This Document Contains Chapters 24 to 26 Chapter 24 Human Biology: Materials Exchange and Control Contents Homeostasis Exchanging Materials: Basic Principles Transporting Materials: The Circulatory System The Nature of Blood The Heart Arteries, Veins, and Capillaries Skin: The Body’s Container Primary Functions of the Skin The Structure of the Skin Other Features of the Skin Exchanging Gases: The Respiratory System Structure and Function of Lungs The Mechanism of Breathing Homeostasis and Breathing A Closer Look: Cigarette Smoking and Your Health Obtaining Nutrients: The Digestive System Processing Food Nutrient Uptake Nutrition Kinds of Nutrients A Closer Look: Body Mass Index Guidelines for Obtaining Adequate Nutrients Your Health and Body Weight A Closer Look: The Dynamic Skeleton A Closer Look: Exercise: More than Just Maintaining Your Weight Waste Disposal: The Excretory System Control Mechanisms The Structure of the Nervous System The Nature of the Nerve Impulse Activities at the Synapse Endocrine System Function Sensory Input Chemical Detection Light Detection Sound Detection Touch Output Mechanisms Muscles A Closer Look: Which Type of Exercise Do You Do? Glands Growth Responses Overview This chapter begins with a survey of four systems of the body—the circulatory, respiratory, digestive, and excretory systems. These four systems are involved in the exchange of materials across membranes. This exchange is limited by the amount of surface area present. All of these systems have special mechanisms to provide large surface areas that allow for necessary exchanges. The circulatory system consists of a pump, the heart, and blood vessels that distribute the blood to all parts of the body. The blood is a carrier fluid that transports molecules and heat. The exchange of materials between the blood and body cells takes place through the walls of the capillaries. The contraction of arterioles can regulate the flow of blood, so blood can be sent to different parts of the body at different times. Hemoglobin in red blood cells is very important in the transport of oxygen. The respiratory system consists of the lungs and associated tubes that allow air to enter and leave the lungs. The diaphragm and muscles of the chest wall are important in facilitating breathing. In the lungs tiny sacs called alveoli provide a large surface area in association with capillaries, which allows for rapid exchange of oxygen and carbon dioxide. The digestive system is involved in disassembling food molecules. This involves several processes: grinding by the teeth and stomach, emulsification of fats by bile from the liver, addition of water to dissolve molecules, and the action of enzymes that break complex molecules into simpler molecules for absorption. The intestine provides a large surface area for the absorption of nutrients because it is long and contains many tiny projections of the wall that increase surface area. Once absorbed, the materials travel to the liver, which modifies molecules. Nutrition involves an understanding of the kinds of molecules that are nutrients and how they are used in the body. There are several kinds of guidelines available to help people obtain the correct nutrients in appropriate amounts. Being overweight, obese, and underweight are common problems associated with poor nutritional habits and can adversely affect a person’s health, quality of life, and life span. The excretory system is a filtering system of the body. The kidneys consist of nephrons into which the circulatory system filters fluid. Most of this fluid is useful and is reclaimed by the cells that make up the walls of these tubules. Materials that are present in excess and those that are harmful escape. Some molecules may be secreted into the tubule, as well, before being eliminated from the body. The final section compares the control functions of the nervous and endocrine systems, the kinds of effects they have, and their characteristics. The nerve impulse is the result of sodium ions entering the cell as a result of a change in the permeability of the cell membrane. Thus, a wave of depolarization passes down the length of a neuron to the synapse. The axon of a neuron secretes a neurotransmitter, such as acetylcholine, into the synapse, where these molecules bind to the dendrite of the next cell in the chain, resulting in an impulse in it as well. Cholinesterase present in the synapse destroys acetylcholine so that it does not repeatedly stimulate the dendrite. Several different kinds of sensory input are possible. Many kinds of chemicals can bind to cell surfaces and be recognized. This is probably how the sense of taste and smell function, although the details of how molecules are recognized are not fully understood. Light energy can be detected because light causes certain molecules in the retina of the eye to decompose and stimulate neurons. Sound can be detected because fluid in the cochlea of the ear is made to vibrate and special cells detect this movement and stimulate neurons. The sense of touch consists of a variety of different receptors that respond to pressure, cell damage, and temperature. The nervous and endocrine systems cause changes in the activities of muscles and glands. Skeletal muscle responds to nervous stimulation, resulting in movements of the skeleton. Smooth muscle and cardiac muscle have internally generated contractions that may be modified by nervous stimulation or hormones. Glands are present as two types, exocrine glands that secrete through ducts into the cavity of an organ or the surface of the skin, and endocrine glands that release their secretions into the circulatory system. Digestive glands and sweat glands are examples of exocrine glands. Endocrine glands such as the ovaries, testes, and pituitary gland change the activities of cells and are often responsible for responses that require growth over a period of time. It is becoming clear that the endocrine system and the nervous system are interrelated. Actions of the endocrine system can change how the nervous system functions, and the reverse is also true. Much of this interaction takes place in the brain-pituitary gland association. For Class Discussions 1. All of the following occur at the synapse between nerve cells except a. neurotransmitters are released. b. neurotransmitters are destroyed. c. enzymes are active. d. neurotransmitters flow both ways across the synapse. 2. The normal flow of blood through the heart would be a. right atriumright ventriclelungsleft atriumleft ventricle. b. right atriumleft atriumleft ventricleaorta. c. lungsright atriumright ventricleaorta. d. right atriumright ventricleaortaleft atriumleft ventriclelungs. 3. The normal flow of blood would be a. heartcapillaries arteriesveinsheart. b. heartarteriescapillariesveinsheart. c. heartveinscapillariesarteriesheart. d. heartveinsarteriescapillariesheart. 4. Sense organs send their information to a. endocrine glands and the central nervous system. b. the central nervous system. c. skeletal muscle. d. skeletal, cardiac, and smooth muscle. 5. Chewing is important because it a. alters the food chemically. b. adds enzymes that cause starch, proteins, and fats to break down. c. increases the surface area exposed to the action of enzymes. d. is required by your mother. 6. Gastric juice a. is very acidic. b. digests fats. c. assists the function of saliva. d. is produced by the pancreas. 7. Hormones are a. able to regulate growth. b. produced by exocrine glands. c. transported along the length of nerve cells. d. not controlled by the nervous system. 8. The breathing rate is controlled by a. the amount of oxygen in the blood. b. the pH of the blood. c. how fast the heart is beating. d. the number of capillaries present in the lungs. 9. In which of the following ways are the nervous and endocrine systems similar? a. Both contain cells that carry impulses. b. Both secrete molecules that attach to other cells. c. Both typically are fast acting. d. Both typically use the circulatory system to transport molecules. 10. Which of the following is true for the brain? a. All parts of the brain are the same in terms of the kinds of neurotransmitters. b. Several kinds of neurotransmitters are used to store information. c. Different parts of the brain are sensitive to different neurotransmitters. d. Neurotransmitters are distributed to various parts of the brain. Answers: 1d, 2a, 3b, 4b, 5c, 6a, 7a, 8b, 9b, 10c Answers to Questions for Thought 1. The primary functions of the heart and blood vessels are as follows. The heart is a pump that causes the blood to move. Arteries carry blood from the heart to the body. Veins carry blood from the body to the heart. Arterioles regulate how much blood flows to a part of the body. Capillaries are the site of exchange of molecules between the blood and cells of the body. The blood is the fluid that transports molecules from place to place. 2. The digestive system increases its ability to absorb nutrients by reducing the size of the molecules so that they can pass through the wall of the intestine easier, by having a large surface area across which the molecules can move, and by having large numbers of capillaries in the walls of the small intestine. 3. Breathing involves the cyclic contractions of the diaphragm and muscles of the chest wall. Their contraction increases the volume of the chest cavity, which causes a decrease in pressure and thus air flows into the lungs. The relaxation of these muscles causes the pressure inside the chest wall to increase and air is forced out of the lungs. 4. A chemical pump constantly transports sodium ions from the interior of the cell to the exterior. Therefore there are more sodium ions outside than inside and the cell and the cell membrane is polarized (there is a voltage difference between the inside and the outside of the cell). When a nerve cell is stimulated the permeability of the cell membrane is changed and sodium ions diffuse into the cell and that portion of the cell membrane is depolarized. When one portion of the cell membrane is depolarized it causes an adjacent section of the membrane to change its permeability and the impulse moves down the nerve cell. 5. Acetylcholine is a neurotransmitter. It is released at the end of the axon of one nerve cell and diffuses across the synapse where it attaches to receptor sites on the dendrites of the other nerve cell causing it to carry an impulse. 6. The nasal epithelium detects molecules. The taste buds detect molecules. The cochlea of the ear detects sound vibrations. The retina of the eye detects light. 7. The central nervous system consists of the brain and spinal cord and is resposible for integrating input from sense organs and generating messages that cause glands and muscles to act. The peripheral nervous system consists of nerve fibers that connect sense organs, muscles, and glands to the central nervous system. It is divided into two functional systems, the motor system that carries information from the central nervous system to muscles and glands and the sensory system that carries information from sense organs to the central nerous system. 8. When a nerve cell is stimulated, a small portion of the cell membrane depolarizes as Na+ flows into the cell through the membrane. This encourages the depolarization of an adjacent portion of the membrane, and it depolarizes a short time later. In this way a wave of depolarization passes down the length of the nerve cell. Shortly after a portion of the membrane is depolarized, the ionic balance is reestablished. It is repolarized and ready to be stimulated again. 9. Large, multicellular organisms need a circulatory system because organisms and their cells must exchange materials through their surfaces and most cells in large organisms are buried within the organism. The circulatory system serves to carry molecules to and from cells that are deep within the organism. 10. The five food groups are (1) grain products, which provide carbohydrate, fiber, several B vitamins and vitamin E, and the minerals iron and magnesium; (2) fruits, which provide carbohydrate, fiber, water, and vitamin C; (3) vegetables, which provide carbohydrate, fiber, several B vitamins and vitamins A, C, E, and K and the minerals iron and magnesium; (4) dairy products, which provide protein, carbohydrate, fat, several B vitamins and vitamins D and the mineral calcium; (5) meat, poultry, fish, and dry beans, which provide protein, fat, several B vitamins, and E vitamins from seeds and nuts, and the mineral iron. 11. The villi and the long length of the small intestine increase the surface area, which increases the ability of the intestine to absorb nutrients. 12. Smooth muscle is involuntary, slow to act, and is able to maintain a contraction for a long time without fatigue. Skeletal muscle is voluntary, quick to act, and unable to maintain a contraction for a long time without fatigue. 13. Answer will vary. One possible answer: when you run up a hill, your leg and arm muscles move in a coordinated way to provide power. They burn fuel (glucose) for energy and produce carbon dioxide and lactic acid as waste products, which tend to lower the ph of the blood. Your heart beats faster to provide oxygen and nutrients to the muscles, you breathe faster to supply the muscles with oxygen and get rid of carbon dioxide, and the blood vessels in the muscles dilate to allow more blood to flow to them. As you run, you generate excess heat. As a result, more blood flows to the skin to get rid of the heat and sweat glands begin to secrete, thus cooling the skin. 14. Plasma, cellular material, and platelets. 15. The larger, more powerful left side of your heart receives oxygenated blood from your lungs, delivers it through your aorta to all parts of your body, and returns it to your right atrium by way of large veins known as the superior vena cava and inferior vena cava. For Further Analysis 1. The primary technical problems would be the difficulty of making extremely thin- walled tubes that were permeable to some materials but not others. 2. The larger the surface area exposed the greater the amount of heat transfer possible. 3. The major nutrients missing from the diet would be calcium and since vitamin D is typically added to milk it may be in short supply as well. 4. Similarities - Both are communication systems. Both use the transfer of molecules to accomplish their function. Both involve actions that take place at the cellular level. Differences - Nervous responses are generally rapid, endocrine slow. Endocrine responses often involve growth, nervous does not. Nervous involves direct transfer of information from one cell to an adjacent cell. The endocrine system does not. 5. The lungs consist of many tiny sacs called alveoli. The small intestine is long and has many finger-like villi. The kidney contains millions of tubular nephrons. Chapter 25 Human Biology: Reproduction Contents Sexual Reproduction The Mechanics of Meiosis Human Sexuality from Different Points of View Chromosomal determination of Sex Male and Female Fetal Development Sexual Maturation of Young Adults The Maturation of Females The Maturation of Males Spermatogenesis Oogenesis Hormonal Control of Female Sexual Cycles Hormonal control of Fertility Fertilization, Pregnancy and Birth Twins Birth Contraception Chemical Methods Hormonal Control Methods Timing Method Barrier Methods Surgical Methods Abortion Changes in Sexual Function with Age Hormone Therapy Impotence A Closer Look: The Sexuality Spectrum A Closer Look: Karyotyping and Down Syndrome A Closer Look: Cryptorchidism—Hidden Testes A Closer Look: Sexually Transmitted Diseases Overview This chapter begins with the mechanics of the process of meiosis. Encourage students to put this process in perspective when they think about a generalized life cycle. It is important that they see the relationship of meiosis to mitosis as they cover this material. A summary table of meiosis (Table 25. 1) allows students to review a concise overview of this process. It highlights those aspects of meiosis that related to the mechanics of the process and features that result in gametic variety. Following this section is one that deals with chromosomes and sex determination providing information on the roles played by autosomes and the sex chromosomes. The next section provides us with the opportunity to examine the ways our sexuality influences us throughout life, starting with the effect of the sex-determining chromosomes before birth as they direct the formation of hormones that control the development of sex organs. With the start of puberty, renewed hormonal activity causes major structural and behavioral changes that influence us for the remainder of our lives. Since our sexuality is tied to reproduction, we consider the production of offspring next. Finally, we turn our attention to normal sexual activity in the aging individual. We have tried to include a discussion of many of the areas of concern for young people based on the questions we receive. As far as possible, we have attempted to place the emphasis on biological rather than sociological discussion. A dissection laboratory experience might be appropriate with this chapter. Such dissections will emphasize the anatomical structures of the reproductive system in various animals. Boxed materials that illustrate the importance of sexual reproduction of the depth of our knowledge include: the concepts that explain the meiotic reasons why individuals differ, karyotyping and Down syndrome, and the human genome project. For Class Discussions 1. Fertilization of the human egg normally occurs after the a. lining of the uterus is thicker and filled with blood. b. egg has started development in the follicle. c. menstrual flow (or period) has started. d. egg has imbedded itself in the wall of the uterus. 2. The time of menstrual flow, or period, in a normal human female occurs a. at the same time as the egg is released from the ovary. b. approximately two days before the egg is released from the ovary. c. approximately two days after the egg is released from the ovary. d. approximately two weeks after the egg is released from the ovary. 3. Which is not one of the five factors that influence genetic diversity in offspring? a. mutations b. crossing-over c. segregation d. hormone cycles 4. If a female is under 15 years of age or has had three or more pregnancies in a two-year period which is not true? a. nutritional stores are inadequate to support a successful pregnancy b. the use of ‘street’ drugs ex. alcohol, can result in decreased nutrient exchange between the mother and fetus c. heavy smoking can result in low birth weights d. she will most likely have twins 5. Without this gene, the embryo would become female. a. SRY b. TDF c. X d. Turner’s 6. An individual who has XXY chromosomes has the genetic condition is known as a. Klinefelter’s syndrome b. Turner’s syndrome c. Barr’s syndrome d. Cryptorchidism 7. At puberty the hypothalamus begins to release a hormone known as gonadotropin-releasing hormone (GnRH), which stimulates the pituitary to release the hormones a. luteinizing hormone (LH) and follicle-stimulating hormone (FSH) b. oxytocin and follicle-stimulating hormone (FSH) c. estrogens and androgens d. testosterones and estrogens 8. Semen, or seminal fluid, is a mixture of sperm and secretions from three accessory glands. Which is not an accessory gland? a. seminal vesicles b. prostate c. bulbo-urethral gland d. pituitary 9. Men must be able to release at least ____?___ sperm per milliliter to be fertile? a. 400,000 b. 100 million c. 400 million d. one each month 10. The follicle from which the oocyte erupted develops into a gland like structure called the a. corpus luteum b. seminal vesicle c. polar body d. epididymis 11. The lining of the uterus, the ___?___, is shed during menstruation, menstrual flow, or a period. a. epidermis b. endometrium c. epididymis d. hypothalamus 12. Which of the following is not a vitamin? a. Thiamine b. Riboflavin c. Niacin d. Calcium 13. In most women, a secondary oocyte is released from the ovary about ___?___ days before the next menstrual period. a. 2 b. 7 c. 14 d. 21 14. If a woman normally has a regular 21-day menstrual cycle, ovulation would occur about day ___?___ in the cycle. a. 7 b. 14 c. 21 d. 31 15. This division of embryonic cells is called a. meiosis b. mitosis c. cleavage d. both b and c above 16. Two other membranes, the chorion and allantois, fuse with the lining of the uterus to form the structure known as the a. placenta b. yolk sac c. digestive system d. spinal cord 17. If during cleavage the embryo splits into two separate groups of cells, the result will be a. Siamese twins b. identical twins c. fraternal twins d. twins of different sexes Answers: 1a, 2d, 3d, 4d, 5a, 6a, 7a, 8d, 9b, 10a, 11b, 12d, 13c, 14b, 15d, 16b. 17. b. Answers to Questions for Thought 1. Haploid cells do not have homologous chromosomes; diploid cells do. 2. Homologous chromosomes line up in pairs, not as individuals. 3. 4. Rhythm method of conception control 5. Have students check their illustrations in comparison to those in the text. 6. HRT stands for hormone replacement therapy. It may be used by women to augment the natural production of the hormones estrogen and progestin. HRT might have long-term benefits for women with osteoporosis and heart disease, but that it might increase the risk for breast cancer. 7. 8. 9. 10. Ovulation and menstruation are two hormonally controlled cycles of the female reproductive system. The hormones regulate the ovulation cycle so that the ovary releases the egg on or about the fourteenth day of the cycle. At this point the lining of the uterus is thick and is prepared to accept a fertilized egg for implantation. If no such zygote is present, the lining of the uterus is sloughed off in the process called menses or flow. The building and sloughing off of the uterine wall is called the menstrual cycle. 11. Fraternal twins are derived from the fertilization of two separate eggs by two different sperm. Identical twins are derived from a single fertilized egg that has begun to undergo cleavage and then separated into two different cell masses. Each of these masses then develops into an individual. 12. Causes of infertility 13. Answer will vary. One possible response: An organism with two sets of chromosomes can produce many combinations of chromosomes when it produces sex cells leading to greater genetic diversity in subsequent generations. 14. Point mutations and chromosomal aberrations. In point mutations, a change in a DNA nucleotide results in the production of a different protein. In chromosomal aberrations, genes are rearranged when parts of chromosomes are duplicated, deleted, or inverted. By causing the production of different proteins, both types of mutations increase diversity. 15. During meiosis I, the number of chromosomes is reduced from the diploid number to the haploid number. Therefore, it is often referred to as a reduction division. Invitation To Inquiry 1. From a cultural standpoint, the answer is no. This has been understood since Margaret Mead's work in the 1920s. While males and females may develop the appropriate genitals, the sexuality of an individual will be greatly influenced by the cultural mores in which they are immersed. 2. This answer will vary depending on the cultures studied. 3. This answer will vary depending on the cultures studied. 4. This answer will vary depending on the cultures studied. Generally the answer will be no. 5. This answer will vary depending on the cultures studied. 6. This answer will vary depending on the cultures studied. For Further Analysis 1. Depending on the concentration of the drug in the environment and the susceptibility of the individual, the hormone could have an effect such as increased or decreased fertility. 2. Acceptable levels of contaminating drugs could be determined by collecting data of the long term changes in fertility in the population. Base levels could also be determined using previously measured fertility data. 3. Lowering contaminating levels would require mass education to have unused medications returned to pharmacies for proper disposal, possibly lowering the amount of hormone used by the public, and the incorporation of special water treatment methods to ensure the destruction of contaminating drugs. Chapter 26 Mendelian and Molecular Genetics Contents Part I: Mendelian Genetics Updated Genetics, Meiosis, and Cells Single-Gene Inheritance Patterns A Simple Model of Inheritance - Dominant and Recessive Alleles Mendel’s Laws of Heredity A Closer Look: Cystic Fibrosis—What’s It About? Steps in Solving Heredity Problems: Single-Factor Crosses A Closer Look: Blame That Trait on Your Mother! A Closer Look: Muscular Dystrophy and Genetics More Complex Models of Inheritance X-Linked Genes Multiple Alleles Polygenic Inheritance Pleiotropy Codominance Incomplete Dominance Environmental Influences on Gene Expression Epigenetics and Gene Expression Part II: The Molecular Basis of Genetics What Is a Gene and How Does It Work? The Structure of DNA and RNA DNA Replication DNA Transcription Translation or Protein Synthesis A Closer Look: Basic Steps of Translation A Closer Look: Stem Cells Alterations of DNA Using DNA to OUR Advantage Overview The first part of the chapter introduces the concepts of single-gene inheritance patterns and terminology that will be used in specific contexts later on in the chapter: alleles, genotype, phenotype, homologous chromosomes, heterozygous, dominant, recessive and codominant. The typical shorthand notation used in genetics is also introduced. The section ends with a consideration of alternative inheritance genetics including: lack of dominance, multiple alleles, polygenic inheritance, pleiotropy, sex-linked characteristics, and the influence of the environment on the expression of genes. We designed this chapter to introduce the student to a difficult subject. A great deal of effort, therefore, has gone into relating the concepts of protein synthesis, chemical codes of DNA, and the cell life cycle in a manner that will allow the student who is totally unfamiliar with such material to grasp the information. The biggest difficulty in attempting to compare these types of materials is that students may lose sight of how the concepts relate to the total metabolism of the cell. It would be valuable to link the cellular processes of mitosis and meiosis with DNA replication and protein synthesis as the mean by which a cell expresses a phenotype. For Class Discussions 1. In humans, the genes for blood type A and B show lack of dominance and both dominate O. Two type O people would be able to have a. 1 O: 1 A: 1 B: 1 AB type children. b. only O type children. c. 1 O: 1 A type children. d. only AB type children. 2. Which is a group of proteins resulting from protein synthesis? a. structural b. carrier c. enzymatic/hormonal d. All the above are categories 3. Which of the following represents the sex chromosomes in a typical human female? a. XY b. XXX c. XO d. XX 4. The Y chromosome is carried in the a. egg. b. egg or sperm. c. polar body. d. sperm. 5. If a sperm containing an X chromosome fertilizes an egg, the child will be a. a girl. b. a boy. c. twins, a boy and a girl. d. twin boys. 6. Which one of the following does not express one of Mendel’s laws? a. When two different alleles are present for a given trait, the expression of one will mask the expression of the other. b. Alleles separate during the formation of sex cells. c. During the formation of sex cells, members of one gene pair separate from one another independently of members of other gene pairs. d. Genes located on the same chromosome have a greater tendency of being inherited together than do genes located on different chromosomes. 7. Which best represents the central dogma? a. DNA (replication) DNA (transcription) RNA (translation) Proteins b. RNA (replication) RNA (transcription) RNA (translation) Proteins c. DNA (replication) DNA (transduction) RNA (transcription) Proteins d. Proteins (replication) DNA (transcription) RNA (translation) Proteins 8. If an individual has the genotype BbCc, how many different kinds of gametes can that individual produce? a. one b. two c. three d. four 9. A nucleotide is composed of the following molecules arranged in this order: a. three amino acids covalently bonded in a series. b. three fatty acids individually bonded to three different places on glycerol. c. a base bonded to a sugar bonded to a phosphate. d. mRNA bonded to tRNA bonded to an amino acid. 10. Which of the following best describes the structure of DNA? a. single helix b. protein coil c. double helix d. globular RNA 11. DNA is a. a single chain of nucleotides containing deoxyribose. b. mainly found in the cytoplasm. c. composed of amino acids. d. a coiled double chain of nucleotides. 12. In DNA replication, a. a new cover is made for the gene. b. a new gene is made for the cover. c. Both of these occur. d. None of these occur. 13. “Since every cell in this patient’s body has the same genetic pattern, it is likely that…” a. he acquired this pattern from one of his parents. b. he was exposed to mutagenic agents. c. his mother was the only source of the mutant gene. d. All the above are true. 14. The term “recombinant DNA technology” refers to a. deliberately moving genes from one type of cell into another so that the new cell synthesizes that specific gene product b. selective breeding c. ensuring that a specific gene will be replicated over-and-over d. synthesizing DNA from scratch Answers: 1b, 2d, 3d, 4d, 5a, 6d, 7a, 8d, 9c, 10c, 11d, 12c, 13a, 14a. Answers to Questions for Thought Part I 1. 2. AA aa or Aa Aa or Aa aa 3. a. 1/4 or 25% b. 2/3 or 67% 4. Since both parents do not display achondroplasia, it must be assumed that the child is the result of a new mutation in one of the parents. 5. a. (4) All the girls have the normal phenotype but are carriers. b. (6) All the boys are color- deficient. 6. 7. The alleles responsible for color are neither dominant nor recessive to one another, and both express themselves in the heterozygous individual. Part II 8. DNA—A polymer of nucleotides that serves a genetic information source. In prokaryotic cells, it is duplex DNA (double-stranded) and contains no permanently attached proteins. In eukaryotic cells, it is in strands with attached histone proteins. When tightly coiled, it is known as a chromosome. RNA—A polymer of nucleotides that form on the template surface of DNA by transcription. Three forms have been identified: mRNA, rRNA, and tRNA. 9. Protein synthesis = transcription + translation. DNA chemical code opens with the aide of an enzyme; individual mRNA nucleotide units base-pair with exposed DNA nucleotides; and an mRNA molecule forms a single strand using DNA as a template. mRNA leaves DNA, and DNA reforms as a double helix; mRNA moves from the nucleus into the cytoplasm where tRNA molecules carrying specific amino acids move to the ribosome and base-pair with mRNA codons. Aligned amino acids combine in a sequence determined by codons of mRNA into a specific protein. mRNA leaves the ribosome, and tRNA molecules leave the ribosome without amino acids. The completed protein leaves the ribosome. 10. Chromosomal mutation is a change in the gene arrangement in a cell that is usually the result of a break in the DNA. A point mutation is a change in the nitrogenous base sequence of a DNA molecule. Recombinant DNA is an altered form created in a laboratory by manipulating genes. 11. DNA replication involves the alignment of DNA nucleotides on both strands of the DNA molecule; RNA production involves the same process. RNA nucleotides are aligned, however, only on the sequence of nucleotides that serve as the chemical code for proteins. 12. DNA—CATAAAGCA; mRNA—GUAUUUCGU. 13. Amino acid sequence—alanine, phenylalanine, arginine. 14. The production of customized stem cell lines. In this application a somatic cell from a patient would be inserted into a human egg from which the nucleus has been removed. The egg would divide and generate stem cells. These cells could then be cultured and used for therapy. In this example the stem cells could be used to create pancreatic cells to treat a diabetic patient. 15. The enzyme DNA polymerase moves in opposite directions on each side down the length of DNA, attaching new DNA nucleotides into position during DNA replication. Relatively weak hydrogen bonds hold each in position (AT, GC), while the new nucleotide is bonded to its neighboring nucleotide more strongly with covalent bonds between the sugar and phosphate of the new backbone. Invitation To Inquiry 1. The “guardian of the genome,” or the tumor-suppressor gene. 2. Cell death that has a genetic basis and is not the result of injury. 3. Benzopyrene is a carcinogen, i.e., cancer causing agent. For decades cancer has been empirically (based on commonplace experiences) linked to the use of tobacco, but only recently have researchers showed a cause-and-effect relationship between the two. Studies of patients with lung cancer revealed that 60 percent exhibited mutations in a gene known as p53. This gene is responsible for the synthesis of a protein that keeps cells growing in a controlled fashion and, when necessary, causes cells to commit suicide, a process called apoptosis. To be more specific, one of the compounds in tobacco (benzo[a]pyrene) has the ability to attach and mutate three spots in this gene, the same spots where the p53 genes have been changed in lung cancer patients. Studies of this nature give strong scientific evidence that smoking causes lung cancer. 4. When p53 initiates apoptosis in cancer cells, the cell’s DNA is cut into pieces and the cytoplasm and nucleus shrink. This is followed by its engulfment by phagocytes. In this manner, cells that are potentially dangerous to the entire body (tumor cells) are killed before they cause serious harm. For Further Analysis 1. It is important to remember that Mendel’s work was introduced only a little over 100 years ago. But in that time, science has progressed from his most basic hypothesis to a level of understanding that has already enabled the control of some of our most notorious genetic abnormalities. List five such diseases. List the kinds of genetic medicine is proposed to help with each. Ans: Will vary. 2. What is the genetic bases of the following diseases and what are their symptoms? a. Kearns-Sayre syndrome Ans: mtDNA mutation; heart block and weakness; skeletal muscle weakness in the face, trunk and limbs; degeneration of retina. b. Leber’s hereditary optic neuropathy (LHON) Ans: mtDNA mutation; sudden loss of central vision due to optic nerve death in young adults; onset at about 20 years of age; both males and females may be affected. c. Myoclonic epilepsy and red ragged fibers (MERRF) Ans: mtDNA mutation; muscle weakness; deafness; epilepsy; progressive. 3. Polydactyly is the most common genetic abnormality of the human hand and is classified into three types. a. What are these types? Ans: Type I – extra soft tissue only; Type II – incompletely developed including some bone, tendon, and cartilage; Type III – completely developed with own bone (rare). b. Diagram how such phenotypes would arise beginning with a mutation in the DNA, following through the central dogma and ending with how this phenotype would be produced. Ans: Normal DNA → mutagen → change in DNA → transcription of mutant gene → altered mRNA → moves to ribosome for translation → amino acid sequence is misaligned as a result of error in mRNA → protein produced has changed sequence of amino acids in comparison to normal protein → protein does not function as normal protein, i.e., if an enzyme it might hasten a different kind of chemical reaction → different chemical reaction results in new phenotype. 4. It is known that the difference between the genomes of humans and chimpanzees is about 1.5%. If this there is only this small difference between what appears to be two strikingly different organisms, a. What percentage difference do you think exists among humans? Ans: Will vary. b. Based on this information, comment on the validity of separating humans of the world in to separate races. Ans: Will vary. Instructor Manual for Integrated Science Bill W. Tillery, Eldon D. Enger , Frederick C. Ross 9780073512259
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