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Social Sci LibreTexts

2: Theories, Genetics, and Prenatal Development

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    • 2.1: Historical Theories on Development
    • 2.2: Contemporary Theories on Development
    • 2.3: Heredity
      As your recall from chapter one, nature refers to the contribution of genetics to one’s development. The basic building block of the nature perspective is the gene. Genes are recipes for making proteins, while proteins influence the structure and functions of cells. Genes are located on the chromosomes and there are an estimated 20,500 genes for humans, according to the Human Genome Project.
    • 2.4: Genotypes and Phenotypes
      The word genotype refers to the sum total of all the genes a person inherits. The word phenotype refers to the features that are actually expressed. Because genes are inherited in pairs on the chromosomes, we may receive either the same version of a gene from our mother and father, that is, be homozygous for that characteristic the gene influences. If we receive a different version of the gene from each parent, that is referred to as heterozygous.
    • 2.5: Genetic Disorders
      Most of the known genetic disorders are dominant gene-linked; however, the vast majority of dominant gene linked disorders are not serious or debilitating. For example, Huntington's Disease is a dominant gene linked disorder that affects the nervous system and is fatal, but does not appear until midlife. Recessive gene disorders, such as cystic fibrosis and sickle-cell anemia, are less common but may actually claim more lives.
    • 2.6: Chromosomal Abnormalities
      A chromosomal abnormality occurs when a child inherits too many or two few chromosomes. The most common cause of chromosomal abnormalities is the age of the mother. As the mother ages, the ovum is more likely to suffer abnormalities due to longer term exposure to environmental factors. Consequently, some gametes do not divide evenly when they are forming. Therefore, some cells have more than 46 chromosomes.
    • 2.7: Prenatal Development
      Now we turn our attention to prenatal development which is divided into three periods: The germinal period, the embryonic period, and the fetal period. The following is an overview of some of the changes that take place during each period.
    • 2.8: Tetratogens
      The developing child is most at risk for some of the most severe problems during the first three months of development. Unfortunately, this is a time at which many mothers are unaware that they are pregnant. Today, we know many of the factors that can jeopardize the health of the developing child. The study of factors that contribute to birth defects is called teratology. Teratogens are environmental factors that can contribute to birth defects.
    • 2.9: Maternal Factors
      Most women over 35 who become pregnant are in good health and have healthy pregnancies. However, according to the March of Dimes (2016d), women over age 35 are more likely to have an increased risk of: Fertility problems High blood pressure Diabetes Miscarriages Placenta Previa Cesarean section Premature birth Stillbirth A baby with a genetic disorder or other birth defects.
    • 2.10: 2.9 Prenatal Assessment
      A number of assessments are suggested to women as part of their routine prenatal care to find conditions that may increase the risk of complications for the mother and fetus (Eisenberg, Murkoff, & Hathaway, 1996). These can include blood and urine analyses and screening and diagnostic tests for birth defects.
    • 2.11: Complications of Pregnancy