Lab 28 Lab Instructions Scientists, enabled by the Human Genome Project, are churning out an unprecedented volume of data on human chromosomes and the tens of thousands of genes residing on them, many associated with genetic disorders. These data, and many Web sites on human genetic disorders, are freely accessible on the Internet. Gene Gateway, originally designed as a Web companion to the popular Human Genome Landmarks poster, is a collection of guides and tutorials designed to help students and other novice users get started with some of the resources that make these data available to the public. You will be using one of these resources to complete your lab. 1. Go to the following Website. When ‘online’ you can click the address below. If that does not work, copy/paste the address into your ‘Browser’. 2. The ‘Legend’ is below. You will need it to answer the first question on the lab report. Legend: Magenta and green. These regions reflect the unique patterns of light and dark bands seen on human chromosomes that have been stained to allow viewing through a light microscope. Red. The centromere, or constricted portion, of each chromosome. Yellow. Chromosomal regions that vary in staining intensity and are sometimes called heterochromatin (meaning “different color”). Yellow with thin magenta horizontal lines. (e.g., on chromosome 21) denote variable regions, called stalks, that connect a very small chromosome arm (a “satellite”) to the chromosome. 3. Use the “Chromosome Viewer” at the bottom of the Web page (use the link in #1 of this lab) and the “List of Chromosomes” to complete the remainder of the lab report. (Examples of what you are looking for are shown below.) THIS IS NOT AN ACTIVE LINK. IT IS HERE TO HELP YOU FIND THE VIEWER WHEN YOU CLICK ON THE LINK LISTED IN ABOVE IN #1 OF THIS LAB! Click on any chromosome below to see a list of selected traits and disorders associated with that chromosome. Chromosome 1 Chromosome 2 Chromosome 3 Chromosome 4 Chromosome 5 Chromosome 6 Chromosome 7 Chromosome 8 Chromosome 9 Chromosome 10 Chromosome 11 Chromosome 12 Chromosome 13 Chromosome 14 Chromosome 15 Chromosome 16 Chromosome 17 Chromosome 18 Chromosome 19 Chromosome 20 Chromosome 21 Chromosome 22 Chromosome X Chromosome Y What are genetic disorders? Both environmental and genetic factors have roles in the development of any disease. A genetic disorder is a disease caused by abnormalities in an individual’s genetic material (genome). There are four different types of genetic disorders: (1) single-gene, (2) multifactorial, (3) chromosomal, and (4) mitochondrial. (1) Single-gene (also called Mendelian or monogenic) – This type is caused by changes or mutations that occur in the DNA sequence of one gene. Genes code for proteins, the molecules that carry out most of the work, perform most life functions, and even make up the majority of cellular structures. When a gene is mutated so that its protein product can no longer carry out its normal function, a disorder can result. There are more than 6,000 known single-gene disorders, which occur in about 1 out of every 200 births. Some examples are cystic fibrosis, sickle cell anemia, Marfan syndrome, Huntington’s disease, and hereditary hemochromatosis. Single-gene disorders are inherited in recognizable patterns: autosomal dominant, autosomal recessive, and X-linked. More information on the different modes of inheritance is available from the following Web sites: Inheritance of Single Gene Defects – From the The Merck Manual of Diagnosis and Therapy. Genetic Disorders: Types of Inheritance – From Gene Stories provided by BBC. Inheritance Patterns of Monogenic Disorders – From the Genetic Interest Group in the U.K. Genetics – From the Medical Encyclopedia at MEDLINEplus. (2) Multifactorial (also called complex or polygenic) – This type is caused by a combination of environmental factors and mutations in multiple genes. For example, different genes that influence breast cancer susceptibility have been found on chromosomes 6, 11, 13, 14, 15, 17, and 22. Its more complicated nature makes it much more difficult to analyze than single-gene or chromosomal disorders. Some of the most common chronic disorders are multifactorial disorders. Examples include heart disease, high blood pressure, Alzheimer’s disease, arthritis, diabetes, cancer, and obesity. Multifactorial inheritance also is associated with heritable traits such as fingerprint patterns, height, eye color, and skin color. (3) Chromosomal – Chromosomes, distinct structures made up of DNA and protein, are located in the nucleus of each cell. Because chromosomes are carriers of genetic material, such abnormalities in chromosome structure as missing or extra copies or gross breaks and rejoinings (translocations), can result in disease. Some types of major chromosomal abnormalities can be detected by microscopic examination. Down syndrome or trisomy 21 is a common disorder that occurs when a person has three copies of chromosome 21. (4) Mitochondrial – This relatively rare type of genetic disorder is caused by mutations in the nonchromosomal DNA of mitochondria. Mitochondria are small round or rod-like organelles that are involved in cellular respiration and found in the cytoplasm of plant and animal cells. Each mitochondrion may contain 5 to 10 circular pieces of DNA. Lab Report 28 Complete this lab using the computer link in the lab instructions for lab 28. 1. What do the following regions on the legend represent? magneta and green red yellow yellow with thin magenta horizontal lines 2. Click on chromosome 1. How many bases does it contain? 3. Click on each of the other chromosomes. Which chromosome has the fewest number of bases? 4. Click on chromosome 1. Right click and ‘mouse over’ the image to “zoom in”. List two diseases that are associated with markers on this chromosome. 1. 2. 5. Continue using this process on each of the other listed chromosomes. chromosome 3 1. 2. chromosome 6 1. 2. chromosome 12 1. 2. chromosome 18 1. 2. chromosome 21 1. 2. chromosome X 1. 2. chromosome Y 1. 2.

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