Forming a New Life PDF

03/10/2024 1 2 3 4 1  03/10/2024 Fertilization At birth, a girl is believed to have about 2...

03/10/2024 1 2 3 4 1  03/10/2024 Fertilization At birth, a girl is believed to have about 2 million immature ova in her two ovaries, or conception, is the process by which each ovum in its own follicle, or small sac. sperm and ovum—the male and female In a sexually mature woman, ovulation— gametes, or sex cells—combine to create a rupture of a mature follicle in either ovary single cell called a zygote, which then and expulsion of its ovum—occurs about duplicates itself again and again by cell once every 28 days until menopause. The division to produce all the cells that make ovum is swept along through one of the up a baby. fallopian tubes by the cilia, tiny hair cells, toward the uterus, or womb. 5 6 Sperms are produced in the testicles Fertilization normally occurs while the (testes), or reproductive glands, of a ovum is passing through the fallopian mature male at a rate of several hundred tube. million a day and are ejaculated in the If fertilization does not occur, the ovum semen at sexual climax. and any sperm cells in the woman’s body Deposited in the vagina, they try to swim die. The sperm are absorbed by the through the cervix, the opening of the woman’s white blood cells, and the ovum uterus, and into the fallopian tubes, but passes through the uterus and exits only a tiny fraction make it that far. through the vagina. 7 8 2  03/10/2024 Assisted Reproductive Technology (ART) or conception through artificial means, provides couples having difficulty conceiving naturally with a means to augment their fertility. 9 10 Artificial Insemination In Vitro Fertilization (IVF) The sperm is injected into a woman’s a woman’s ova are surgically removed, vagina, cervix, or uterus fertilized in a laboratory dish, and implanted in the woman’s uterus. 11 12 3  03/10/2024 Dizygotic Twins or fraternal twins, are the result of two separate eggs being fertilized by two different sperm to form two unique individuals. 13 14 Monozygotic Twins Or identical twins They result from the cleaving of one fertilized egg and are generally genetically identical. They can still differ outwardly because people are the result of the interaction between genes and environmental influences. 15 16 4  03/10/2024 17 18 Deoxyribonucleic Acid (DNA) The double-helix structure of a DNA molecule resembles a long, spiraling ladder whose Called the “stuff” of heredity steps are made of pairs of It is the molecule that carries genetic chemical units called bases. information for the development and The bases— adenine (A), functioning of an organism. thymine (T), cytosine (C), and guanine (G)—are the “letters” of the genetic code, which cellular machinery “reads.” 19 20 5  03/10/2024 Chromosomes Chromosomes are coils of DNA that consist of smaller segments called genes, the functional units of heredity 21 22 Twenty-two pairs of our 23 pairs of chromosomes are autosomes, chromosomes that are not related to sexual expression. The twenty-third pair are sex chromosomes—one from the father and one from the mother—that govern the baby’s sex 23 24 6  03/10/2024 Alleles These are genes that can produce alternative expressions of a characteristic (such as the presence or absence of dimples). Alleles are alternate versions of the same gene. Every person receives one maternal and one paternal allele for any given trait. When both alleles are the same, the person is homozygous for the characteristic; when they are different, the person is heterozygous. 25 26 DOMINANCE INHERITANCE RECESSIVE INHERITANCE Polygenic Inheritance The dominant allele For the trait to be is always expressed, expressed in or shows up as a recessive the interaction of several genes. trait in that person. inheritance, the For example, there is not an “intelligence” The person will look person must have gene that determines whether or not you the same whether or not he or she is two recessive are smart. Rather, a large number of genes heterozygous or alleles, one from work in concert to determine your homozygous each parent. because the intellectual potential. recessive allele doesn’t show. 27 28 7  03/10/2024 If you have brown hair, that is part of your Multifactorial Transmission phenotype, the observable characteristics through which your genotype, or underlying genetic makeup, is expressed. A phenomenon that explains that environmental experience modifies the The phenotype is the product of the expression of the genotype for most traits. genotype and any relevant environmental influences. Multifactorial transmission illustrates the interaction of nature and nurture and how they affect outcomes. 29 30 Chromosomal Abnormalities Chromosomal abnormalities typically occur because of errors in cell division, resulting in an extra or missing chromosome. 31 32 8  03/10/2024 Down Syndrome moderate-to-severe intellectual disability Children with Down syndrome, like other the most common chromosomal children with abnormality disabilities, tend to benefit cognitively, The condition is also called trisomy-21 socially, and because it is characterized in more than 90 emotionally when provided with regular, percent of cases by an extra 21st intensive therapies chromosome. designed to help them achieve important skills. 33 34 Genetic Counseling Genetic counseling can help prospective parents assess their risk of bearing children with genetic or chromosomal defects. 35 36 9  03/10/2024 37 38 One approach to the study of heredity Behavioral geneticists have developed a and environment is quantitative: It seeks means of estimating how much of a trait to measure how much heredity and is due to genetics and how much is the environment influence particular traits. result of environmental influences by This is the traditional goal of the science using a concept known as heritability. of behavioral genetics. 39 40 10  03/10/2024 Every trait is a consequence of genes and environment. By looking at groups of people with known genetic relationships and assessing whether or not they are concordant, or the same, on a given trait, behavioral geneticists can estimate the relative influence of genes and environment. 41 42 Reaction Range Canalization Reaction range refers to a range of The metaphor of canalization illustrates how heredity restricts the range of development for potential expressions of a hereditary trait. some traits. Body size, for example, depends largely on Highly canalized traits, such as eye color, are analogous to the deep canals. They are strongly biological processes, which are genetically programmed by genes, and there is little regulated. Tall people have tall children, opportunity for variance in their expression. Because of the deep, genetically dug channel, it and short people have short children. Even would take an extreme change in environment to so, a range of sizes is possible. alter their course. The canal is too deep for the water to easily slosh over. 43 44 11  03/10/2024 Genotype-Environment Interaction Genotype-Environment Correlation It usually refers to the effects of similar The environment often reflects or environmental conditions on genetically reinforces genetic differences. different individuals, and a discussion of This tendency is called genotype- these interactions is a way to environment correlation, and it works in conceptualize and talk about the different three ways to strengthen the phenotypic ways nature and nurture interact. expression of a genotypic tendency 45 46 1. Passive correlations 2. Reactive, or evocative, correlations You not only inherit genes from your Children with differing genetic makeups biological parents, you also inherit evoke different reactions from others. environments. Passive correlations are most applicable to This type of correlation is called reactive young children, whose parents have a great because the other people react to the deal of control over their early experiences. In child’s genetic makeup. addition, passive correlations function only when a child is living with a biologically related parent. 47 48 12  03/10/2024 3. Active correlations Nonshared Environmental Influences As children get older and have more freedom Although two children in the same family may bear to choose their own activities and a striking physical resemblance, siblings can differ environments, they actively select or create greatly in intellect and especially in personality. experiences consistent with their genetic One reason may be genetic differences, which tendencies. lead children to need different kinds of stimulation This tendency to seek out environments or to respond differently to a similar home compatible with one’s genotype is called environment. niche-picking; it helps explain why identical In addition, studies in behavioral genetics suggest twins reared apart tend to have similar that many of the experiences that strongly affect characteristics. development vary for different children in a family. 49 50 Nonshared Environmental Influences These nonshared environmental effects result from the unique environment in which each child in a family grows up. Children in a family have a shared environment—the home they live in, the people in it, and the activities family members jointly engage in—but they also, even if they are twins, have experiences that are not shared by their brothers and sisters. 51 52 13  03/10/2024 1. Physical health Obesity – Obesity is usually measured by body mass index, or BMI (comparison of weight to The risk of developing a wide variety of height), and is a risk factor for many negative medical disorders, including high blood health outcomes. pressure, heart disease, stroke, – The risk of obesity is 2 to 3 times higher for a rheumatoid arthritis, and epilepsy, has child with a family history of obesity. been found to be influenced by genetics. Therefore, we might reasonably conclude Life span, too, seems to be influenced by that obesity involves genetic contributions. genes. 53 54 2. Intelligence Indirect evidence of the role of heredity in intelligence comes from adoption and twin studies. Adopted children’s scores on Heredity exerts a strong influence on standardized intelligence tests are general intelligence, as measured by consistently closer to the scores of their intelligence tests, and a moderate effect biological mothers than to those of their on specific abilities such as memory, verbal adoptive parents and siblings; ability, and spatial ability. monozygotic twins are more alike in intelligence than dizygotic twins. 55 56 14  03/10/2024 3. Temperament and Personality Temperament underlies adult personality. Given the genetic contributions found for Psychologists call babies’ unique and temperament, one would predict characteristic ways of approaching and personality research should also illustrate reacting to environmental stimuli hereditary influences. temperament. Temperament is largely inborn and is relatively consistent over the years, although it may respond to special experiences or parental handling 57 58 4. Psychopathology There is evidence for a hereditary influence on such mental disorders as schizophrenia, autism, alcoholism, and the scientific study of mental disorders, depression. including their theoretical underpinnings, All tend to run in families and to show etiology, progression, symptomatology, greater concordance between diagnosis, and treatment. monozygotic twins than between dizygotic twins. However, heredity alone does not produce such disorders; an inherited tendency can be triggered by environmental factors. 59 60 15  03/10/2024 Schizophrenia is a neurological disorder characterized by loss of contact with reality; hallucinations and delusions; loss of coherent, logical thought; and inappropriate emotionality. Estimates of heritability range from 60 to 80 percent. 61 62 63 64 16  03/10/2024 During gestation, the period between conception and birth, an unborn child undergoes dramatic processes of development. The normal range of gestation is between 37 and 41 weeks. Gestational age is usually dated from the first day of an expectant mother’s last menstrual cycle. 65 66 Both before and after birth, development The cephalocaudal principle, from Latin, meaning “head to tail,” dictates that proceeds according to two fundamental development proceeds from the head to the principles: Growth and motor lower part of the trunk. An embryo’s head, development occur from the top down brain, and eyes develop earliest and are disproportionately large until the other parts and from the center of the body outward. catch up. According to the proximodistal principle, from Latin, meaning “near to far,” development proceeds from parts near the center of the body to outer ones. The embryo’s head and trunk develop before the limbs, and the arms and legs before the fingers and toes 67 68 17  03/10/2024 1. Germinal Stage 2. Embryonic Stage from fertilization to about 2 weeks of from about 2 to 8 weeks gestational age, the zygote divides, the organs and major body systems— becomes more complex, and is implanted respiratory, digestive, and nervous— in the wall of the uterus develop rapidly. This process is known as organogenesis. 69 70 The most severely defective embryos 3. Fetal Stage usually do not survive beyond the first trimester, or 3-month period, of pregnancy. The appearance of the first bone cells at about 8 weeks signals the beginning of the A spontaneous abortion, commonly fetal stage, the final stage of gestation. called a miscarriage, is the expulsion from During this period, the fetus grows rapidly to the uterus of an embryo or fetus that is about 20 times its previous length, and unable to survive outside the womb. organs and body systems become more complex. Right up to birth, finishing touches such as fingernails, toenails, and eyelids continue to develop. 71 72 18  03/10/2024 Fetuses are not passive passengers in their mothers’ wombs. They breathe, kick, turn, flex their bodies, do somersaults, squint, swallow, make fists, hiccup, and suck their thumbs. Scientists can observe fetal movement through ultrasound, the use of high- frequency sound waves to detect the outline of the fetus. Other instruments can monitor heart rate, changes in activity level, states of sleep and wakefulness, and cardiac reactivity. 73 74 A teratogen is an environmental agent, 1. Nutrition and Maternal Weight such as a virus, a drug, or radiation, that can interfere with normal prenatal Pregnant women typically need 300 to 500 development. However, not all additional calories a day, including extra protein. environmental hazards are equally risky Current recommendations are that women who for all fetuses. are underweight should gain 28 to 40 pounds, normal-weight women should gain 25 to 35 pounds, overweight women should gain 15 to 25 pounds, and obese women should gain only 11 to 20 pounds. Women carrying twins or other multiples are advised to gain an additional 14 to 22 pounds, depending on their weight status before becoming pregnant 75 76 19  03/10/2024 2. Malnutrition 3. Physical Activity and Work Malnutrition is a global problem driven by factors Moderate exercise any time during such as poverty, conflict, and climate change, and more recently, by the COVID-19 pandemic. pregnancy does not seem to endanger the Micronutrients are vitamins or minerals that are fetuses of healthy women. needed in small quantities but have a profound Regular exercise reduces constipation and negative effect if absent. Either form of malnutrition during pregnancy is an urgent issue as back pain, and it may lower the risk of it not only can hurt the expectant mother and her complications such as gestational diabetes, child, but also exert effects across generations preeclampsia, or cesarean delivery 77 78 4. Drug Intake Given the issues associated with the use of drugs during pregnancy, why would pregnant women take any medications at all? Medical drugs The use of any drug is a balance of risks and – Among the medical drugs that may be benefits, and at times, the risk of not taking harmful during pregnancy are the antibiotic a drug will outweigh the potential risk to the pregnancy. Recommendations are that no tetracycline; certain barbiturates, opiates, and medication be prescribed for a pregnant or other central nervous system depressants. breast-feeding woman unless it is essential They are linked to birth defects when taken for her health or her child’s. If medication is anytime from the first trimester. necessary, the most effective drug with the fewest side effects should be selected 79 80 20  03/10/2024 4. Drug Intake Fetal alcohol syndrome (FAS) is characterized by a combination of retarded growth, face and body Alcohol malformations, and disorders of the – prenatal alcohol exposure is the most central nervous system. common cause of intellectual disability and the leading preventable cause of birth defects. 81 82 4. Drug Intake 4. Drug Intake Nicotine Caffeine – Women who smoke during pregnancy are – slightly increased risk of miscarriage, stillbirth, more than 1½ times as likely as nonsmokers low birth weight, and other conditions for to bear low-birth-weight babies (weighing less mothers who consume caffeine while than 5½ pounds at birth). pregnant – more like to miscarry or have birth complications, preterm babies, or babies that die from sudden infant death syndrome 83 84 21  03/10/2024 4. Drug Intake 4. Drug Intake Marijuana Cocaine – most commonly used recreational drug during – cocaine use during pregnancy has been pregnancy associated with delayed growth, placental – cite medical concerns, including nausea, displacement, preterm delivery, low birth anxiety, and pain management; subtle weight, small head size, and impaired neurological differences and deficits in neurological development problem-solving skills 85 86 5. Maternal Illnesses Acquired immunodeficiency syndrome (AIDS) is a disease caused by the human immunodeficiency virus (HIV), which prospective parents should try to prevent undermines functioning of the immune all infections—common colds, flu, urinary system. tract and vaginal infections, as well as If an expectant mother has the virus in sexually transmitted diseases. her blood, perinatal transmission may occur: The virus may cross over to the fetus’s bloodstream through the placenta during pregnancy, labor, or delivery or, after birth, through breast milk. 87 88 22  03/10/2024 6. Maternal Emotional State 7. Maternal Age Some tension and worry during pregnancy are The chance of miscarriage or stillbirth rises normal and do not increase risks of birth complications. Moderate maternal anxiety may with maternal age. even spur organization of the developing brain. Women age 30 to 35 are more likely to suffer However, these benefits exert a cost: atypical brain development. A mother’s self-reported stress and complications due to diabetes, high blood anxiety during pregnancy, when chronically high, pressure, or severe bleeding. There is also has been associated with a more active and higher risk of premature delivery, retarded irritable temperament in newborns, negative emotionality and impulsivity, and behavioral fetal growth, birth defects, and chromosomal disorders in early childhood. abnormalities, such as Down syndrome. 89 90 Adolescence, too, carries risk. Adolescent 8. Outside Environmental Hazards mothers tend to have premature or underweight babies—perhaps because a young girl’s still-growing body consumes Pregnant women who regularly breathe air vital nutrients the fetus needs or, more that contains high levels of fine likely, because of inadequate or missing combustion-related particles such as gas prenatal care. fumes and smoke are more likely to bear infants who are premature or undersized, have chromosomal or developmental abnormalities, or are at risk for cognitive and psychomotor delays. 91 92 23  03/10/2024 High stress, a poor diet, or exposure to environmental toxicants such as heavy metals or pesticides can cause epigenetic changes and result in abnormal or poor- quality sperm. Men who smoke have an increased likelihood of transmitting genetic abnormalities and heart defects. Older fathers may be a significant source of birth defects due to damaged or deteriorated sperm. 93 94 95 96 24  03/10/2024 97 25