Genetic Counseling PDF

Maternal AND CHILD HEALTH NURSING LECTURE GENETIC ASSESSMENT AND COUNSELING GENOME 1 in 20 newborn inherit genetic disorders is the complete set of genes present in a cell. 23 70% of pediatric admission have some form of pairs of...

Maternal AND CHILD HEALTH NURSING LECTURE GENETIC ASSESSMENT AND COUNSELING GENOME 1 in 20 newborn inherit genetic disorders is the complete set of genes present in a cell. 23 70% of pediatric admission have some form of pairs of chromosomes ( 3.1 billion DNA sequences genetic disorder each) Genetics Is the study of the way such disorders occur INHERITANCE OF DISEASE Study of genes, genetics variation and heredity. A. Autosomal Dominant Disorders Genetics disorder With an autosomal dominant condition, either a Disorders that can be passed from one generation to person has two unhealthy genes ( is homozygous the next because they result from some disorders in dominant ) or is heterozygous, with the gene causing the gene or chromosome structure. the disease stronger or more dominant than the Occur in some ethnic groups corresponding healthy recessive gene for the same Occur the moment an ovum and sperm fuse or even trait. earlier 50% of spontaneous miscarriage are result of Mendelian Inheritance: Dominant & Recessive chromosomal disorder Patterns Cytogenetics Discovered & described by Gregor Mendel in the Is the study of chromosomes by light microscopy and 1800 the method by which chromosomal aberrations are When dominant genes are paired with a non identified dominant( recessive) ones, the dominant genes are Karotype always expressed in preference to the recessive A graphic representation of the chromosome genes two like genes in the chromosomes are called NATURE OF INHERITANCE ALLELES Genes For each of character, an organism inherits two basic unit of heredity that determine both the alleles, one from each parent physical and cognitive characteristics of people An organism is HOMOZYGOUS for that gene if both Composed of segment of DNA, which are interwoven alleles are identical( Both dominant or recessive) into strands in the nucleus of the body cells to form a An organism is HETEROZYGOUS for that gene if the CHROMOSOMES alleles are different. (one dominant or one recessive) CHROMOSOMES INHERITANCE OF DISEASE Threadlike structure of nucleic acid and protein found in the nucleus of living cells that carries the genetic information called genes each cell contains 46 chromosomes ( 23 pairs)  22 autosomes  1 sex chromosome ( XX Female /XY male) PHENOTYPE refers to a person’s appearance or the expression of genes. observable characteristic of an individual GENOTYPE refers to a person’s actual gene composition 1 genetic counseling  Maternal AND CHILD HEALTH NURSING LECTURE TYPES OF GENETIC DISEASES c. Huntington Disease 1. Disorders with multifactorial inheritance (polygenic) rare, inherited disease that causes the progressive 2. Monogenic/ medelian disorder breakdown (degeneration) of nerve cells in the brain. 3. Chromosomal aberration has a broad impact on a person's functional abilities and usually results in movement, thinking (cognitive) 1. DISORDERS WITH MULTIFACTORIAL and psychiatric disorders. INHERITANCE (POLYGENIC) 3. CHROMOSOMAL ABERRATION A genetic disorder that is caused by the combined CHROMOSOMES are big DNA molecules action of more than one gene. composed of genes. These chromosomes are Environmental conditions combine with these located in the cell nucleus. mutations can form a certain disease problem. Abnormalities in their structure or number can cause Example: Alzheimer’s, diabetes, hypertension, some of the most dangerous genetic disorders Arthritis, obesity. Examples: Down Syndrome 2. MONOGENIC/ MEDELIAN DISORDER COMMON GENETIC DISORDERS Inheritance pattern which determines a particular Turner’s syndrome trait by one set of alleles or specific genes. Genetic condition that only affects females Single gene genetic disorder. This condition is caused by an abnormal Almost 6000 known single-gene disorders. 1 in every chromosome and affects about one in every 2500 200 newborn have single gene disorder baby girls, but is much more common among Sickle cell anemia, cystic fibrosis, Huntington pregnancies that do not survive to term Disease (miscarriage and stillbirths) Named after Dr. Henry Turner, the endocrinologist a. Sickle cell disease in year 1938 Recessive genetic blood disorder with over Causes: dominance, characterized by RBC that assume and  Nondisjunction abnormal, rigid, sickle shape. Sickling decreases the  A pair of sex chromosome fails to separate during cell’s flexibility and results in a risk of various the formation of egg or sperm so when an abnormal complications. The sickling occurs because of a egg unites with a normal sperm to form an embryo mutation in the hemoglobin gene. ends up missing one of the sex chromosome (X SCD may lead to various acute and chronic rather than XX) complications, several of which have a high mortality  “45X” meaning that an individual has 44 autosomes rate. Sickle cell disease is prevalent in many parts of and a single X chromosome India, where the prevalence has ranged from 9.4 to How common? 22.2% in endemic areas.  Affects 71000 females in US Blood transfusions are often used in the  Most pregnancies that are affected by TS results in management of sickle cell disease in acute cases miscarriages 10% of miscarriages are caused by TS and to prevent complications by decreasing the  1/2500 female births are related to turner syndrome number of RBC that can be sickle by adding normal Dx of TS RBC TS may be suspected in pregnancy during an UTZ Normal life span of RBC: 120 days test. This can be confirmed by prenatal testing b. Cystic fibrosis amniocentesis- to obtain cells from the unborn baby Excessive mucus secretion for chromosomal analysis. If a diagnosis is confirmed Decrease in production of sweat because of the prenatally, the baby may be under the care of sweat glands and digestive juices are affected specialist pediatrician immediately after birth 2 genetic counseling  Maternal AND CHILD HEALTH NURSING LECTURE Diagnosis is confirmed by a blood test called attaches to another chromosome (usually karyotype. This is used to analyse the units that chromosome 14) make up the child’s chromosomes How common? For a child with TS, the earlier the diagnosis, the There are three types of a DS: Trisomy 21 better the prospects for treatment. Children who are (nondisjunction) accounts for 95% of cases, shorter than normal are often seen by a pediatric translocation accounts for about 4% and mosaicism endocrinologist, who is a doctor specializing in accounts for about 1% treating children with growth problems One in every 691 babies in the US is born with DS There are more than 400000 people living with DS in Down syndrome (trisomy 21) the US. DS occurs in people of all races and Dr. John Langdon Down described the syndrome in economic levels. The incidence of births of children 1866 with DS increases with the age of the mother. But One of the first symptom complexes associated with due to higher fertility rates in younger women, 80% of mental retardation to be identified as a syndrome children with DS are born to women under 35 years A congenital condition caused by an extra of age chromosome. The presence of an extra number 21 Dx for DS chromosomes causes the distinctive facial features, Diagnosed one of two ways, either during pregnancy physical characteristics and the cognitive or shortly after birth. The dx is always based on the impairments seen in people with DS presence of an extra number 21 chromosome on a May have variety of birth defects. About half of all karyotype affected children are born with a heart defect. The dx of DS is usually made soon after birth Digestive abnormalities, such as a blockage of the because of some subtle differences in the baby’s intestine appearance Individuals with DS have an increased risk of If the doctor suspects that the baby has DS, a developing several medical conditions. These chromosome test called a karyotype, will be ordered. include gastroesphageal reflux, which is a backflow It usually takes a few days to get the results of this of acidic stomach contents into the esophagus blood test. It is almost always a shock when a baby is Delayed development and behavioral problems are diagnosed with DS. often reported in a children with DS Treatment for DS Causes: Providing support and treatment for a patient with DS The most common form of DS is known as Trisomy is meant to improve their quality of life 21,a condition where individuals have 47 Medical conditions associated with DS, including chromosomes in each cell instead of 46. those affecting the heart or the gastrointestinal This is caused by an error in cell division called system, may require evaluation and care, sometimes nondisjunction, which leaves a sperm or egg cell with requiring surgery an extra copy of chromosome 21 before or at As the patient ages, the care and support needed will conception. Trisomy 21 accounts for 95% of DS depend upon the intellectual ability and physical cases, with 88% originating from nondisjunction of function achievable by the individual the mother’s egg cell. 5% of DS cases are due to conditions called Klinefelter’s syndrome mosaicism and translocation. Mosaic DS results Also known as XXY syndrome, is a fairly common when some cells in the body are normal while others genetic condition found in males only.Many boys have trisomy 21. with KS have no sign or symptoms, and some don’t Robertsonian translocation occurs when part of even know they have it until later in life chromosome 21 breaks off during cell division and Typically causes a boy’s testicles to grow at a slower rate than those of the other boys. It prevents testicles 3 genetic counseling  Maternal AND CHILD HEALTH NURSING LECTURE from producing normal amounts of sperm and the b) A couple whose close relatives have a child with hormone testosterone genetic disorders such as translocation disorder or Named after Dr. Henry Klinefelter, who is described an inborn error of metabolism as a group of symptoms found in some men with the c) Any individual who is a known balance translocation extra X chromosome. Even though all men with carrier Klinefelter syndrome have the extra X chromosome, d) Any individual who has an inborn error of metabolism not ever XXY male has all of those symptoms or chromosomal disorder Causes: e) A consanguineous couple Men with KS have an extra X chromosome f) Any woman older than 35 years and any man older Of the 23 pairs of chromosomes, one pair is called than 55 years the sex chromosomes because they determine a g) Couples of ethnic backgrounds in which specific person’s sex. One sex chromosome is inherited from illnesses are known to occur. the mother and the other from the father. Mother always pass on an X or a Y chromosome NURSING RESPONSIBILITIES The normal male chromosome arrangement is 46XY, 1. Explain to a couple what procedures they can expect but men with KS have 47XXY. The extra X to undergo chromosome can come from wither parent 2. Explain how different genetic screening tests are How common? done and when they are usually offered Between 1 in 500 and 1 in 1000 boys are born with 3. Support couples while waiting for the test results KS 4. Assist couples in values clarification, planning, and decision making based on test results FINAL CONCLUSION 5. Explain chances like 25% a child can have the a. Turner’s syndrome: is genetic abnormality in which disease. out of 46 chromosomes there are 44 autosomes and a single X chromosome (X rather than XX) ASSESSMENT OF GENETIC DISORDERS b. Down’s syndrome: is also known as trisomy 21 in I. HISTORY which individual has 47 chromosomes instead of 46  Family history including half brothers and sisters c. Klinefelter’s syndrome: is also known as XXY  Mother’s age syndrome normal male chromosome arrangement is  Relationship of parents 46XY, but men with Klinefelter’s syndrome have  Ethnic background 47XXY  Previous history of pregnancy (abortion or miscarriages without reason) GENETIC COUNSELING PURPOSES:  Prenatal history 1. Provide a concrete, accurate information about the II. PHYSICAL ASSESSMENT process of inherited disorders Inspection 2. Reassure people who are concerned that their child Characteristic Probable syndrome may inherit a particular disorder and that the disorder Slant of eye Down syndrome will not occur Overriding of finger Trisomy 18 3. Allow people who are affected by inherited disorders Webbed neck Turner syndrome to make informed choices about future reproduction Absence of secondary sex Klinefelter’s syndrome 4. Offer support to people who are affected by genetic characteristic disorders Large tongue Down syndrome Who are subjected to Genetic counseling? Late clossure of the Down syndrome a) A couple who has a child with congenital disorder or fontanels an inborn error of metabolism 4 genetic counseling  Maternal AND CHILD HEALTH NURSING LECTURE Trisomy 13 CHORIONIC VILLI SAMPLING (Procedure) The chorion is located by ultrasound Intravaginally ↓ A thin catheter is inserted intravaginally or abdominally The cells removed in CVS are karyotyped for DNA analysis to reveal whether the fetus has a genetic disorder Results are available immediately NURSING CARE: III. DIAGNOSTIC TESTING 1. Explain the procedure and risk A. KARYOTYPING 2. After CVS, instruct the woman to report chills, fever, A laboratory test used to study an individual's uterine contraction or bleeding chromosome make-up. Chromosomes are separated 3. Inform parents about disorders that can be defected from cells, stained, and arranged in order from through the CVS (e.g. disjunctions and translocation, largest to smallest so that their number and structure sickle cell anemia, thalassemia, huntington’s disease can be studied under a microscope. A sample peripheral venous blood or scraping of D. AMNIOCENTESIS cells on the buccal membrane is taken Is the of amniotic fluid through the abdominal wall Cells are allowed to grow until they reach metaphase for analysis at the 14th and 16th week of pregnancy Cells are then stained, placed under the microscope Procedure for Amniocentesis then photographed Amniocentesis Chromosomes are identified according to size, Amniotic fluid is located by UTZ shape, and stain ↓ FISH ( Flourescence in situ hybridization) A needle is inserted transabdominally and about 20 ml of Newer method of karyotyping fluid is aspirated It allows karyotyping immediately ↓ Results can be taken in one day Skin cells in the fluid is karyotyped for chromosomal Number and structure B. MATERNAL SERUM SCREENING ↓ ( Maternal Serum Alpha-Fetoprotein) MSAFP AFP AFP is analyzed glycoprotein produced by the fetal liver that reaches a peak in maternal serum/blood between 13th and AMNIOCENTESIS 32nd weeks of pregnancy Has an advantage over CVS of carrying a lesser risk Normal : 10-20mg/ml of spontaneous miscarriage Low: fetal chromosomal disease is present Considerations: RESULT:  Empty the bladder  Fetal spinal cord disease: ↑  The mother should be in left lateral position  Fetal chromosomal diseases: ↓ E. PERCUTANEOUS UMBILICAL BLOOD SAMPLING C. CHORIONIC VILLI SAMPLING PUBS or cordocentesis Is a diagnostic technique that involves retrieval and Removal of blood from the fetal umbilical cord at analysis of the chorionic villi from the growing fetus about 17th weeks of pregnancy using amniocentesis for chromosomes and DNA analysis technique Highly accurate This allows rapid analysis of blood components as Commonly done between 8th and 10th week of well as more rapid karyotyping pregnancy 5 genetic counseling  Maternal AND CHILD HEALTH NURSING LECTURE F. FETAL IMAGING MRI and UTZ Are diagnostic tools used to assess a fetus for general size and structural disorders of internal organs, spine and limbs III. DIAGNOSTIC TESTING G. FETOSCOPY is the insertion of a fiberoptic fetoscope through a small incision in the mothers abdomen into the uterus and membranes to visually inspect the fetus for gross abnormalities IMPORTANT ASPECT OF GENETIC COUNSELLING 1. Results of testing are confidential 2. Respect couples privacy 3. Provide appropriate information and counseling 4. Offer support for them to deal with their feeling 6 genetic counseling