Chapter 02: Genes and Genetic Diseases
Huether: Understanding Pathophysiology, First Canadian Edition
MULTIPLE CHOICE
1. A nurse recalls that the basic components of DNA are:
a. pentose sugars and four phosphate base
...
Chapter 02: Genes and Genetic Diseases
Huether: Understanding Pathophysiology, First Canadian Edition
MULTIPLE CHOICE
1. A nurse recalls that the basic components of DNA are:
a. pentose sugars and four phosphate bases.
b. a phosphate molecule, deoxyribose, and four nitrogenous bases.
c. adenine, guanine, and purine.
d. codons, oxygen, and cytosine.
ANS: B
The three basic components of DNA are deoxyribose; a phosphate molecule; and four
types of nitrogenous, not phosphate, bases. DNA does not contain condone.
REF: p. 38
2. Which of the following mutations have the most significant effect on protein synthesis?
a. Base pair substitutions
b. Silent mutations
c. Intron mutations
d. Frameshift mutations
ANS: D
The frameshift mutation involves the insertion or deletion of one or more base pairs of the
DNA molecule. This greatly alters the amino acid sequence, which affects protein
synthesis. The base pair substitution is a type of mutation in which one base pair replaces
another. Silent mutations do not change amino acids or protein synthesis. Intron mutations
are part of RNA sequencing.
REF: p. 39
3. The base components of DNA are:
a. A, G, C, and U.
b. P, G, C, and T.
c. A, G, C, and T.
d. X, XX, XY, and YY.
ANS: C
The four base components of DNA are cytosine, thymine, adenine, and guanine, and they
are commonly represented by their first letters (C, T, A, and G). There are no genetic
components identified as P or U. The letters X, XX, XY, and YY are components of
human chromosomes.
REF: p. 38
4. A DNA strand has a region with the sequence ATCGGAT. Which of the following would
be a complementary strand?
a. CGATACGT
b. TAGCCTAG
c. TUGCCTUG
d. UAGCCUAG
ANS: B
The consistent pairing of adenine with thymine and of guanine with cytosine is known as
complementary base pairing; thus, A complements to T and C to G and vice versa
throughout the strand. A complements to T; thus, the first letter must be a T. U does not
represent a complement in the sequence.
REF: p. 39
5. A biologist is explaining how RNA directs the synthesis of protein. Which process is the
biologist describing?
a. Termination
b. Transcription
c. Translocation
d. Translation
ANS: D
In translation, RNA directs the synthesis of a polypeptide, interacting with transfer RNA
(tRNA), a cloverleaf-shaped strand of about 80 nucleotides. Termination does not involve
the synthesis of protein. Transcription is the process by which DNA specifies a sequence
of messenger RNA (mRNA). Translocation is the interchange of genetic material between
nonhomologous chromosomes.
REF: p. 42
6. What is the result of homologous chromosomes failing to separate during meiosis?
a. Neurofibromatosis
b. Aneuploidy
c. Polyploidy
d. Conjoined twins
ANS: B
Nondisjunction is an error in which homologous chromosomes or sister chromatids fail to
separate normally during meiosis or mitosis. The result is aneuploidy. Neurofibromatosis
is not due to chromosome failure during meiosis. Polyploidy occurs when a euploid cell
has more than the diploid number of chromosomes. Conjoined twins are not due to
chromosome failure during meiosis.
REF: p. 43
7. A cell that does not contain a multiple of 23 chromosomes is called a _____ cell.
a. diploid
b. euploid
c. polyploid
d. haploid
ANS: C
A polyploid cell is one in which a euploid cell has more than 23 pairs of chromosomes. A
diploid cell is when the somatic cell nucleus has 46 chromosomes in 23 pairs. A euploid
cell is a cell with multiples of the normal number of chromosomes. A haploid cell has only
one member of each chromosome pair, for a total of 23 chromosomes.
REF: p. 42
8. A 20-year-old pregnant female gives birth to a stillborn child. Autopsy reveals that the
fetus has 92 chromosomes. What term may be on the autopsy report to describe this
condition?
a. Biploidy
b. Triploidy
c. Tetraploidy
d. Aneuploidy
ANS: C
Tetraploidy is a condition in which euploid cells have 92 chromosomes. Biploidy is a
euploid cell with two times more chromosomes, or 46. Triploidy is a zygote that has three
copies of each chromosome, rather than the usual two. Aneuploidy is when an aneuploid
cell does not contain a multiple of 23 chromosomes.
REF: p. 42
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