Guided Lecture Notes
Chapter 4: Genetic and Congenital Disorders
Learning Objective 1. Define the terms congenital, allele, gene locus, gene mutation,
genotype, phenotype, homozygous, heterozygous, polymorphism, gene penetrance, and
gene expression.

Define the term congenital and discuss the incidence and mortality rates of birth
defects.

Using examples from Chapter 3, review the definitions of allele, gene locus
(location), mutation, phenotype, genotype, homozygous, heterozygous, and
polymorphism (refer to PowerPoint Slide 3).

Review the definitions of gene penetrance and gene expression using examples of
autosomal dominant disorders.
Learning Objective 2. Describe three types of single-gene disorder and give an example
of a syndrome, condition, or disorder that would be associated with each type.

Discuss the cause of single-gene disorders and explain the pattern of transmission
(refer to PowerPoint Slide 8).

Explain autosomal dominant disorders and describe the typical pattern of gene
penetrance and gene expression (refer to PowerPoint Slide 7 and Fig. 4-1).

Describe the pathology, clinical presentation, and prognosis associated with
Marfan syndrome (refer to Fig. 4-2).

Identify the genetic presentation of autosomal recessive disorders, and contrast
their pathology with autosomal dominant disorders (refer to Fig. 4-4).

Describe the pathology, clinical presentation, and prognosis associated with TaySachs disease.

Describe the inheritance pattern of X-linked chromosomal disorders (refer to
PowerPoint Slide 13 and Fig. 4-5).

Describe the pathology, clinical presentation, and prognosis associated with
Fragile X syndrome (refer to Fig. 4-6).
Learning Objective 3. Define and give an example of a multifactorial inheritance
disorder.

Identify the causes of multifactorial inheritance disorders, and give examples.

Compare the inheritance patterns of multifactorial inheritance disorders with
single-gene disorders.

Describe the incidence, pathology, and treatment of cleft lip and cleft palate.
Learning Objective 4. Differentiate between mitochondrial and nuclear genes in regard
to DNA content.

Explain the differences between mitochondrial and nuclear DNA (refer to
PowerPoint Slide 14).

Describe the inheritance pattern of mitochondrial DNA.

Compare the incidence of disorders of mitochondrial and nuclear DNA.
Learning Objective 5. Discuss three types of chromosomal disorders utilizing key
terms.

Describe the incidence of chromosomal disorders.

Explain how chromosomal disorders are commonly described.

Using examples, explain the cause of alterations in chromosome structure.

Define the terms deletion, inversion, ring formation, and translocation as they
relate to structural abnormalities of the chromosome (refer to PowerPoint Slide
15).

Using examples, explain the cause of alterations in chromosome duplication.

Describe mosaicism (refer to PowerPoint Slide 18).

Using examples, explain the cause of alterations in chromosome number.

Define the terms aneuploidy, nondisjunction, monosomy, and polysomy as they
relate to alterations in the number of chromosomes.
Learning Objective 6. Describe three patterns of chromosomal breakage and
rearrangement (refer to Fig. 4-8).

Using examples, explain deletion, inversion, ring formation, and translocation as
they relate to structural abnormalities of the chromosome (refer to PowerPoint
Slide 15).

Identify the pattern of breakage that is the least likely to result in an abnormality,
and explain why.
Learning Objective 7. Describe two chromosomal abnormalities that demonstrate
aneuploidy.

Using examples, explain monosomy (refer to PowerPoint Slide 18).

Using examples, explain polysomy (refer to PowerPoint Slide 18).

Compare the severity of disorders caused by monosomy and polysomy.
Learning Objective 8. Relate maternal age and occurrence of Down syndrome.

Discuss the incidence of Down syndrome.

Explain how advanced maternal age increases the incidence of Down syndrome,
citing the numerical risk.

Discuss the possible cause of increased incidence of Down syndrome with
advanced maternal age.
Learning Objective 9. Cite the most susceptible period of intrauterine life for
development of defects due to environmental agents.

Identify the period of development where the embryo is at the greatest risk for
developmental defects.

Discuss the effects of environmental influences on the developing embryo (refer
to PowerPoint Slide 19).

Identify the time period when each organ is most susceptible to environmental
influences (refer to Fig. 4-11).
Learning Objective 10. State the cautions that should be observed when considering the
use of drugs during pregnancy.

List common drugs that are considered harmful to the developing embryo (refer to
Chart 4-1).

Identify the stage of development in which the embryo is most susceptible to
teratogens.

Explain the mechanism by which drugs cause damage to the embryo, and identify
the factors that affect placental drug transfer.

Describe the FDA classification of drugs according to probable risk to the fetus.
Learning Objective 11. Describe the effects of alcohol abuse on fetal development and
birth outcomes.

Describe the incidence of fetal alcohol syndrome (FAS).

Describe the variable effects of alcohol on fetal development.

Explain the purpose of the National Task Force on Fetal Alcohol Syndrome and
Fetal Alcohol Effects.

Explain how a diagnosis of FAS is made.

Discuss the clinical presentation of children afflicted with FAS (refer to Fig. 412).
Learning Objective 12. Define TORCH and discuss its importance in regards to
congenital malformations.

Identify the list of microbes that comprise the acronym TORCH.

Describe the clinical manifestations associated with TORCH.

Discuss ways in which expectant mothers can reduce the likelihood of contracting
an infectious disease.
Learning Objective 13. Define AFP as a maternal serum marker, and state its role in the
diagnosis of potential neural tube defects.

Explain what AFP is and when it peaks in the fetus and the maternal serum.

Explain why AFP levels are elevated when the fetus has a neural tube or ventral
wall defect.

Identify the gestational period when maternal blood samples are typically
screened for AFP levels.