chapter 7: congenital and genetic disorders pathophysiology ms. harris
TRANSCRIPT
Congenital/Genes
• Congenital= defects or damage to a developing fetus that are present at birth– Genetic abnormalities– Malformation– Chromosomal abnormalities
• Genes- are segments of DNA that code for a specific trait. DNA is what makes up chromosomes.
Chromosomes• Humans have 23 pairs. (23 from egg, 23
from sperm that join together to form the zygote)
• Karyotypes show all pairs – 1-22 = Autosomes– 23rd pair = sex chromosomes
Chromosomal Disorders
• Can be diagnosed by identifying abnormalities on a karyotype.
• Failure of chromosomes to separate in meiosis = non-disjunction (result is either a monosomy or trisomy)
• Translocations, deletions of chromosomes can also occur
Trisomy 21
• More commonly called Down Syndrome
• Causes mental retardation, shortened lifespan, oblique eye, smaller chin
• 1 in 1000 births
Turner’s syndrome
• Malfunctioning ovaries, sterility, heart defects, short stature
• 1 in 2500 female births
Congenital Defects, cont.
• Sometimes, just a single gene is affected.
• Sometimes, they are multifactorial
Congenital Disorders, cont.
• Can be inherited or caused by teratogenic agents– Things that cause damage to the fetus
• Smoke, alcohol, etc.
Punnett Squares
• Used to predict chances for having a child with one of the following types of disorders:– Autosomal dominant, autosomal recessive,
sex-linked dominant, sex-linked recessive
Punnett Square Review
1. Autosomal recessive(ex. Cystic fibrosis)• What are the chances that an affected
female and a normal (homozygous) male will have a child with cystic fibrosis?
Punnett Square Practice
• Autosomal dominant (ex. Huntington’s)– What is the probability that and affected
(heterozygous) parent and a normal parent will have a child born with Huntington’s disease?
Punnett Square Practice
• X- linked disorder (duchenne’s muscular dystrophy)– What is the probability that a carrier female
and a normal male will have a child born with MD?
Multifactorial Disorders
• Lots of things factor into the expression of the disease– Many genes– Environmental factors– Etc.
Developmental Disorders
• Anomalies can be caused by exposure to teratogens.– Mercury, alcohol, many chemicals– First 2 months are the most critical because
cells are differentiating (organogenesis)– Cerebral Palsy
Diagnostic Tools
• Amniocentesis for prenatal diagnosis
• Neonatal blood testing following birth– Most hospitals make several tests mandatory