1.Genetic disorders that involve a single-gene trait are characterized by:
A) Multifactorial gene mutations
B) Chromosome rearrangements
C) Mendelian
... [Show More] patterns of transmission
D) Abnormal numbers of chromosomes
Ans: C
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Single-gene disorders are characterized by patterns of transmission that follow the
Mendelian patterns of inheritance. Multifactorial inheritance involves more than one gene
mutation, rearrangement of groups of genes, and uneven numbers of some chromosomes
in each cell.
2.In one family, a son was born with polydactyly toes while his sister had polydactyly
fingers. In explaining this phenomenon in genetic terms to the parents, which concept
should be addressed?
A) Aneuploidy of genes in all cells
B) Deficiencies in enzyme synthesis
C) Heterozygote dominant trait
D) Variable expressivity of a gene
Ans: D
Feedback:
Autosomal dominant disorders are characterized by variable gene penetrance (degree to
which the trait is displayed) and expression (differences in how the trait is displayed).
Aneuploidy is not a single-gene disorder and does not follow the Mendelian pattern of
inheritance. Deficiencies of enzyme synthesis are common in autosomal recessive
disorders. X-linked inheritance can be dominant or recessive, but it is not autosomal.
3.A woman who is a carrier for which of the following diseases possesses the greatest
likelihood of passing the disease to her future children when heterozygous pairing exists?
A) Phenylketonuria (PKU)
B) Tay-Sachs disease
C) Neurofibromatosis
D) Cystic fibrosis
Ans: C
Feedback:
Neurofibromatosis is an autosomal dominant genetic disorder with a consequent 50%
chance of passing the disease to offspring. Tay-Sachs disease, PKU, and cystic fibrosis
are autosomal recessive disorders and are manifested only when both members of the
gene pair are affected.
4.A 16-year-old male presents to the clinic complaining of headaches, trouble hearing the
teacher in the front of the classroom, and ringing in the ears. He also revealed that every
time he goes swimming underwater, he gets disorientated (which never happened when [Show Less]