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Solomon IM Ch 16

Solomon IM Ch 16 - Chapter16: 16 LectureOutline I A ,...

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Chapter 16: The Human Genetics and the Human Genome 165 16 The Human Genetics and the Human Genome Lecture Outline I. The study of human genetics requires alternative methods. A. Chromosomes are identified by karyotyping, analysis of inheritance patterns, pedigree, DNA sequencing, and mapping of genes. B. Studies of pedigrees are problematic because human families are small. C. Karyotyping is the analysis of chromosomes. 1. Cytogenetics is the study of chromosomes and inheritance. a) Cytogenetics is based on studies of humans as well as Drosophila and other organisms. 2. A karyotype shows the composition of the chromosomes of an individual. a) The normal number of chromosomes in humans is 46: 44 autosomes and 2 sex chromosomes. b) In preparing a karyotype, harvested cells are first cultured. c) The cells are then treated with colchicine, which arrests the cells in metaphase, then treated with hypotonic solution and stained to observe the chromosomes. d) Chromosomes can be photographed or visualized using a microscope and a computer, and then are analyzed and identified by size, position of the centromere, banding, and staining regions. e) Chromosomes are also distinguished by FISH (fluorescent in situ hybridization), which can show breakage and fusion of chromosomes that are generally associated with some genetic diseases and cancers. D. Family pedigrees can help identify some inherited conditions. 1. A pedigree is a chart that shows the transmission of genetic traits in a family over several generations. 2. Studying pedigrees enables geneticists to learn more about Mendelian traits. 3. Pedigrees are only useful for studying traits with simple Mendelian inheritance patterns. 4. Characteristics, such as those with genomic imprinting, do not show simple Mendelian patterns of genetics, such as Prader Willi (PWS) and Angelman (AS) syndromes. E. The Human Genome Project is sequencing the DNA on all human chromosomes. 1. In 1999, chromosome 22 (a small chromosome) was the first human chromosome to be completely sequenced. 2. In 2003, the final DNA sequencing of the human genome was completed; the current estimate of the number of genes it contains is less than 30,000. a) What does it all mean?
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Instructor’s Manual for Solomon, Berg, and Martin’s Biology, 9 th Edition 166 3. The problem of sequencing the remaining human chromosomes is complicated by the fact that 95% or more of the genome is noncoding or has unidentified functions to date. a) Many of these sections possibly code for mRNAs that are “potential” genes whose products have never been identified. 4. There are many exciting medical applications utilizing the information obtained from the Human Genome Project. F.
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Solomon IM Ch 16 - Chapter16: 16 LectureOutline I A ,...

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