Congenital Abnormalities Flashcards
Examples of physical or genetic disorders
- Congenital, physical deformities - Tracheoesophageal Fistula (TEF), cleft lip
- Chromosomal disorders – Down Syndrome
- Gastrointestinal disorders – Omphalocele, Gastroschisis
- Nervous System disorders – spina bifida
- Skeletal disorders – talipes deformities (club foot)
autosomal recessive disorder
An autosomal recessive disorder means two copies of an abnormal gene must be present in order for the disease or trait to develop. Each offspring will have a one-in-four chance of being affected and a two-in-four chance of being a carrier.
Autosomal dominance
Autosomal dominance is a pattern of inheritance characteristic of some genetic diseases.
“Autosomal” means that the gene in question is located on one of the numbered, or non-sex, chromosomes. “Dominant” means that a single copy of the disease-associated mutation is enough to cause the disease.
Y-linked inheritance
Inheritance of genes on the Y chromosome. Since only males normally have a Y chromosome, Y-linked genes can only be transmitted from father to son. Y-linked inheritance is also called holandric inheritance.
What is translocation?
What are two main types?
A translocation is a rearrangement of chromosomes. Sometimes, when cells are dividing during the formation of the egg or the sperm, or in the very early development of the baby, one or more parts of the chromosomes can break off and then rejoin, but in a new location which can be on a different chromosome. This can cause a translocation.
two main types of translocation:
- Reciprocal Translocation - This occurs when two fragments break off from two different chromosomes and “swap places”.
- Robertsonian Translocation - This occurs when two whole chromosomes become “stuck together”.
What kind of gene defect is cystic fibrosis
RECESSIVE.
Must inherit two defective cystic fibrosis genes, one from each parent, to have the disease. Each time two carriers of the disease conceive, there is a 25 percent chance of passing cystic fibrosis to their children ; a 50 percent chance that the child will be a carrier of the cystic fibrosis gene; and a 25 percent chance that the child will be a non-carrier.
Unless both parents have at least one such gene, their children will not have cystic fibrosis. If both parents carry a defective cystic fibrosis gene, each pregnancy has a 25 percent chance of producing a child with cystic fibrosis
Symptoms of cystic fibrosis
People with CF have a variety of symptoms including: very salty-tasting skin; persistent coughing, at times with phlegm; wheezing or shortness of breath; an excessive appetite but poor weight gain; and greasy, bulky stools. Symptoms vary from person to person, in part, due to the more than 1,000 mutations of the CF gene.
Testing for cystic fibrosis
The sweat test: simple and painless procedure measures the amount of salt in the sweat. A high salt level indicates CF. Although the results of this test are valid any time after a baby is 24 hours old, collecting a large enough sweat sample from a baby younger than 3 or 4 weeks old may be difficult.
If pancreatic enzyme levels are reduced, an analysis of the person’s stool may reveal decreased or absent levels of the digestive enzymes (trypsin and chymotrypsin) or high levels of fat.
If insulin secretion is reduced, blood sugar levels are high.
Pulmonary function tests, chest x-ray
During pregnancy, an accurate diagnosis of cystic fibrosis in the fetus is usually possible.
Prognosis for CF
treatments can now postpone some of the changes that occur in the lungs. Half of the people with cystic fibrosis live longer than 28 years. Long-term survival is somewhat better in males, people who don’t have pancreatic problems, and people whose initial symptoms are restricted to the digestive system. Despite their many problems, people with cystic fibrosis usually attend school or work until shortly before death.
According to the CF Foundation’s National Patient Registry, the median age of survival for a person with CF is currently 33.4 years. Only thirty years ago, a CF patient was not expected to reach adulthood. Many people even live into their fifties and sixties. As more advances have been made in the treatment of CF, the number of adults with CF has steadily grown. Today, nearly 40 percent of the CF population is age 18 and older.
Complications of CF
Adults, however, may experience additional health challenges including CF-related diabetes and osteoporosis. CF also can cause reproductive problems - more than 95 percent of men with CF are sterile. But, with new technologies, some are becoming fathers. Although many women with CF are able to conceive, limited lung function and other health factors may make it difficult to carry a child to term.
Down’s syndrome genetics
Down syndrome is the most common chromosomal abnormality, extra chromosome 12 (group G) trisomy 21; Involves the C21 gene; 1:800 live births
Most cases of Down syndrome are not inherited, but occur as random events during the formation of reproductive cells (eggs and sperm). An error in cell division called nondisjunction results in reproductive cells with an abnormal number of chromosomes. For example, an egg or sperm cell may gain an extra copy of chromosome 21. If one of these atypical reproductive cells contributes to the genetic makeup of a child, the child will have an extra chromosome 21 in each of the body’s cells.
three copies of chromosome 21 instead of the usual two copies. Interrupts the normal course of development. Some people who have Down syndrome have an extra number 21 chromosome in only some of their body’s cells. This type of Down syndrome is called mosaic Down syndrome. A small number of individuals have Down syndrome because part of chromosome 21 becomes attached (translocated) to another chromosome before or at the time of conception. These individuals have two copies of chromosome 21, and additional material from chromosome 21 that is attached to another chromosome. The chromosomes of parents of a child with Down syndrome caused by a translocation are studied to see whether the translocation was inherited.
Symptoms of Down’s syndrome
- Low set ears
- Simian crease – an extra fold in the palms of the hands
- Hypotonicity – poor muscle tone; a worry related to breathing as the diaphragm is a muscle
- Protruding tongue – nutritional issues present (maybe)
- Back of the head will be flat
- Short, thick fingers
- More frequent occurrence of ALL (acute lymphocytic leukemia)
- Cardiac anomalies
- Early intervention necessary for a good outcome!
Turner syndrome genetics
chromosomal condition.
affects development in females.
Most cases are not inherited. When this condition results from monosomy X, the chromosomal abnormality occurs as a random event during the formation of reproductive cells in the affected person’s parent. An error in cell division called nondisjunction can result in reproductive cells with an abnormal number of chromosomes. For example, an egg or sperm cell may lose a sex chromosome as a result of nondisjunction. If one of these atypical reproductive cells contributes to the genetic makeup of a child, the child will have a single X chromosome in each cell and will be missing the other sex chromosome.
Turner syndrome characteristics
Most common feature is short stature, becomes evident by about age 5.
Early loss of ovarian function (ovarian hypofunction or premature ovarian failure) ovaries develop normally at first, but egg cells (oocytes) usually die prematurely and most ovarian tissue degenerates before birth.
Many do not undergo puberty unless they receive hormone therapy, and most are unable to conceive (infertile).
30 percent have extra folds of skin on the neck (webbed neck), low hairline at the back of the neck, puffiness or swelling (lymphedema) of hands and feet, skeletal abnormalities, or kidney problems.
One third to one half are born with a heart defect, such as a narrowing of the large artery leaving the heart (coarctation of the aorta) or abnormalities of the valve that connects the aorta with the heart (the aortic valve). Complications associated with these heart defects can be life-threatening. Most girls and women have normal intelligence.
Developmental delays, nonverbal learning disabilities, and behavioral problems are possible, although these characteristics vary among affected individuals.
Fragile X syndrome genetics
Caused by a “fragile” site at the end of the long arm of the X-chromosome. Although it is an X-linked recessive trait with variable expression and incomplete penetrance, 30% of all carrier women are affected.
Genetic mutation which varies considerably in severity among patients. Fragile X syndrome is the most common cause of inherited mental retardation.
Genetic disorder that manifests itself through a complex range of behavioral and cognitive phenotypes.
Hemophilia
hereditary bleeding disorder, partial or total lack of an essential blood clotting factor. excessive bleeding, and many times spontaneous bleeding, very often, is internal.
Sex-linked recessive disorder, greater prominence in males.
Difference between hemophilia A and B
Hemophilia A is the most common form (classical hemophilia.) result of a deficiency in clotting factor 8.
hemophilia B (Christmas disease) :deficiency in clotting factor 9.
Diagnosis/ prognosis of hemophilia:
Blood tests the presence of hemophilia and whether it is a type A or a type B.
Usually, infants do not show signs before 9 months of age.
Administration of clotting factors help people live with disease.
The prospects for children with hemophilia are excellent. Only a few decades ago, children with hemophilia had a significantly reduced life expectancy. They were often crippled with arthritis and joint deformity by their teens and had to attend special schools for disabled people. Children with hemophilia now face few limitations.
List examples of chromosome disorders,dominant genetic disorders, recessive disorders, sex-linked disorders and genetic predisposition.
CHROMOSOME DISORDERS
• Down syndrome
• Klinefelter’s syndrome
• Turner’s syndrome
DOMINANT GENETIC DISORDERS
• Huntington’s disease
• Polydactyly
• Marfan Syndrome
RECESSIVE GENETIC DISORDERS • Sickle cell anemia • Tay-Sachs • Cystic Fibrosis • PKU
SEX-LINKED GENETIC DISORDERS
• Hemophilia
• Red-green color blindness
• Duchenne muscular dystrophy
GENETIC PREDISPOSITION • Cleft lip/palate • Clubfoot • Spina Bifida • Hydrocephalus • Hypertension • High Cholesterol • Mental Illness • Congenital heart defects • Diabetes Mellitis
Duchenne’s muscular dystrophy
Approximately 1 of every 3,500 males. Classically, DMD is a single gene, X-linked recessive disease, but many cases of DMD are caused by spontaneous genetic mutations.
Genetic defect: inability to produce the protein, dystrophin, which is essential for maintaining health of muscle tissue. Slowly cells of muscles are replaced by fat cells.
Initially, the long muscles of the legs and the muscles in the pelvic area are affected, but eventually all muscle is replaced by fat, including muscles of respiratory and cardiac systems.
Characteristically, the fatal illness ends in death from respiratory infection or cardiac failure when the men reach their late teens or early twenties. The growth of children with DMD usually are within normal limits for first few years of life. At approximately age 3, gross motor development stalls and begins to decline. gross motor skills become more and more difficult, and the child develops:
i. Lordosis (concave curvature of the back, commonly called sway back).
ii. Waddling gait.
iii. Gower’s sign: need to push to standing position by holding onto furniture or using hands to “walk up” the body. Usually seen during the school-age period.
iv. By the time the children become teenagers, they usually are wheelchair bound.
