OB quiz 1
Ob terms
GENETICS AND THE CHILDBEARING FAMILY
Advances in genetics, the study of heredity, and genomics, the study of genes and
... [Show More] their
function and related technology, are providing better methods for:
■ preventing diseases and abnormalities,
■ diagnosing diseases,
■ predicting health risks
■ personalizing treatment plans.
Genes are composed of DNA and protein
Genes are composed of DNA (hereditary material) and protein.
They are the basic functional and physical units of heredity.
There are approximately 30,000 genes in the human genome.
■ The human genome is an organism’s complete set of DNA 30,000 genes.
Numerous genes are located on each human chromosome.
■ Each human cell contains 46 chromosomes.
■ There are 22 homologous pairs of chromosomes and one pair of sex
chromosomes (XX female or XY male ).
Genotype refers to a person’s genetic makeup.
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Phenotype refers to how the genes are outwardly expressed (i.e., eye color, hair
color, height).
Dominant and Recessive Inheritance
Genes are either dominant or recessive. When there is both a dominant and a
recessive gene in the pair, the traits of the dominant gene are present.
The traits of the recessive gene are present when both genes of the pair are
recessive.
CRITICAL COMPONENT
Genetics and Genomics
“The main difference between genomics and genetics is that genetics scrutinizes the functioning and
composition of the single gene whereas genomics addresses all genes and their interrelationships in
order to identify their combined influence on the growth and development of the organism.”
■ Antepartal Period
■ Genetic diseases or disorders are usually related to a defective recessive gene and present
in the developing human when both pairs of the gene have the same defect.
Examples of common recessive genetic disorders are cystic
fibrosis, sickle cell anemia, thalassemia, and Tay-Sachs
disease (Table 3-1).
A person who has only one recessive gene for a disorder is
known as a carrier and does not present with the disorder.
■ Genetic disorders related to a dominant gene are rare. Sex-Linked Inheritance
Also referred to as X-linked inheritance or traits (see Table 3-1)
These are genes or traits that are located only on the
X chromosome. These genes can be either recessive or dominant. The Y chromosome
does not have the corre- sponding genes for some of the X chromosome’s genes.
A male child who receives an X chromosome with a disor- der of one or more of its
genes presents with the disorder when the Y chromosome does not carry that gene;
the gene, even though it may be recessive, becomes dominant.
Female children who have one X chromosome with a sex-linked trait disorder do not
present with the trait, but are carriers of the trait.
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Relevance of Genetics in the Care of the Childbearing Family
■ The scientific knowledge of genetics is rapidly increasing with the desire that gene therapy
will be used to correct genetic disorders such as heart disease, diabetes, and Down
syndrome.
■ The Human Genome Project, a 13-year international, collaborative research program that
was completed in 2003, has provided the scientific community with valuable information
that is being used in the diagno- sis, treatment, and prevention of genetically linked
disorders.
■ 10% of all abnormalities of the developing human are due to genetic factors (Sadler,
2004).
Genetic Testing
There are several genetic tests that are selectively used in the care of the childbearing
families. These include:
Carrier testing
Used to identify individuals who carry one copy of a gene mutation that, when present in two
copies, causes a genetic disorder.
Used when there is a family history of a genetic disorder.
■ When both prospective parents are tested, the test can provide information about
their risk of having a child with a genetic condition.
Preimplantation testing, also known as preimplantation genetic diagnosis (PGD)
■ Used to detect genetic changes in embryos that are
created using assisted reproductive techniques.
Prenatal testing
■ Allows for the early detection of genetic disorders, such as trisomy 21, hemophilia, and TaySachs disease.
Newborn screening
■ Used to detect genetic disorders that can be treated early in life.
Disorders and diseases are related to defective RECESSIVE genes and
generally present at birth on an individual who has a pair of genes with the
same defect on both.
People with one defective gene can carry it and pass it on to their children but
don’t express the trait themselves (autosomal recessive disorders)
TABLE 3–1 GENETIC DISEASES
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SICKLE-CELL ANEMIA (R)- The most common genetic disease among people of African
ancestry. Sickle-cell hemoglobin forms rigid crystals that distort and disrupt red blood cells
(RBCs); oxygen-carrying capacity of the blood is diminished.
CYSTIC FIBROSIS (R)- The most common genetic disease among people of European ancestry.
Production of thick mucus clogs in the bronchial tree and pancreatic ducts. Most severe effects
are chronic respiratory infections and pulmonary failure.
TAY-SACHS DISEASE (R)- The most common genetic disease among people of Jewish
ancestry. Degeneration of neurons and the nervous system results in death by the age of 2 years.
PHENYLKETONURIA OR PKU (R)- Lack of an enzyme to metabolize the amino acid
phenylalanine leads to severe mental and physical retardation. These effects may be prevented by
the use of a diet (beginning at birth) that limits phenylalanine. [Show Less]