo and fetus develop within a protective_________ in the uterus. a. amniotic sac b. umbilical cord c. neural tube d. embryonic disk ANSWER: a 101. Distinguish between monozygotic (MZ) twins and dizygotic (DZ) twins. ANSWER: Now and then, a zygote divides into two cells that separate so that each develops into an individual with the same genetic makeup. These individuals are identical twins, or monozygotic (MZ) twins. If the woman produces two ova in the same month and they are each fertilized by different sperm cells, they develop into fraternal twins, or dizygotic (DZ) twins. DZ twins run in families. If a woman is a twin, if her mother was a twin, or if she has previously borne twins, the chances rise that she will bear twins. 102. Describe the symptoms and conditions of a child with Down’s syndrome. ANSWER: Answers will vary. Down’s syndrome is usually caused by an extra chromosome on the 21st pair, resulting in 47 chromosomes. The probability of having a child with Down’s syndrome increases with the age of the parents. People with Down’s syndrome have characteristic features that include a rounded face, a protruding tongue, a broad, flat nose, and a sloping fold of skin over the inner corners of the eyes. They show deficits in cognitive development and motor development and usually die from cardiovascular problems by middle age, although modern medicine has extended life appreciably. 103. Distinguish between Klinefelter syndrome and Turner syndrome. ANSWER: Answers will vary. Approximately 1 male in 500 has Klinefelter syndrome, which is caused by an extra X sex chromosome (an XXY sex chromosomal pattern). XXY males produce less of the male sex hormone testosterone than normal males. As a result, male primary and secondary sex characteristics—such as the testes, deepening of the voice, musculature, and the male pattern of body hair—do not develop properly. XXY males usually have enlarged breasts (gynecomastia) and are usually mildly mentally retarded, particularly in language skills. XXY males are typically treated with testosterone replacement therapy, which can foster growth of sex characteristics and elevate the mood, but they remain infertile. Approximately 1 girl in 2,500 has a single X sex chromosome and, as a result, develops Turner syndrome. The external genitals of such girls are normal, but their ovaries are poorly developed, and they produce little estrogen. Girls with this problem are shorter than average and infertile. Researchers have connected a Copyright Cengage Learning. Powered by Cognero. Page 16 Name: Class: Date: Chapter 2 – Heredity and Prenatal Development specific pattern of cognitive deficits with low estrogen levels: problems in visual-spatial skills, mathematics, and nonverbal memory. 104. Discuss the cause and symptoms of Huntington’s disease (HD). ANSWER: Answers will vary. Huntington’s disease (HD) is a fatal, progressive degenerative disorder and a dominant trait, affecting approximately 1 American in 18,000. Physical symptoms include uncontrollable muscle movements. Psychological symptoms include loss of intellectual functioning and personality change (van Dujin et al., 2014). Because the onset of HD is delayed until middle adulthood, many individuals with the defect have borne children only to discover years later that they and possibly half their offspring will inevitably develop it. Medicines can help deal with some symptoms. 105. Why is amniocentesis carried out on pregnant women? ANSWER: Answers will vary. Amniocentesis is usually performed on the mother at 14-16 weeks after conception, although many physicians now perform the procedure earlier (“early amniocentesis”). In this fetal-screening method, the health professional uses a syringe (needle) to withdraw fluid from the amniotic sac. The fluid contains cells that are sloughed off by the fetus. The cells are separated from the amniotic fluid, grown in a culture, and then examined microscopically for genetic and chromosomal abnormalities. 106. What were the conclusions of kinship studies? ANSWER: Answers will vary. Researchers study the distribution of a trait or behavior among relatives who differ in the degree of genetic closeness. The more closely people are related, the more genes they have in common. Parents and children have a 50% overlap in their genetic endowments, and so do siblings (brothers and sisters). Aunts and uncles have a 25% overlap with nieces and nephews, as do grandparents with grandchildren. First cousins share 12.5% of their genetic endowment. If genes are implicated in a trait, people who are more closely related should be more likely to share it. 107. Discuss some of the causes of infertility in men. ANSWER: Answers will vary. A low sperm count—or lack of sperm—is the most common infertility problem in men. Men’s fertility problems have a variety of causes: genetic factors, environmental poisons, diabetes, sexually transmitted infections (STIs), overheating of the testes (which happens now and then among athletes, such as long-distance runners), pressure (as from using narrow bicycle seats), aging, certain prescription and illicit drugs, and obesity (American Fertility Association, 2014). Sometimes the sperm count is adequate, but other factors such as prostate or hormonal problems deform sperm or deprive them of their motility. Motility can also be impaired by the scar tissue from infections, such as STIs. 108. How does endometriosis result in infertility? ANSWER: Answers will vary. Endometriosis is the inflammation of endometrial tissue sloughed off into the abdominal cavity rather than out of the body during menstruation; the condition is characterized by abdominal pain and sometimes infertility. Endometriosis can obstruct the fallopian tubes, where conception normally takes place. Endometriosis has become fairly common among women who delay childbearing. Each month, tissue develops to line the uterus in case the woman conceives. This tissue—the endometrium—is then sloughed off during menstruation. But some of it backs up into the abdomen through the fallopian tubes. It then collects in the abdomen, where it can cause abdominal pain and lessen the chances of conception. Physicians may treat endometriosis with hormones that temporarily prevent menstruation or through surgery. 109. Discuss the types of teratogens. ANSWER: Answers will vary. Teratogens are environmental agents that can harm the embryo or fetus. They include drugs taken by the mother, such as marijuana and alcohol, and substances that the mother’s body produces, such as Rh-positive antibodies. Another class of teratogens is the heavy metals, such as lead and mercury, which are toxic to the embryo. Hormones are healthful in countless ways—for example, they help maintain Copyright Cengage Learning. Powered by Cognero. Page 17 Name: Class: Date: Chapter 2 – Heredity and Prenatal Development pregnancy—but excessive quantities are harmful to the embryo. Exposure to radiation can also harm the embryo. Finally, disease-causing organisms—also called pathogens—such as bacteria and viruses are also teratogens. 110. Discuss the cause and effects of preeclampsia. ANSWER: Answers will vary. Preeclampsia (also called toxemia) is a life-threatening disease characterized by high blood pressure that may afflict women late in the second or early in the third trimester. Women with toxemia often have premature or undersized babies. Toxemia also causes some 15% to 20% of pregnancy-related maternal deaths. Preeclampsia appears to be linked to malnutrition, but the causes are unclear. Women who do not receive prenatal care are much more likely to die from preeclampsia than those who do receive prenatal care. 111. Discuss the effects of Rh incompatibility on a fetus. ANSWER: Answers will vary. Rh incompatibility does not affect a first child because women will not have formed Rh antibodies. The chances of an exchange of blood are greatest during childbirth. If an exchange occurs, the mother produces Rh-positive antibodies to the baby’s Rh-positive blood. These antibodies can enter the fetal bloodstream during subsequent deliveries, causing anemia, mental deficiency, or death. 112. Discuss the effects of thalidomide on pregnant women. ANSWER: Answers will vary. Thalidomide was marketed in the 1960s as a treatment for insomnia and nausea and provides a dramatic example of critical periods of vulnerability to teratogens. A fetus’s extremities undergo rapid development during the second month of pregnancy. Thalidomide taken during this period almost invariably causes birth defects, such as missing or stunted limbs. The drug is no longer prescribed for pregnant women. 113. Discuss the cause of fetal alcohol syndrome (FAS). ANSWER: Answers will vary. Alcohol passes through the placenta, and drinking by a pregnant woman poses risks for the embryo and fetus. Heavy drinking can be lethal and is also connected with deficiencies and deformities in growth. Some children of heavy drinkers develop fetal alcohol syndrome (FAS) (Connor et al., 2006; see Figure 2.12 Figure 2.12). Babies with FAS are often smaller than normal, and so are their brains. They have distinct facial features: widely spaced eyes, an underdeveloped upper jaw, and a flattened nose. Psychological characteristics appear to reflect dysfunction of the brain. 114. How does the amniotic sac protect the embryo and fetus? ANSWER: Answers will vary. The embryo and fetus develop within a protective amniotic sac in the uterus. This sac is surrounded by a clear membrane and contains amniotic fluid. The fluid serves as a kind of natural air bag or shock absorber, allowing the embryo and fetus to move around without injury. It also helps maintain an even temperature. 115. Discuss the role played by a parent’s age in relation to prenatal development. ANSWER: Answers will vary. Older fathers are more likely to produce abnormal sperm. The mother’s age also matters. From a biological vantage point, the 20s may be the ideal age for women to bear children. Teenage mothers have a higher incidence of infant mortality and children with low birth weight. Girls who become pregnant in their early teens may place a burden on bodies that may not have adequately matured to facilitate pregnancy and childbirth. Women’s fertility declines gradually until the mid-30s, after which it declines more rapidly. Women possess all their ova in immature form at birth. Older fathers are more likely to produce abnormal sperm, leading to fertility problems. Copyright Cengage Learning. Powered by Cognero. Page 18