Neural Development and Processes Answer Key From 75 to 119

Name : Clas s: Dat e: Chapter 04 75. A strand of DNA serves as a template (model) for the synthesis of ____. a. chromosomes b. RNA c. Proteins d. carbohydrate s ANSWER: b 76. Enzymes serve as ____. a. genetic templates b. physiological markers of chemical reactions in the body c. biological catalysts that regulate chemical reactions in the body d. catalysts for the synthesis of protein molecules ANSWER: c 77. Chemically, what is the route from genes to their expression? a. DNA to proteins to RNA b. DNA to RNA to proteins c. Proteins to DNA to RNA d. RNA to DNA to proteins ANSWER: b 78. A person with two recessive genes is considered to be ____ for that trait. a. homozygous b. heterozygous c. unitary d. marginal ANSWER: a 79. Suppose “A” is a dominant gene for the ability to taste phenylthiocarbamide (PTC) and “a” is a recessive gene for the inability to taste it. Which couples could possibly have both a child who tastes it and a child who does not? a. father AA, mother aa b. father Aa, mother AA c. father Aa, mother Aa d. father AA, mother AA ANSWER: c 80. A trait not expressed when combined with a dominant trait is called a(n) ____ trait. a. nurture Name : Clas s: Dat e: Chapter 04 b. recessive c. dominant d. homozygou s ANSWER: b 81. Suppose that adopted children are more similar to their biological parents than their adoptive parents in their preferences for a flavor of ice cream. Which statement is true in this circumstance? a. Heritability of this trait is high. b. Preferences for ice cream are determined solely by the environment. c. Flavors of ice cream are naturally selected. d. Heritability of this trait is low. ANSWER: a 82. An autosomal gene is a gene ____. a. on the X chromosome b. on the Y chromosome c. on any chromosome other than the X or Y chromosome d. that shows no evidence of crossing over ANSWER: c 83. Which pair of sex chromosomes is found in a normal male mammal? a. XX b. XY c. YY d. YZ ANSWER: b 84. In general, biologists who speak of sex-linked genes are typically referring to genes on ____. a. autosomal chromosomes b. more than one chromosome c. the X chromosome d. the Y chromosome ANSWER: c 85. An example of a sex-linked trait is ____. a. green eye color b. red-green color vision deficiency c. temperament Name : Clas s: Dat e: Chapter 04 d. intelligence ANSWER: b 86. Sex-limited genes are found on ____. a. X chromosomes only b. Y chromosomes only c. X and Y chromosomes d. any autosomal chromosomes ANSWER: d 87. A gene is found that controls the age at which a man grows bald, if at all. That gene seldom affects women, even if they have the gene. What kind of gene is this MOST likely to be? a. An X-linked gene b. A sex-limited gene c. A sex-linked dominant gene d. A sex-linked recessive gene ANSWER: b 88. Which statement best explains why males can grow breasts under certain hormonal conditions? a. Sex-linked genes become activated. b. The Y chromosome becomes activated. c. Sex-limited genes become activated. d. Breast growth is linked to color vision deficiency. ANSWER: c 89. On a given trait, high heritability suggests that ____. a. adopted children will closely resemble their biological parents b. adopted children will closely resemble their adoptive parents c. identical twins will be less similar to each other than adopted siblings d. fraternal twins will be more similar to each other than identical twins ANSWER: a 90. Any estimate of the heritability of a particular trait is specific to ____. a. a given population b. the parents c. the trait d. the strength of the trait ANSWER: a Name : Clas s: Dat e: Chapter 04 91. Individuals afflicted with PKU need to avoid ____. a. foods high in phenylalanine b. foods high in vitamin K c. alcohol d. sunlight ANSWER: a 92. Why do children with PKU develop intellectual disabilities? a. Unmetabolized amino acids accumulate and affect the brain. b. Essential axons lack myelin sheaths. c. Dendrites and synapses fail to form in associative areas of the cortex. d. Their immune systems do not fight off brain infections. ANSWER: a 93. How is it possible to prevent the intellectual disabilities that are generally associated with PKU? a. Through exercise b. Through diet c. Through drugs d. Through exposure to bright light ANSWER: b 94. Changes in single genes are called ____. a. alterations b. mutations c. mendelians d. enzymes ANSWER: b 95. For natural selection to generate evolutionary change in a population ____. a. there need not be any differences in the traits of individuals in that population b. the change in gene frequencies must help the species in the long run c. the differences must have a hereditary basis d. the change in gene frequencies will probably be harmful to the species ANSWER: c 96. Which statement is true with respect to evolution? a. “If you don’t use it, you lose it.” Name : Clas s: Dat e: Chapter 04 b. Evolutionary success is assessed by the number of one’s offspring surviving to reproduce. c. Evolution benefits the species, in the long run. d. Evolution benefits the individual. ANSWER: b 97. Breeding some animals selectively because they possess some desirable characteristic is called ____. a. evolution b. natural selection c. artificial selection d. artificial insemination ANSWER: c 98. Which of the following represents Lamarckian evolution? a. “Survival of the fittest” b. “Reproduction of the fittest” c. “If you don’t use it, you lose it” d. “Look out for number one” ANSWER: c 99. Evolution improves the fitness of the population, which is evolutionarily defined as ____. a. the number of copies of one’s genes that endure in later generations b. survival of the individual c. ability to adapt to a variety of environments d. overall health and well-being ANSWER: a 100. An evolutionary psychologist would likely be most interested in studying ____. a. altruistic behavior of meerkats b. cardiovascular function across species c. anatomy of the rat brain d. neurotransmitters in primates ANSWER: a 101. What is true about altruistic behavior? a. It is evident in every animal species. b. It can be completely explained in terms of genetic contributions. c. It is difficult to explain from an evolutionary/genetic point of view. d. It has a genetic component only in humans. Name : Clas s: Dat e: Chapter 04 ANSWER: c 102. Why is a genetic explanation for altruism problematic? a. Only non-human animals exhibit altruistic behaviors. b. Altruistic behaviors rarely benefit the individual performing them. c. Altruism is more common among the young than among adults. d. No behavior has been linked to any genes. ANSWER: b 103. Which action best illustrates altruistic behavior? a. Bullying other kids in the lunch line b. Spreading rumors about your boss c. Picking up your room d. Helping an elderly person across the street ANSWER: d 104. Organisms that help those they recognize as capable of returning the favor are displaying ____. a. kin selection b. group selection c. reciprocal altruism d. sociobiology ANSWER: c 105. Kin selection as an explanation for altruistic behavior would argue that ____. a. individuals help others who help them b. individuals pick their mates based on how altruistic they are c. individuals spread their genes by helping their relatives d. society benefits as a whole when individuals help each other ANSWER: c 106. Group selection as an explanation for altruistic behavior would argue that ____. a. individuals are more likely to reproduce when stress is low b. individuals pick their groups based on how altruistic they are c. cooperative groups thrive better than do uncooperative groups d. society benefits as a whole when individuals help each other ANSWER: c 107. Group selection works well as an explanation for human behavior because humans ____. Name : Clas s: Dat e: Chapter 04 a. can expel uncooperative individuals from groups b. are a highly social species who emphasize groups c. can make rational choices about mate selection d. benefit from living in groups ANSWER: a 108. Humans may have been able to evolve such big brains without sacrificing other functions because of ____. a. exercise b. mutations c. deletions d. diet ANSWER: d 109. Proteins called ____ bind DNA into a shape that is more like string wound around a ball. a. enzymes b. histones c. esters d. acetyl groups ANSWER: b 110. The field of epigenetics deals with how ____. a. reproductive fitness can be altered b. spontaneous mutations occur c. genes determine behavior d. experiences can turn genes on or off ANSWER: d 111. Removal of ____ turns genes off. a. enzymes b. histones c. esters d. acetyl groups ANSWER: d 112. At later stages of the neuron’s development, neurotrophins ____. a. increase the branching of axons b. cause the neuron’s death c. become converted into myelin Name : Clas s: Dat e: Chapter 04 d. connect the axon to axons of adjoining cells ANSWER: a 113. Which statement most accurately describes embryonic development of the nervous system in humans? a. The majority of cells remain as primitive neurons until birth. b. All synapses that are formed are permanent. c. Neurons form before birth; synapses form after birth. d. Far more neurons are produced than will ultimately survive. ANSWER: d 114. Why is it that all neurons in a healthy adult brain have made appropriate connections? a. Chemical messages from our muscles tell our brain how many neurons to form. b. If an axon does not make the appropriate connections by a certain age, it dies. c. We are born with all connections formed. d. Connections form rapidly, but we learn to use whatever connections have formed. ANSWER: b 115. Define proliferation during neural development. ANSWERProliferation involves the production of new cells. Early in development, the cells lining the ventricles of the brain divide. Some cells remain where they are, continuing : to divide. Others become primitive neurons and glia that begin migrating to other locations. 116. Describe how phantom limb sensations that seemingly come from a missing hand might occur when the face is touched. ANSWERThe area of the cortex that normally responds to the face can send collateral sprouts to the adjacent area of the cortex that was innervated by the hand. Investigators recorded : from the cerebral cortices of monkeys whose sensory nerves from one forelimb had been cut 12 years previously. They found that the stretch of cortex previously responsive to the limb was now responsive to the face (Pons et al., 1991). After loss of sensory input from the forelimb, the axons representing the forelimb degenerated, leaving vacant synaptic sites at several levels of the CNS. Evidently, axons representing the face sprouted into those sites in the spinal cord, brain stem, and thalamus (Florence & Kaas, 1995; Jones & Pons, 1998). Or perhaps axons from the face were already present but became stronger through denervation supersensitivity. Brain scan studies confirm that the same processes occur with humans. Later studies showed that this process can be much quicker than 12 years 117. Describe Lamarckian evolution and the evidence for or against it. ANSWERYou may have heard people say something like, “Because we hardly ever use our little toes, they get smaller and smaller in each succeeding generation.” This idea is a : carryover of biologist Jean- Baptiste Lamarck’s theory of evolution through the inheritance of acquired characteristics, known as Lamarckian evolution. According to Name : Clas s: Chapter 04 this idea, if you exercise your arm muscles, your children will be born with bigger arm muscles, and if you fail to use your little toes, your children’s little toes will be smaller than yours. However, biologists have found no mechanism for Lamarckian evolution to occur and no evidence that it does. Using or failing to use some body structure does not change the genes. People’s little toes will shrink in future generations only if people with genes for smaller little toes manage to reproduce more than other people do. 118. How is brain development related to adolescent impulsivity? ANSWERAdolescents are widely regarded as impulsive and prone to seek immediate pleasure, as compared to adults. Impulsiveness is a problem if it leads to risky driving, drinking, : sex, spending sprees, and so forth. Many studies have found that adolescent humans show stronger brain responses than older adults do when anticipating rewards, and weaker responses in the areas of the prefrontal cortex responsible for inhibiting behaviors. That type of evidence influenced the U.S. Supreme Court to rule that adolescents are less responsible for their actions than adults are, because they are less able to restrain their impulses. However, although the prefrontal cortex is indeed less mature in adolescents, its immaturity is at best only part of the explanation for impulsivity. Adolescents are not incapable of restraining their impulses, and in many laboratory tests they inhibit impulses just as well as adults. The heightened impulsivity occurs almost entirely in social situations when adolescents are trying to impress their peers. Adolescents are highly responsive to social support and social influence. 119. Describe the relationship between heredity and environment. ANSWERSuppose someone asks whether singing ability depends on heredity or environment. That question as stated is meaningless. Unless you had both heredity and environment, : you couldn’t sing at all. However, we can rephrase the question meaningfully: Do the observed differences among individuals depend more on differences in heredity or differences in environment? For example, if you sin better than someone else, the reason could be different genes, better training, or both. If the variations in some characteristic depend largely on genetic differences, the characteristic has high heritability. To determine the heritability of any characteristic, researchers rely mainly on three kinds of evidence. First, they compare monozygotic (“from one egg”) twins and dizygotic (“from two eggs”) twins. People usually call monozygotic twins “identical” twins, but that term is misleading, because identical twins often differ in important ways. Some are mirror images of each other. Also, for epigenetic reasons, certain genes may be activated more in one twin than the other. Still, they have the same genes, whereas dizygotic twins do not. A stronger resemblance between monozygotic than dizygotic twins suggests a genetic contribution. However, it is not totally decisive, because people who look alike tend to be treated alike. A second kind of evidence is studies of adopted children. Any tendency for adopted children to resemble their biological parents suggests a hereditary influence. However, again the evidence is not always decisive. The biological mother contributes not only her genes, but also the prenatal environment. A mother’s health, diet, and smoking and drinking habits during pregnancy can greatly influence her child’s development, especially the brain development. A similarity between an adopted child and the genetic mother could reflect both genetic influences and prenatal environment. A third type of evidence is to identify specific genes linked to some behavior. In some cases, researchers test a hypothesis, such as “a gene that decreases the activity of the serotonin transporter may be linked to an increased risk of depression.” In other Dat e: Name : Clas s: Chapter 04 cases, they examine all the genes of people with some condition (such as depression or schizophrenia), looking for any gene that is more common than in the rest of the population. However, this procedure tests thousands of hypotheses at once (one for each gene), and risks reporting a false association. Even a trait with high heritability can be modified by environ- mental interventions. A prime example is phenylketonuria, or PKU, a genetic in- ability to metabolize the amino acid phenylalanine. If PKU is not treated, phenylalanine accumulates to toxic levels, impairing brain development and leaving a child mentally retarded, restless, and irritable. Approximately one percent of Europeans carry a recessive gene for PKU. Fewer Asians and almost no Africans have the gene. Although PKU is a hereditary condition, environmental interventions can modify it. Physicians in many countries routinely test the level of phenylalanine or its metabolites in babies’ blood or urine. If a baby has high levels, indicating PKU, physicians advise the parents to put the baby on a strict low-phenylalanine diet to protect the brain. The success of this diet shows that heritable does not mean unmodifiable. Dat e: