chapter 2 - PSY 231 Developmental Psychology Chapter 2...

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PSY 231 Developmental Psychology: Chapter 2 Biological and Environmental Foundations A. Phenotypes- observable characteristics that depend on an individual’s genotype a. Also affected by each person’s lifelong history of experiences B. Genotype –the complex blend of genetic information that determines our species and influences all our species and influences all our unique characteristics Genetic Foundations A. Chromosomes –rod like structures that store and transmit genetic information a. Humans have 23 matching pairs One inherited from the mother and one from the father 1. Genetic Code A. Chromosomes are made up of deoxyribonucleic acid or DNA a. a long, double-stranded, chemical molecule that looks like a twisted ladder b. consisting of a specific pair of chemical bases joined together between the two sides c. provides genetic instruction d. can duplicate itself in the form of mitosis which permits the one-celled fertilized ovum to develop into a complex human composed of billions of cells B. Gene –segment of DNA along the length of the chromosome a. Genes accomplish their task by sending instructions for making a rich assortment of proteins to the cytoplasm or the area surrounding the cell nucleus -Proteins trigger chemical reactions throughout the body and are the biological foundation on which out characteristics are built C. We share our DNA with many other animals (98% of chimp and human DNA is identical) 2. Sex Cells A. Gametes- sex cells or the sperm and ovum a. Formed through meiosis which is a process of cell division when half of the number of chromosomes normally present in body cells -Ensures that the constant quantity of genetic material is transmitted from one generation to the next -A healthy man can father a child at any age after sexual maturity Four sperm are produced when meiosis is complete The cells from which sperm arise are produced continuously throughout life - healthy man can father a child at any age after sexual maturity -The female is born with the ova already present in her ovaries but she can bear children for only three to four decades but there are still plenty of female cells 1 to 2 million is present at birth 40,000 remain at adolescence 350 to 450 will mature during childbearing years 1
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PSY 231 b. Sperm and ovum unit at conception and the cell that results is called the zygote -Zygotes have 46 chromosomes 3. Boy or Girl? A. 22 of the 23 pairs of chromosomes are matching pairs called autosomes B. The 23 rd pair consists of sex chromosomes a. Females have XX and males have XY b. X genes is a relatively large chromosome whereas the Y is short and carries little genetic material 4. Multiple Births A. Fraternal twins –dizygotic are the most common type of multiple birth resulting from the release and fertilization of two ova a. No more similar than two siblings b. Maternal factors linked to fraternal twinning – ethnicity (most common in the African American race with 12 to 16 per 1000 births), family history
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