UNIT 13 (OPTION) Genetic Abnormalities

Transcription

1 Unit 13 Genetic Abnormailities 1 UNIT 13 (OPTION) Genetic Abnormalities Originally developed by: Hildur Helgedottir RN, MN Revised (2000) by: Marlene Reimer RN, PhD, CCN (C) Associate Professor Faculty of Nursing University of Calgary & Associate in Nursing Calgary Regional Health Authority

2 Unit 13 Table of Contents Overview...4 Aim...4 Objectives...4 Resources...4 Web Links...5 Section 1: Genetic Abnormalities...6 Learning Activity #1: Self-Assessment Questions...6 Learning Activity #2: Case Study Genetics...8 Genetic Counselling...9 Learning Activity #3: Post Test...10 Final Thoughts...11 References...12 Checklist of Requirements...13 Answers to Learning Activities...14 Learning Activity #1: Self Assessment...14 Learning Activity #3: Post Test...15

3 Unit 13 Genetic Abnormailities 3 UNIT 13 Genetic Abnormalities Genetic and chromosomal disorders affect all age groups and can involve any body organ or tissue in the human body. Gaining a comprehensive understanding of the nature and consequences of these disorders therefore has direct implications for nurses working in any setting. In addition to working with clients suffering from diseases secondary to genetic abnormalities, nurses also have an increasing role to play in the rapidly advancing field of genetic counselling and prenatal diagnosis. Sound knowledge of the pathophysiology of genetic disorders is therefore an important aspect of nursing in today s health care system. Genetics has become one of the hottest areas for basic medical research in the nineties. Evidence is rapidly accumulating that genetic patterns are among the multiple factors which affect susceptiblity to certain diseases.

4 4 Unit 13 Genetic Abnormalities Overview Aim The aim of this unit is to facilitate your understanding of how genetic and chromosomal abnormalities may develop and how these disorders can be expressed as disease. While completing this unit you are expected to become familiar with the terminology specific to this field of study and be able to use this terminology to describe the development and implications of specific disorders. Objectives Upon completing this unit you will be able to: 1. Define common genetic terms 2. Describe mechanisms by which genetic abnormalities may develop 3. Explain ways in which genetic abnormalities may be manifested 4. Briefly describe genetic counselling, including methods for genetic screening and prenatal diagnosis Resources Requirements Review: Mitosis and meiosis as basics for genetics. McCance and Huether (2001), p. 123, Figure 4-7 provide a detailed diagram of meiosis. If you wish to review cell structure and division more thoroughly, refer to Chapter 1 in the course text. Read: McCance and Huether (1998), pp. 115, , , , (skim with attention to the definition of terms.) Print Companion: Genetic Abnormalities Learning Activities Learning Activity #1: Self-assessment Learning Activity #2: Case Study Learning Activity #3: Post Test Rankin, Reimer & Then revised edition. NURS 461 Pathophysiology, University of Calgary

5 Unit 13 Genetic Abnormailities 5 Supplemental Materials Raff, B. (1994). Nursing and genetics for the 21st century. JOGNN, 23(6), This article provides an excellent review of basic knowledge, explains new information about genetics and heredity. Bulletin of the Hereditary Diseases Program of Alberta. Available in LRC or by writing to: Editorial Office Bulletin of Hereditary Diseases Program Alberta Children s Hospital 1820 Richmond Rd. SW Calgary, Alberta, T2T 5C7 Note: There is no glossary or acronym list for this unit because we suggest that you make your own as you work through the required readings and learning activities. Web Links All web links in this unit can be accessed through the Web CT system.

6 6 Unit 13 Genetic Abnormalities Section 1: Genetic Abnormalities Learning Activity #1: Self-Assessment Questions Complete the following questions, based on the required readings. Answers are provided at the end of this unit. 1. What are the roles of genes in the human body? 2. Define the following: a. chromatin b. gene expression c. genotype d. phenotype e. karyotype Rankin, Reimer & Then revised edition. NURS 461 Pathophysiology, University of Calgary

7 Unit 13 Genetic Abnormailities 7 3. Differentiate between the following disorders and give an example of each: a. autosomal dominant b. autosomal recessive c. X-linked recessive 4. Answer the following questions: a. What are chromosome disorders and why do they occur? b. Name three syndromes resulting from chromosomal disorders. Explain the cause of each abnormality.

8 8 Unit 13 Genetic Abnormalities Learning Activity #2: Case Study Genetics Mr. and Mrs. Tandy are 42 years old and have been married for 19 years. They have two daughters (15 and 17 years of age), both are healthy high school students. Mr. Tandy is an only child. Mrs. Tandy had a younger brother who had Hemophilia A and required frequent blood transfusions until he died of AIDS in One week ago, Mrs. Tandy found out that she is pregnant. According to ultrasound she is seven weeks into this unplanned, unexpected pregnancy. Although the couple is delighted at the prospect of having a new baby, they nevertheless have some serious concerns regarding the health of their unborn baby. 1. What are the two primary concerns regarding the Tandy s unborn baby? Why? 2. What is the likelihood of the Tandy s daughters being carriers of Hemophilia A? Draw a genogram if helpful. Rankin, Reimer & Then revised edition. NURS 461 Pathophysiology, University of Calgary

9 Unit 13 Genetic Abnormailities 9 Genetic Counselling Genetic counselling is the process by which patients relatives at risk of a disorder that may be hereditary are advised of the consequences of the disorder, the probability of developing and transmitting it, and the ways in which it may be prevented or ameliorated. The Alberta Hereditary Diseases Program Genetic Counselling Program at Alberta Children's Hospital is an excellent resource. Stages in Genetic Counselling 1. Precounselling Assessment Diagnosis, Family History, Special Tests (chromosomes, etc,) 2. Recurrence Risk Estimation Based on pedigree analysis, medical literature, test results 3. Communication Nature and consequences of disorder recurrence risk, treatment (if available) preventive measures (prenatal diagnosis, artificial insemination by donor, etc.) 4. Follow-up Written reports to referring physician and consultant. Referral to appropriate health care agencies, self help organizations, etc. as require Who should consider genetic counselling? 1. Individuals who have a birth defect or genetic disorder. 2. Couples with a child or close relative who has a birth defect, mental retardation or a genetic disorder. 3. Couples in which the woman is over 34 years and who are planning a pregnancy. 4. Couples who have had three or more miscarriages or stillbirths. 5. Individuals at risk for late onset genetic disorders, (e.g., familial hypercholesterolemia) 6. Individuals who could be carriers for such disorders as sickle cell disease or Tay-Sachs disease, because of their ethnic background.

10 10 Unit 13 Genetic Abnormalities Prenatal Diagnosis: Amniocentesis Chorionic Villi Sampling Learning Activity #3: Post Test Match the type of genetic problem in the first column with the correct disease example(s) in the second. Answers can be found at the end of this unit. Genetic Problem A. Chromosome error B. Single gene inheritance autosomnal dominant C. Single gene inheritance autosomnal recessive D. X-linked inheritance Disease Tay-Sachs disease Neurofibromatosis Huntington disease Hemophilia Prader-Willi syndrome E. Multifactorial inheritance Rankin, Reimer & Then revised edition. NURS 461 Pathophysiology, University of Calgary

11 Unit 13 Genetic Abnormailities 11 Final Thoughts The principles of genetic and chromosomal abnormalities have been reviewed. An understanding of these principles provides the basis for applying this knowledge to specific disorders expressed as a result of genetic and chromosomal defects. The rapid advances in the field of genetics and prenatal diagnosis makes it imperative for nurses to remain current.

12 12 Unit 13 Genetic Abnormalities References Conover, E. (1994). Hazardous exposures during pregnancy. JOGNN, 23(6), Forsman, I. (1994). Evolution of the nursing role in genetics. JOGNN, 23(6), Gore Olsen, D. (1994). Parental adjustment to a child with genetic disease: One parent s reflections. JOGNN, 23(6), Jones, S. L. (1994). Assisted reproductive technologies: Genetic and nursing implications. JOGNN, 23(6), Mackta, J., & Weiss, J. O. (1994). The role of genetic support groups. JOGNN, 23(6), McCance, K., & Huether, S. (2001). Pathophysiology: The biologic basis for disease in adults and children (4 th ed.). St. Louis: Mosby. Penticuff, J. (1994). Ethical issues in genetic therapy. JOGNN, 23(6), Raff, B. S. (1994). The Genome Project. JOGNN, 23(6), Raff, B. S. (1994). Nursing and genetics for the 21st century. JOGNN, 23(6), Ross, L. J. (1994). Developmental disabilities: Genetic implications. JOGNN, 23(6), Wright, L. (1994). Prenatal diagnosis in the 1990s. JOGNN, 23(6) Rankin, Reimer & Then revised edition. NURS 461 Pathophysiology, University of Calgary

13 Unit 13 Genetic Abnormailities 13 Checklist of Requirements Read Print Companion: Genetic Abnormalities Read McCance & Huether, pp. 115, , , , Learning Activity #1: Self-Assessment Question Learning Activity #2: Case Study Learning Activity #3: Post Test

14 14 Unit 13 Genetic Abnormalities Answers to Learning Activities Learning Activity #1: Self Assessment 1. Genes determine the types of proteins and enzymes that are made by the cells, and they control inheritance and the day to day function of all the cells in the body. 2. a. Chromatin is the DNA molecule combined with several types of protein and small amounts of RNA. During cell division the chromatin coils and folds over to form chromosomes. (see McCance & Huether, p. 114). b. Gene expression is a term used to refer to the degree to which a gene or particular group of genes is active. Gene expression is controlled by induced and repressor substances. c. The genotype of an individual is a term for the genetic information stored in the base sequence triplet code (see McCance & Huether, 2001, p. 132). d. The phenotype refers to the recognizable traits, physical or biochemical, that are associated with a specific genotype. 3. These are all so called single gene disorders. In autosomal dominant disorders, an affected parent has a single mutant gene that is transmitted to the child regardless of sex. In autosomal recessive disorders, both parents are usually unaffected, but are carriers for the defective gene. The disorder affects children of both sexes. The most common pattern of inheritance in X-linked recessive disorders is seen in an unaffected mother who carries one normal and one mutant allele on the X-chromosome (see pp. 133, 139). 4. Chromosome disorders involve a change in chromosome number or structure that results in damage to sensitive genetic mechanisms or in reproductive disorders. Examples include Turner s syndrome (monosomy of the X chromosome), Trisomy 21 (Down s syndrome) which refers to polysomy of autosomes 21, and Polysomy X (Klinefelter s syndrome) characterized by an extra X chromosome in a male (X/X/Y). Rankin, Reimer & Then revised edition. NURS 461 Pathophysiology, University of Calgary

15 Unit 13 Genetic Abnormailities 15 Learning Activity #3: Post Test C Tays-Sachs disease. An autosomnal recessive disease which is very common among people of Jewish ancestry (see McCance & Huether, 2001 p. 578). B Neurofibromatosis. An autosomal dominant disorder noted for variable expressivity (see McCance & Huether, 2001 pp ). B Huntington disease. An autosomal dominant disorder noted for delayed age of onset (see McCance & Huether, 2001 p. 144). D Hemophilia. A type of recessive single gene inheritance which is X-linked (see McCance & Huether, 2001 pp ). A Prader-Willi syndrome. Deletion of part of chromosome 15 from the father (see McCance & Huether, 2001 p. 136). E Cleft lip and palate. Usually caused by multiple factors, genetic and non-genetic (see McCance & Huether, 2001 pp ). A Down s syndrome. Three copies of chromosome 21 (see McCance & Huether, 2001 pp ). D Duchenne muscular dystrophy. A type of single gene inheritance which is x-linked (see McCance & Huether, (2001 pp ; ; ). E Menigiocele. A type of neural tube defect which results when the threshold of lability is crossed through a combination of genetic and environmental influences e.g. folic acid deficiency (see McCance & Huether, 2001 pp ).