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Chapter 3

Chapter 3 Summary & Terms

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Psychology 2040A/B
Ian Mac Donald

CHAPTER 3 SUMMARY Principles of Hereditary Transmissiony Development begins at conception when a sperm cell from the father penetrates zygote an ovum from the mother forming a y A normal human zygote contains 46 chromosomes 23 from each parent each of which consists of several thousand strands of deoxyribonucleic acid or DNA genes Genes are the biological basis for the development of the zygote known as into a persony Development of the zygote occurs through mitosisnew body cells are created as the 23 paired chromosomes in each cell duplicate themselves and separate them into two identical new cellsy Specialized germ cells divide by meiosis to produce gametes sperm or ova that each contains 23 unpaired chromosomes Crossingover and the independentof chromosomes ensure that each gamete receives a unique set of assortmentgenes from each parenty Monozygotic or identical twins result when a single zygote divides to create two cells that develop independently into two individualsy Dizygotic or fraternal twins result when two different ova are each fertilized by a different sperm cell then develop independently into two individuals y Gametes contain 22 autosomes and 1 sex chromosome Females sex chromosomes are both X chromosomes males sex chromosomes are an X and a Y chromosomeX chromosome Sperm contain either an X or Y chromosome y Ova contain an Therefore fathers determine the sex of their children depending on whether the sperm that fertilizes the ova contains an X or a Y chromosome y Genes produce enzymes and other proteins that are necessary for the creation and functioning of new cells and regulate the timing of development Internal and external environments influence how genes functiony There are many ways in which ones genotype may affect phenotypethe way one looks feels thinks or behaves alleles one of which is y Some characteristics are determined by a single pair of inherited from each parento In simple dominantrecessive traits the individual displays the phenotype of dominant allelethe o If a gene pair is codominant the individual displays a phenotype in between recessive allelesthose produced by the dominant and the o Sexlinked characteristics are those caused by recessive genes on the X chromosome when there is no corresponding gene on the Y chromosome to mask its effects they are more common in malesy Most complex human attributes such as intelligence and personality traits are polygenic or influenced by many genes rather than a single pair Hereditary Disorders
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