NU 545
Unit 7 Study Guide
Advanced Pathophysiology
University of South Alabama.
This document provides a focused
study guide
It summarizes key concepts, lecture highlights, and
exam-relevant material to support efficient last-minute
review. The guide is structured to help students
reinforce understanding, identify weak areas, and prepare
confidently for the assessment.
,Unit 7: Genes, Genetic Disease, Disorders of
the Integument, Shock, Burns, Tumors, and
Cancer
NU545: Physio-Pathological Basis of Advanced Nursing
Study Guide: Chapters 4–6, 12–14, & 46–49; McCance and
Huether, 7th edition
Edited by: Jessica L. Santos
,SECTION I: STUDY GUIDE
1. Describe the specific chromosomal abnormality responsible for Down syndrome
(pp. 145-147; key search term: “example of aneuploidy”)
Aneuploid cells are defined as those that do not contain a multiple of 23 chromosomes. An
aneuploid cell containing 3 copies of one chromosome is said to be trisomic (condition called
trisomy). Newborns with trisomy of chromosomes 13, 18, or 21 can survive. The most well-
known example of aneuploidy in an autosome is trisomy of the 21st chromosome, which
causes Down syndrome. One of the most common is trisomy X. About ¾ of infants born with
Down syndrome die during their first 10 years of life. For those that survive, life expectancy is
60 years.
Aneuploidy is usually the result of nondisjunction, an error in which homologous
chromosomes or sister chromatids fail to separate normally during meiosis or mitosis. 97% of
Down syndrome cases are caused by nondisjunction during the formation of one of the
parents’ gametes or during early embryonic development, and the remaining 3% by
translocations. In 95%, the nondisjunction occurs in the formation of the mother’s egg cell.
About 1% have mosaics in which large numbers of normal cells are present, causing less
effects of trisomic cells and are attenuated.
The risk of having a child with Down syndrome increases with maternal age.
2. Causes of mental retardation. (pp. 143-151; key search term: “major
chromosome”)
Chromosome abnormalities are the leading known cause of mental retardation and
miscarriage. A major chromosome aberration occurs in more than half of conception. Most of
these fetuses do not survive to term; about 50% of all recovered first-trimester spontaneous
abortions have major chromosomal aberrations. Approximately 1 in 150 live births has a
major diagnosable chromosomal abnormality.
Examples: Aneuploidy (cells that do not contain a multiple of 32 chromosomes; i.e., Down
syndrome, Turner Syndrome, Klinefelter syndrome). Chromosome breakage – deletions:
broken chromosomes and loss of DNA; usually a gamete with a deletion unite with a normal
gamete to form a zygote, thus one zygote has one chromosome with a normal complement of
genes and one with some missing genes (cri du chat syndrome or “cry of the cat” or cry of the
affected child). Translocations: interchanging of genetic material between nonhomologous
chromosomes (Robertsonian translocation) Fragile sites: A number of areas on chromosomes
2
, develop microscopically observable breaks and gaps when the cells are cultured. Example:
fragile X syndrome, which is associated with substantial cognitive impairment (second most
common genetic cause of mental retardation after Down syndrome).
Examples include:
Polyploidy (which is when a euploid cell has more than the diploid number of chromosomes
—includes triploidy which is 3 copies of each chromosome and tetraploidy—4 copies) and
Aneuploidy (do not contain a multiple of 23 chromosomes—includes monosomy which is
the presence of only one copy of a given chromosome, and trisomy which is 3 copies of one
chromosome).
Examples of chromosome abnormalities that lead to mental retardation are: Down syndrome
(1st most common cause), trisomy X 3 or more chromosomes, cri du chat syndrome, fragile X
syndrome (2nd most common cause), Klinefelter syndrome, untreated phenylketonuria (PKU),
Wilms tumor, Angeliman syndrome, and 75% of people with spina bifida.
3. What gene abnormality causes cystic fibrosis? (pp. 154-155, 1310; key search
term: “common lethal recessive”)
CF is an autosomal recessive inherited disease characterized by delayed age of onset,
incomplete penetrance, and variable expressivity.
The CF gene, cystic fibrosis transmembrane conductance regulator gene (CFTCR), is
located on the long arm of chromosome 7 which encodes the protein transmembrane
conductance regulator that functions as a chloride channel and is regulated by cyclic
adenosine monophosphate (cAMP) in the membranes of specialized epithelial cells. Mutation
results in abnormal expression of CFTCR and is associated with defective epithelial chloride
ion transport which leads to a salt imbalance that results in secretions of abnormally thick,
dehydrated mucus. There are more than 1900 known mutations of this gene divided into 6
classes with varying severity of disease expression.
It is the most common lethal autosomal recessive disease in white children and
approximately 1 in 25 whites carries one copy of an allele that can cause CF.
4. How is a recessive disease inherited? (pp. 151, 154-156; key search term: “hiding
in carriers”)
Most recessive disease-causing alleles occur in heterozygotes (genes are not identical at
the locus – the position along a chromosome that each gene occupies) who carry one copy of
the allele but do not express the disease. Because many recessive genes are lethal in the
homozygous (genes are identical at the locus) state, they are eliminated from the population
when they occur in homozygotes. By “hiding” in carriers, however, most recessive genes for
diseases survive to be passed on to the next generation. The number of carriers for recessive
diseases can be high, but recessive diseases are rare. The most common lethal recessive
disease in white children is cystic fibrosis. Because an individual must be homozygous for a
recessive allele to express the disease, the carriers are phenotypically normal. Because most
recessive alleles are maintained in normal carriers, they are able to survive in the population
from one generation to the next. As with many autosomal dominant diseases, many
autosomal recessive diseases are characterized by delayed age of onset, incomplete
penetrance, and variable expressivity.
Important criteria for discerning autosomal recessive inheritance include the following:
1. Males and females are affected in equal proportions.
2. Consanguinity (marriage between related individuals) is often present.
3. The disease is seen in siblings but usually not in their parents.
4. On the average, ¼ of the offspring of carrier parents will be affected.
In most cases of recessive disease, both parents of affected individuals are
heterozygous carriers. On the average, one fourth of their offspring will be normal
3
Unit 7 Study Guide
Advanced Pathophysiology
University of South Alabama.
This document provides a focused
study guide
It summarizes key concepts, lecture highlights, and
exam-relevant material to support efficient last-minute
review. The guide is structured to help students
reinforce understanding, identify weak areas, and prepare
confidently for the assessment.
,Unit 7: Genes, Genetic Disease, Disorders of
the Integument, Shock, Burns, Tumors, and
Cancer
NU545: Physio-Pathological Basis of Advanced Nursing
Study Guide: Chapters 4–6, 12–14, & 46–49; McCance and
Huether, 7th edition
Edited by: Jessica L. Santos
,SECTION I: STUDY GUIDE
1. Describe the specific chromosomal abnormality responsible for Down syndrome
(pp. 145-147; key search term: “example of aneuploidy”)
Aneuploid cells are defined as those that do not contain a multiple of 23 chromosomes. An
aneuploid cell containing 3 copies of one chromosome is said to be trisomic (condition called
trisomy). Newborns with trisomy of chromosomes 13, 18, or 21 can survive. The most well-
known example of aneuploidy in an autosome is trisomy of the 21st chromosome, which
causes Down syndrome. One of the most common is trisomy X. About ¾ of infants born with
Down syndrome die during their first 10 years of life. For those that survive, life expectancy is
60 years.
Aneuploidy is usually the result of nondisjunction, an error in which homologous
chromosomes or sister chromatids fail to separate normally during meiosis or mitosis. 97% of
Down syndrome cases are caused by nondisjunction during the formation of one of the
parents’ gametes or during early embryonic development, and the remaining 3% by
translocations. In 95%, the nondisjunction occurs in the formation of the mother’s egg cell.
About 1% have mosaics in which large numbers of normal cells are present, causing less
effects of trisomic cells and are attenuated.
The risk of having a child with Down syndrome increases with maternal age.
2. Causes of mental retardation. (pp. 143-151; key search term: “major
chromosome”)
Chromosome abnormalities are the leading known cause of mental retardation and
miscarriage. A major chromosome aberration occurs in more than half of conception. Most of
these fetuses do not survive to term; about 50% of all recovered first-trimester spontaneous
abortions have major chromosomal aberrations. Approximately 1 in 150 live births has a
major diagnosable chromosomal abnormality.
Examples: Aneuploidy (cells that do not contain a multiple of 32 chromosomes; i.e., Down
syndrome, Turner Syndrome, Klinefelter syndrome). Chromosome breakage – deletions:
broken chromosomes and loss of DNA; usually a gamete with a deletion unite with a normal
gamete to form a zygote, thus one zygote has one chromosome with a normal complement of
genes and one with some missing genes (cri du chat syndrome or “cry of the cat” or cry of the
affected child). Translocations: interchanging of genetic material between nonhomologous
chromosomes (Robertsonian translocation) Fragile sites: A number of areas on chromosomes
2
, develop microscopically observable breaks and gaps when the cells are cultured. Example:
fragile X syndrome, which is associated with substantial cognitive impairment (second most
common genetic cause of mental retardation after Down syndrome).
Examples include:
Polyploidy (which is when a euploid cell has more than the diploid number of chromosomes
—includes triploidy which is 3 copies of each chromosome and tetraploidy—4 copies) and
Aneuploidy (do not contain a multiple of 23 chromosomes—includes monosomy which is
the presence of only one copy of a given chromosome, and trisomy which is 3 copies of one
chromosome).
Examples of chromosome abnormalities that lead to mental retardation are: Down syndrome
(1st most common cause), trisomy X 3 or more chromosomes, cri du chat syndrome, fragile X
syndrome (2nd most common cause), Klinefelter syndrome, untreated phenylketonuria (PKU),
Wilms tumor, Angeliman syndrome, and 75% of people with spina bifida.
3. What gene abnormality causes cystic fibrosis? (pp. 154-155, 1310; key search
term: “common lethal recessive”)
CF is an autosomal recessive inherited disease characterized by delayed age of onset,
incomplete penetrance, and variable expressivity.
The CF gene, cystic fibrosis transmembrane conductance regulator gene (CFTCR), is
located on the long arm of chromosome 7 which encodes the protein transmembrane
conductance regulator that functions as a chloride channel and is regulated by cyclic
adenosine monophosphate (cAMP) in the membranes of specialized epithelial cells. Mutation
results in abnormal expression of CFTCR and is associated with defective epithelial chloride
ion transport which leads to a salt imbalance that results in secretions of abnormally thick,
dehydrated mucus. There are more than 1900 known mutations of this gene divided into 6
classes with varying severity of disease expression.
It is the most common lethal autosomal recessive disease in white children and
approximately 1 in 25 whites carries one copy of an allele that can cause CF.
4. How is a recessive disease inherited? (pp. 151, 154-156; key search term: “hiding
in carriers”)
Most recessive disease-causing alleles occur in heterozygotes (genes are not identical at
the locus – the position along a chromosome that each gene occupies) who carry one copy of
the allele but do not express the disease. Because many recessive genes are lethal in the
homozygous (genes are identical at the locus) state, they are eliminated from the population
when they occur in homozygotes. By “hiding” in carriers, however, most recessive genes for
diseases survive to be passed on to the next generation. The number of carriers for recessive
diseases can be high, but recessive diseases are rare. The most common lethal recessive
disease in white children is cystic fibrosis. Because an individual must be homozygous for a
recessive allele to express the disease, the carriers are phenotypically normal. Because most
recessive alleles are maintained in normal carriers, they are able to survive in the population
from one generation to the next. As with many autosomal dominant diseases, many
autosomal recessive diseases are characterized by delayed age of onset, incomplete
penetrance, and variable expressivity.
Important criteria for discerning autosomal recessive inheritance include the following:
1. Males and females are affected in equal proportions.
2. Consanguinity (marriage between related individuals) is often present.
3. The disease is seen in siblings but usually not in their parents.
4. On the average, ¼ of the offspring of carrier parents will be affected.
In most cases of recessive disease, both parents of affected individuals are
heterozygous carriers. On the average, one fourth of their offspring will be normal
3
