Genetic Assessment & Counseling
Genetic Assessment
 The possibility that a child could have a genetic disorder is always present.
 Nurses can stress the importance of the national genome program and
supporting families during genetic testing.
 Nurse is the educator, supporter and communicator for the family.
 Nursing Process:
 Assess, Plan, Implement, and Evaluation
Genetic Disorders
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Inherited or genetic disorders are disorders that can be passed from one
generation to the next.
They result from some disorders in gene or chromosome structure.
Genetics-is the study of the way such disorders occur.
Abnormalities can occur at ovum and sperm fusion or earlier, in meiotic
division phase.
50% of 1st trimester spontaneous miscarriage
may be due to chromosomal abnormalities.
Nature of Inheritance
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Genes-basic unit of heredity that determines both physical and mental
characteristics of people.
 Composed of segments of DNA, they direct protein synthesis.
 Woven into strands in the nucleus of all body cells to form chromosomes.
 44 autosomes and 2 sex chromosomes
 alleles-two like genes
 phenotype-outward appearance or the expression of the genes
 Genotype- actual gene composition
 Genome-complete set of genes present (50,000 to 100,000)
Dominant and Recessive Patterns:
Homozygous-two like genes for a trait on two like chromosomes.
Heterozygous-genes are different
Dominant genes-dominant in their action over other when paired with other
genes.
Dominant and Recessive Patterns
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Recessive-gene is not dominant.
Mendelian laws permit the prediction of inheritance of traits.
 eye color
 disorders
Example:
 father homozygous dominant for brown eyes
 mother homozygous recessive for blue eyes
 100% chance for brown eyes (phenotype)
 carry a recessive gene for blue eyes (genotype)
Inheritance of Disease
 Autosomal Dominant Disorders:
 over 1000 autosomal disorders
 person with a dominant gene for a disease is usually heterozygous (has a
corresponding healthy recessive gene for the trait)
 Huntington disease-specific gene on chromosome 4
 If 2 people with a dominantly inherited disorder; 25% chance of the child
being disease free and carrier free
 50% will have the disorder
 25% chance homozygous dominant and incompatible with life.
 1. One parent of child with the disorder will also have the disorder.
 2. Sex is unimportant
 3. Usually a history of disorder in other family members
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Autosomal Recessive Inheritance:
Most genetic disorders are inherited as recessive not dominant traits.
Inborn errors of metabolism
 cystic fibrosis, Tay-Sachs disease, Rh-factor
1. Both parents free of the disorder
2. Sex unimportant
3. Family history is negative
4. Common ancestor exists
X-Linked Dominant Inheritance:
Transmitted only by the female sex chromosome.
1. All individuals with the gene are affected.
2. Female children of affected men are all infected.
3. Appears in every generation.
4. All children of homozygous affected women are affected. 50% of
heterozygous affected women are affected.
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X-Linked Recessive Inheritance:
Majority of X-Linked disorders are recessive.
Mother is the carrier.
If paired with another X (female) the disease is blocked.
If gene not paired (male) the disease will manifest.
 Hemophilia A, color blindness, muscular dystrophy
Imprinting-differential expression of genetic material and allows researchers to
identify if it has come form male or female.
Genetic marker-specific point on a chromosome that marks the location of
missing or abnormal gene.
Meiosis-cell division which the number of chromosomes in cell is reduced to
1/2 for reproduction (23)
Genetic Counseling
 Anyone concerned should have access.
 Ideal time before 1st pregnancy especially if a familial disorder is present.
 Couple with a child who has a genetic disorder.
 Nursing responsibility:
 concrete information
 informed choices
 educate
 offer support
Assessment for Genetic Disorder
 History: Family history
 Mothers age
 Ethnic background
 Spontaneous abortions or death at birth
 Prenatal environmental conditions
 Physical Assessment:
 Dermatoglyphics (study of surface markings of skin-webbing, digits, hair
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Diagnostic testing:
Karyotyping-visual presentation of the chromosome pattern of an individual.
Barr body determination-evaluates if child has 2 X chromosomes.
Alpha-fetoprotein analysis-glycoprotein produced by the fetal liver.
 Spinal cord disorder
Chorionic villi sampling-retrieval and analysis of chorionic villi.
Amniocentesis:
Withdrawal of amniotic fluid through the abdominal wall for analysis at the
14th to 16th week of pregnancy.
Percutaneous umbilical blood sampling:
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PUBS-removal of blood from umbilical cord using amniocentesis.
Sonography:
assesses a fetus for size, structural disorders (organs, spine and limbs).
Fetoscopy:
insertion of a fiberoptic fetoscope through a small incision in the mother’s
abdomen into the uterus and membranes to inspect the fetus for gross
abnormalities.
Legal and ethical aspects:
The choice to be made is the couple’s not the counselor’s.
Common Chromosomal Disorders
 Trisomy 13 Syndrome: (Patau Syndrome)
 extra chromosome 13
 severely cognitively challenged
 0.45 per 1000 live births
 midline body disorders
 microcephaly with abnormalities of the forebrain and forehead.
 eyes that are smaller than normal or absent
 cleft lip and palate
 low set ears, heart defects, particularly ventricular septal defects and
abnormal genitalia.
 most do not survive beyond early childhood.
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Trisomy 18 Syndrome:
3 number 18 chromosomes
severely cognitively challenged
0.23 per 1000 live births
small for gestational age at birth
Markedly low-set ears, small jaw, congenital heart defects, misshapen fingers
and toes (index finger cross over others), soles of feet rounded instead of flat(
rocker-bottom feet).
most do not survive beyond early infancy
Cri-du-Chat Syndrome:
missing portion of chromosome 5
abnormal cry (sounds like a cat)
small head, wide set eyes, downward slant to the palpebral fissure of the eye.
Turner Syndrome:
gonadal dygenesis; 45XO
has only one functional X chromosome
short in stature, hair line at nap of neck low-set, neck appears webbed and
short, edema of hands and feet.
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Congenital anomalies-coarctation of the aorta, kidney disorders, small nonfunctioning gonads, except pubic hair secondary sex characteristics do not
develop at puberty, sterility, cognitive
impairment, stunted height growth
may be given estrogen at age 13
Klinefelter Syndrome:
males with XXY chromosome pattern (47XXY)
not noticeable at birth
at puberty poorly developed secondary sex characteristics, small testes,
gynecomastia
1 per 1000 live births
karyotyping may reveal additional X
Fragile X Syndrome:
X-linked pattern; one arm of X chromosome is defective
most common cause of cognitive challenge in boys
1 in 1000 live births
before puberty- hyperactivity, autism, deficits in speech and arithmetic,large
head and protruding ears, long face with high forehead, prominent lower jaw,
enlarge testicles after puberty.
Hyperextensive joints, cardiac disorders
female carriers may show some evidence of physical and cognitive
characteristics.
Down Syndrome (Trisomy 21):
most frequent chromosomal abnormality
1 in 800 live births
most frequently occurs in pregnancies of women over 35 (1 in 100 live births).
Paternal age over 55 also
Low AFP
Physical features:
nose is broad and flat, eyelids have extra fold of tissue at inner canthus and
palpebral fissure tends to slant upward, iris has white specks in it (Brushield
spots), oral cavity is small and tongue protrudes, back of head is flat and neck
is short, extra pad of fat at base of head, ears are low-set, muscle tone is
poor, fingers short and thick, little finger curved inward, wide space between
1st and 2nd toes and fingers, palm of hand shows
a peculiar crease or horizontal palm crease instead of 3 creases.
cognitive impairment (IQ 50-70), altered immune function-prone to respiratory
infections, congenital heart disease-AV defect, stenosis or atresia of
duodenum, strabismus and cataracts, acute lymphocytic leukemia 20 times
more frequently.
life span 40 to 50 years