Study Guide Questions Ch 5

Question 1

In which of the following Mendelian disorders is the age of onset delayed and the symptoms of the disease do not appear before adulthood?

a. Huntington’s disease
b. Parkinsons disease
c. Fanconi syndrome
d. Down Syndrome
e. Fragile X syndrome

Answer 1

A

Huntington’s disease

Question 2

Which of the following diseases is caused by a trinucleotide repeat mutation?

a. Marfan syndrome
b. Achondroplastic dwarfism
c. Fanconi syndrome
d. Fragile X syndrome
e. Hemophilia B

Answer 2

D,

Fragile X syndrome is caused by a trinucleotide repeat mutation of the long arm of the X chromosome. Patients with the disease present with mental retardation and enlarged testes.

Question 3

Type V glycogenosis, also known as McArdle disease, is caused by _______ deficiency.

a. muscle phosphorylase
b. glycogen
c. protein C
d. hemoglobin

Answer 3

a. muscle phosphorylase

Patients present with muscle cramps. In these patients, the blood level of lactic acid does not rise after exercise, because the enzyme deficiency prevents anaerobic glycolysis in the muscle cells.

Question 4

Lysyl hydroxylase is an enzyme that is essential for cross-linking of ____.

a. Collagen
b. Fibrin
c. Actin
d. Tubulin

Answer 4

a. collagen

Without it, the collagen never achieves full structural integrity and strength; accordingly, the
bones are weak and prone to deformation, whereas the skin becomes hyperextensible
(“cutis laxa”).

Question 5

Children with Down syndrome are at a 10 to 20-fold higher risk of developing ______ or _____ than are their age-matched controls.

Answer 5

acute lymphoblastic leukemia

acute myelogenous leukemia

Question 6

Gaucher disease is caused by a mutation of the gene encoding ______.

a. phosphorylase
b. glucocerebrosidase
c. enterokinase

Answer 6

b. glucocerebrosidase

In the most common of the three forms of Gaucher disease, which accounts for 99% of all
cases, there is splenomegaly, lymphadenopathy, involvement of the bone marrow, and
skeletal changes.

Question 7

An infertile woman was examined cytogenetically and was found to have deletions ofportions of the long arm and short arm of the chromosome X, resulting in a ringchromosome, 46,X,r(X). Which of the following is the most likely diagnosis?

a. Klinefelter syndrome
b. Turner syndrome
c. Fanconi syndrome
d. Fragile X syndrome
e. Hemophilia B

Answer 7

B, Turner Syndrome

Question 8

Chromosome 22q11 deletion is typically associated with

a. rocker-bottom feet
b. horseshoe kidneys
c. thymic hypoplasia
d. microphthalmia
e. simian crease on hands

Answer 8

C.

Chromosome 22q11 deletion is found in children who have DiGeorge syndrome and velocardiofacial syndrome. These two syndromes are known to be closely related and are known as the CATCH 22 syndrome (cardiac abnormalities, anomalous facial features, thymic hypoplasia with T-cell deficiencies, cleft palate, and hypocalcemia due to hypoparathyroidism resulting from chromosome 22q11 deletion).