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.
, Exam 7
Ch 4
Genes and Genetic
Down syndrome, Mental retardation, Recessive inheritance, Cystic fibrosis, Transcription,
Nondisjunction, Aneuploidy, Polyploidy, Translocation, Klinefelter syndrome, Turner syndrome,
Cri du chat, Recessive, Dominant traits, Penetrance, Expressivity, Dominance, Recessiveness
*Disorders caused by dominant and recessive traits
1) Specific chromosomal abnormality responsible for Down Syndrome (Ch. 4,
Pg. 144)
● 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 (termed
trisomy). Females have 3-X chromosomes in each cell. Most common
● Trisomy of the twenty-first chromosome is the autosome aneuploidy which causes Down
Syndrome
● The karyotype of down syndrome consists of 47 chromosomes and shows trisomy 21
● Robertsonian translocation involves the fusion of the long arm of chromosome 21 and develops
down syndrome.
2) Causes of mental retardation/intellectual disability (pg 146)
Chromosome abnormalities are the leading know cause of mental retardation.
● About 75% of individuals with spina bifida have secondary hydrocephalus, which sometimes in
turn produces mental retardation.
● Cri du chat Syndrome – disease caused by chromosomal deletion. Means “cry of the cat”
causing intellectual disability. Deletions- broken and loss DNA. Zygote has one chromosome
that’s normal and one with missing genes.
● Fragile X Syndrome – A fragile site (a number of areas on chromosomes develop microscopically
observable breaks and gaps when the cells are cultured in a folate-deficient medium) located on
the long arm of the X chromosome. Fragile X syndrome is the second most common genetic
cause of mental retardation (after Down Syndrome) effecting 1 in 4,000 males and 1 in 8,000
females. Caused by elevated number (>200) of repeated DNA sequences that are duplicated
● Phenylketonuria (PKU) genotype – child unable to metabolize amino acide. Affects infants. If
left untreated, abnormal metabolites of phenylalanine will begin to accumulate in the infant’s
brain and irreversible mental retardation will occur. By imposing dietary restrictions to limit the
intake of food containing phenylalanine, however, retardation can be prevented. Although the
child still has the PKU genotype (genes), a modification of the environment (in this case the
child’s diet) produces an outwardly normal phenotype (genes and environmental factors).
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.
, Exam 7
Ch 4
Genes and Genetic
Down syndrome, Mental retardation, Recessive inheritance, Cystic fibrosis, Transcription,
Nondisjunction, Aneuploidy, Polyploidy, Translocation, Klinefelter syndrome, Turner syndrome,
Cri du chat, Recessive, Dominant traits, Penetrance, Expressivity, Dominance, Recessiveness
*Disorders caused by dominant and recessive traits
1) Specific chromosomal abnormality responsible for Down Syndrome (Ch. 4,
Pg. 144)
● 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 (termed
trisomy). Females have 3-X chromosomes in each cell. Most common
● Trisomy of the twenty-first chromosome is the autosome aneuploidy which causes Down
Syndrome
● The karyotype of down syndrome consists of 47 chromosomes and shows trisomy 21
● Robertsonian translocation involves the fusion of the long arm of chromosome 21 and develops
down syndrome.
2) Causes of mental retardation/intellectual disability (pg 146)
Chromosome abnormalities are the leading know cause of mental retardation.
● About 75% of individuals with spina bifida have secondary hydrocephalus, which sometimes in
turn produces mental retardation.
● Cri du chat Syndrome – disease caused by chromosomal deletion. Means “cry of the cat”
causing intellectual disability. Deletions- broken and loss DNA. Zygote has one chromosome
that’s normal and one with missing genes.
● Fragile X Syndrome – A fragile site (a number of areas on chromosomes develop microscopically
observable breaks and gaps when the cells are cultured in a folate-deficient medium) located on
the long arm of the X chromosome. Fragile X syndrome is the second most common genetic
cause of mental retardation (after Down Syndrome) effecting 1 in 4,000 males and 1 in 8,000
females. Caused by elevated number (>200) of repeated DNA sequences that are duplicated
● Phenylketonuria (PKU) genotype – child unable to metabolize amino acide. Affects infants. If
left untreated, abnormal metabolites of phenylalanine will begin to accumulate in the infant’s
brain and irreversible mental retardation will occur. By imposing dietary restrictions to limit the
intake of food containing phenylalanine, however, retardation can be prevented. Although the
child still has the PKU genotype (genes), a modification of the environment (in this case the
child’s diet) produces an outwardly normal phenotype (genes and environmental factors).
