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Chapter 2 Reading & Study Guide

Chapter 2 Reading & Study Guide - 1 Reading/Study Guide...

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Reading/Study Guide Chapter 2 Genetics, Prenatal Development, and Birth I. Earliest Development and the Foundations of Genetics A. Genes and Chromosomes: The Code of Life 1. Humans begin life as a single cell. a. GENES b. Genes are arranged in specific locations and in a specific order along 46 CHROMOSOMES c. There are tens of trillions of possible genetic combinations. 2. Multiple Births: Two—or More—for the Genetic Price of One a. MONOZYGOTIC TWINS — genetically identical, form when a cluster of cells in the ovum splits off within one week following fertilization ***Identical twins do not run in the family b. DIZYGOTIC TWINS — two separate ova fertilized by 2 separate sperm ***Fraternal twins can run in family but only on mother’s side 1
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(1) Are there any differences in the rate of multiple births? 3. Boy or Girl? Establishing the Sex of the Child a. The 23rd chromosome determines the sex of the child. B. The Basics of Genetics: The Mixing and Matching of Traits a. DOMINANT TRAIT b. RECESSIVE TRAIT 2
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c. GENOTYPE — a person’s genetic heritage; actually genetic material; copied at the time of cell division or reproduction d. PHENOTYPE — the way an individuals genotype is expressed in observed/measured characteristics e. Alleles are genes for traits that may take alternate forms. (1) HOMOZYGOUS — allele contains similar genes from each parent 3
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(2) HETEROZYGOUS — allele contains different forms of genes from parents 2. Most traits are the result of POLYGENIC INHERITANCE — trait influenced by multiple pairs of genes (most human characteristics) Ex. Height, weight, intelligence, skin color a. Some recessive genes are X-LINKED GENES The most recent approach to the study of the effects of heredity on behavior and 4
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development is called BEHAVIORAL GENETICS . C. Inherited and Genetic Disorders: When Development Deviates from the Norm ~Causes: genetics, spontaneous mutation, environmental insult a. Sometimes genes spontaneously change their form, a process called spontaneous mutation . Chromosome Abnoralities - Occurs when chromosomes don’t divide evenly—small pieces of a chromosome(s) may be deleted, duplicated, inverted, misplaced, or exchanged with part of another chromosome Autosomal Abnormalities – mutation in a gene on one of the first 22 nonsex chromosomes Most common: Down Syndrome (Trisomy 21) a. DOWN SYNDROME - single crease across hand, flattened nose, big tongue, almond eyes w/folds - all other genes come from parents - have a combination of features typical of down syndrome and features from parents - intellectual capabilities varies Sex chromosome Abnormalities – occurs when there is a deviation from the typical XX or XY combination of sex chromosomes b. KLINEFELTER’S SYNDROME— (XXY Male) - Males have an extra X chromosome, making them XXY instead of XY (approximately 1 in 1000 live births; the most common sex chromosome disorder) 5
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- characteristics become apparent during puberty (often don't make as much testosterone as other boys) -
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