Chapter 4 Genetic and Congenital Disorders PDF

CHAPTER 4 Genetic and Congenital Disorders Copyright © 2020 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com. Overview  Genetic and congenital disorders affect all ages Copyright © 2020...

CHAPTER 4 Genetic and Congenital Disorders Copyright © 2020 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com. Overview  Genetic and congenital disorders affect all ages Copyright © 2020 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com  Congenital defects – sometimes called birth defects  Genetic disorders may occur from chromosomal, multifactorial, or single-gene disorders  Expression or phenotype (effect) of an altered gene may cause clinical signs  May vary in severity depending on the activity or penetration of the gene Genetic Control  Each human cell contains Copyright © 2020 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com  23 pairs of chromosomes that store its genetic information  22 of these pairs are autosomes  Numbered by size and shape in a karyotype  The final pair consists of the sex chromosomes:  XY for males  XX for females Meiosis  Each sperm and ovum receive only 23 chromosomes during Copyright © 2020 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com meiosis  Once the ovum is fertilized by the sperm:  The zygote that forms has a combined total of 46 chromosomes (23 pairs)  Each individual has a unique identifier:  Their deoxyribonucleic acid (DNA) Genes  Genes matched for a certain function are alleles Copyright © 2020 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com  A genotype describes:  The same chromosomes and genetic content that are contained in each person's body  Not all genes are active in every cell  Gene expression – information encoded – turned into function Gene Processes  A communication link with DNA is known as ribonucleic acid (RNA) Copyright © 2020 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com  When cells are undergoing mitosis in embryonic and fetal development, chromosomes replicate:  Each daughter cell receives identical DNA to the DNA that exists in the parent cell  A mutation (alteration) in genetic material  Can be caused by radiation or harmful drugs  It can also occur spontaneously International Human Genome Project  Gene mapping continues to progress as scientists identify the roles of each human gene Copyright © 2020 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com  The International Human Genome Project goal:  To identify and map every gene on every chromosome  Millions of different pairings have already been listed  There are about 25,000 protein-coding genes The Effects of Genes  Increased knowledge of genetic conditions may lead to improved cures, preventions, and treatment Copyright © 2020 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com  Congenital defects (disorders)  Genetic (inherited) disorders  Developmental disorders  Patterns of inherited genes  Dominant and recessive traits  Predicted using a system known as Punnett squares Single-Gene Disorders  Occur in about 1 out of every 200 live births Copyright © 2020 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com  They are usually classified by their inheritance pattern  Most are dominant, recessive, or X-linked recessive  The risk for these disorders is present with each pregnancy in a family at risk  Not just for one pregnancy Genetic Disorders and Inheritance  Genetic disorders include: Copyright © 2020 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com  Autosomal dominant disorders  Autosomal recessive disorders  X-linked recessive disorders  Multifactorial disorders  Chromosomal disorders Autosomal Dominant Disorders  Some do not become clinically evident until mid-life Copyright © 2020 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com  In these disorders, a defect present in one allele produces clinical expression of the disease  An affected parent has a 50% chance of passing the disorder on to each child  Irrespective of gender Examples of Autosomal Dominant Disorders  Adult polycystic kidney disease Copyright © 2020 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com  Familial hypercholesterolemia  Huntington's disease  Marfan's syndrome Huntington's Disease  An autosomal dominant disorder Copyright © 2020 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com  Causes brain degeneration, developing in mid-life  Characterized by:  Progressive mental deterioration  Abnormal "jerky" movements  Caused by deterioration of neurons in the basal ganglia  Genetic counseling should be given to children of persons with the disease to determine if they carry the abnormal gene  PT – fall prevention, safe ambulation, balance, coordination, wheelchair management, mobility Marfan's Syndrome (1 of 2)  Affects the connective tissue of the body  Usually in the eyes, skeleton, arms, cardiovascular system, Copyright © 2020 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com and joints  Skeletal deformities are most obvious  With the body appearing long and thin  The most dangerous effects include:  Mitral valve prolapse  Aortic valve ring dilation  Weakness of the aorta and other arteries Autosomal Recessive Disorders  Develop when both parents pass on a defective gene Copyright © 2020 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com  This produces an affected (homozygous) child  A child who is heterozygous has received one normal gene and one defective gene  He or she is a carrier  Shows no clinical signs of the disorder Examples of Autosomal Recessive Disorders Copyright © 2020 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com  Albinism  Color blindness  Cystic fibrosis  Phenylketonuria  Sickle cell anemia  Tay-Sachs disease Albinism (1 of 2)  Occurs in 1 of every 38,000 Caucasian births Copyright © 2020 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com  1 in every 22,000 African American births  When two recessive genes are inherited:  Results in a metabolic pathway deficiency related to the production of melanin  An albino's skin appears pale  The hair is white  The irises of their eyes are pink Cystic Fibrosis  An autosomal-recessive disease that often causes death early in life Copyright © 2020 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com  Its most serious symptoms affect:  The lungs (blockage of respiratory passages)  Pancreas (cyst formation that causes degeneration)  CF is very common  1 of every 22 Caucasians carry a gene for the disease Phenylketonuria  PKU is a rare metabolic disorder caused by a liver enzyme deficiency Copyright © 2020 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com  PKU can cause:  Mental retardation  Delayed speech  Microcephaly  Other symptoms of impaired neurologic development  Newborns are routinely screened  For abnormal levels of serum phenylalanine X-linked Disorders  Carried by the female (X) sex chromosome Copyright © 2020 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com  Examples include:  Duchenne muscular dystrophy  Hemophilia A  Female carriers have a 50% chance of  Producing a male child with the disorder  Producing a female child who is a carrier  https://www.cancer.gov/publications/dictionaries/genetics-di ctionary/def/x-linked-recessive-inheritance Hemophilia A  One of the most common inherited bleeding disorders Copyright © 2020 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com  Affecting about 1 out of every 5,000 male live births  It is caused by a deficiency of factor VIII, which is essential for normal blood clotting  When the disease is severe:  Bleeding usually occurs in childhood spontaneously  Have occur several times a month  GI tract, joints – hip, ankle, knee  Can exercise – stretching, resistance training, movement  Avoid contact sports Multifactorial Inheritance Disorders  Examples of multifactorial disorders: Copyright © 2020 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com  Congenital hip dislocation  Cleft lip and palate  Type II Diabetes  Congenital heart disease  Hydrocephalus  Anencephaly Cleft Lip and Cleft Palate  Common birth defects resulting in abnormal facial appearance and speech defects Copyright © 2020 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com  They affect as many as 3.6 babies out of every 1,000 live births in the United States  These defects may present in two ways:  Small notches in the upper lip  Involve complete separation of the palate that extends to the floor of the nose Chromosomal Disorders  Often occur due to an error during meiosis  DNA fragments are displaced or lost Copyright © 2020 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com  More common when the mother is older than age 35  Down syndrome is an example of a trisomy  Meaning that there are three chromosomes instead of two  Occurs at the "21" position (called trisomy 21) Chromosomal Disorders Copyright © 2020 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com  Examples of chromosomal disorders:  Cri du chat syndrome  Down syndrome  Turner's syndrome  Klinefelter's syndrome Down Syndrome (1 of 2)  The most common chromosomal disorder  Occurring in about 1 out of every 800 births Copyright © 2020 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com  The features of this condition include:  Reductions in normal body growth  A head that is smaller and "squared"  A flatter than normal facial profile  A small, depressed nose  Slanted eyes  Malformed ears Down Syndrome (2 of 2)  Patellar dislocation Copyright © 2020 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com  Extreme foot pronation  Scoliosis  In infants & young children  Hypotonia  Joint laxity  Higher risk of developing Alzheimer's  Symptoms by age 40 Turner's Syndrome  Turner's syndrome is caused by an absence of all or part of Copyright © 2020 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com the X chromosome,  It affects about 1 out of every 2,500 live births  It only affects females, causing: Klinefelter's Syndrome (1 of 2)  Klinefelter's syndrome affects males Copyright © 2020 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com  It is described as testicular dysgenesis with presence of one or more extra X chromosomes  It occurs in 1 out of every 500 to 1,000 live births  Symptoms include:  Enlarged breasts,  Less than normal body hair  Small testes  Infertility Developmental Disorders  Developmental disorders may be caused by: Copyright © 2020 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com  Difficult labor or delivery  Premature birth  Exposure to harmful agents  Linked to:  Radiation  Alcohol  Cigarette smoking  Drugs  Maternal infections  T.O.R.C.H.  Routine screening tests for high-risk maternal infections  Toxoplasmosis – infectious disease caused by the protozoan Copyright © 2020 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com Toxoplasma gondii  Other – hepatitis B, mumps, rubeola, gonorrhea, syphilis, varicella  Rubella – nearly eliminated via vaccination  Cytomegalovirus – two-thirds of women of childbearing age have antibodies to this disease  Herpes – acquired as fetus passes through birth canal  If the mother has active genital herpes Musculoskeletal Conditions  Musculoskeletal conditions are some of the more familiar genetic and developmental disorders Copyright © 2020 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com  Diseases range quite widely in severity Congenital Hip Dysplasia  An abnormality of the acetabulum (hip joint) Copyright © 2020 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com  Results in the ball (femoral head) slipping out of the normal position  More common in females  Requires splinting or casting for 2–3 months  It is often due to the baby's position in the womb Teratogenic Agents  There are often no signs that a genetic disorder is present at birth Copyright © 2020 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com  They often occur months or years later  Teratogenic agents, which can cause embryonic or fetal damage, are usually difficult to define  Women are always advised to avoid using drugs or chemicals during childbearing years  In order to avoid teratogenic effects  Ex. Drugs (OTC, prescription, illegal), Infections, environmental chemicals (herbicides), radiation Radiation  Diagnostic levels of radiation do not cause congenital abnormalities Copyright © 2020 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com  Heavy doses of ionizing radiation have been linked to:  Microcephaly  Mental retardation  Skeletal malformations  Radiation can cause inheritable changes in genes and genetic materials  Ex. 13th week gestation – thyroid development in fetus Chemicals and Drugs  Though only rarely linked to developmental defects, environmental chemicals and drugs can cross the placenta to Copyright © 2020 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com damage the embryo or fetus  Documented harm has been caused by:  Substances containing mercury  Lipid-soluble drugs usually cross the placenta more readily, entering the fetal circulation  Drugs such as, cancer treatments, warfarin, certain anticonvulsants, ethyl alcohol & cocaine  Thalidomide – treat nausea & vomiting  Malformation of bones Classes of Teratogenic Drugs  Class A – no risk  Many vitamins, thyroid hormone, pyridoxine, liotrix Copyright © 2020 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com  Class B – slight risk  Acetaminophen, Paracetamol, Amoxicillin, loperamide  Class C – some risk  Rifampicin, theophylline  Class D – significant risk  Phenytoin, tetracycline, paroxetine  Class X – definite risk  Isotretinoin, leflunomide, thalidomide Prenatal Screening and Diagnosis  There are diagnostic tests available to determine certain abnormalities Copyright © 2020 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com  Can be used during various times in life, but particularly in the prenatal period  Examples of commonly screened disorders:  Tay-Sachs disease and sickle cell disease  Diagnostic tools include:  Ultrasonography  Maternal blood tests  Amniocentesis  Chorionic villus sampling Neonatal Testing  Neonates are often tested about 48 hours after birth  Via the pricking of their heels to sample capillary blood Copyright © 2020 by Jones & Bartlett Learning, LLC an Ascend Learning Company. www.jblearning.com  Prompt treatment can prevent mental disability from congenital metabolic disorders  Tested conditions:  Adrenal hyperplasia  Toxoplasmosis  Cystic fibrosis  Hearing function