Chapter 7:Congenital and

Genetic Disorders

Pathophysiology

Ms. Harris

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

Normal female

Normal male

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

Can you spot the abnormality?

Trisomy 21

• More commonly called Down Syndrome

• Causes mental retardation, shortened lifespan, oblique eye, smaller chin

• 1 in 1000 births

Can you spot the abnormality?

Turner’s syndrome

• Malfunctioning ovaries, sterility, heart defects, short stature

• 1 in 2500 female births

Can you spot the abnormality?

Can you spot the abnormality?

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?

Pedigree Practice

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

Gene therapy

Current Event Analysis:

1. Name 3 cause/effects from the article.

2. Make a T-chart to list pros and cons of gene therapy. (think beyond the article!)