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Molecular Basis of Disease—Pathology, Laboratory Medicine - Part 2 (18 test)
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1. A 28-year-old female presents for evaluation after failing to become pregnant after 3 years of Her husband’s sperm counts and her uterine sonogram plus clotting and hormone studies are all normal, and tubal insufflation has failed to influence fertility. Her physician then notes a positive urine reducing substance that turns out to be galactose, and orders testing of the GALT enzyme that converts UDP-galactose (substrate) to UDP-glucose (product) and is responsible for classical galactosemia (MIM*230400). The result shows a slightly low value for GALT activity with none of the common mutant alleles detected by DNA sequencing. The physician recalls the occurrence of ovarian dysfunction in galactosemia and invites collaboration with the pathologist to measure the Km of the female’s GALT enzyme to see if an alteration might justify detailed DNA sequencing studies. The amount of UDP-galactose to UDP-glucose conversion in 1 minute is measured using the same amount of enzyme (E) at 6 increasing UDP-galactose concentrations. Which of the following analyses would be most useful for determining the Km?
- Plot of E against S
- Plot of 1/Vi versus 1/S
- Plot of Vi versus S
- Plot of 1/E versus 1/S
- Plot of Vmax versus 1/S
2. A 3-day-old Caucasian girl has a cleft palate, heart defect, extra fifth fingers, scalp defect (absent skin exposing underlying flesh), and unusual face with narrow distance between the Her physician orders a routine karyotype that shows 46 chromosomes with extra material on one homolog of the chromosome 5 pair. This chromosomal abnormality is best described by which of the following terms?
- Balanced rearrangement
- Ring formation
- Unbalanced rearrangement
3. A 10-year-old African American boy is referred to the physician because of learning problems and some behavior His family history is unremarkable. Physical examination reveals tall stature with few anomalies except for single palmar creases of the hands and curved fifth fingers (clinodactyly). The physician decides to order a karyotype. Which of the following indications for obtaining a karyotype best explains the physician’s decision in this case?
- A couple with multiple miscarriages or a person who is at risk for an inherited chromosome rearrangement
- A child with ambiguous genitalia who needs genetic sex assignment
- A child with an appearance suggestive of Down syndrome or other chromosomal disorder
- A child with mental retardation and/or multiple congenital anomalies
- A child who is at risk for cancer
4. A 4-year-old Caucasian girl presents with short stature, web neck, and other features suggestive of Turner syndrome, but also has mild mental disability. Her chromosome studies reveal 90,XX/92,XXXX with about 10% abnormal cells in blood and 20% in These results can be described as which of the following?
- Triploidy mosaicism
- Tetraploidy without mosaicism
- Trisomy with mosaicism
5. Which of the following is the proper cytogenetic notation for a female with Down syndrome mosaicism?
- 47,XX,+21/46,XX e.
6. Children with type IV glycogen storage disease (MIM*232500) accumulate abnormal glycogen, causing them to have progressive liver damage in addition to the low blood glucose (hypoglycemia), increased triglycerides and cholesterol (hyperlipidemia), and high uric acid (hyperuricemic) due to deficient glycogenolysis (see High-Yield Facts, Table 3). Type IV glycogen storage is autosomal recessive. Autosomal recessive conditions are correctly characterized by which of the following statements?
- They are often associated with deficient enzyme activity.
- Both alleles contain the same mutation.
- They are more variable than autosomal dominant conditions.
- Most persons do not carry any abnormal recessive genes.
- Affected individuals are likely to have affected offspring.
7. A family with retinitis pigmentosa is encountered, and the pedigree shown below is What is the risk that a son born to individual III-3 would be affected?
- Virtually 0
8. Females occasionally have symptoms of X-linked recessive diseases such as Duchenne muscular dystrophy, hemophilia, or color Which of the following is the most common explanation?
- Nonrandom lyonization
- X-chromosome trisomy (47,XXX)
- X autosome–balanced translocation that disrupts the particular X-chromosome locus
- Turner syndrome (45,X)
- 46,XY karyotype in a female
9. A Caucasian couple presents for genetic counseling after their first child, a son, is born with short limb dwarfism and diagnosed with autosomal dominant achondroplasia (MIM*100800). The physician obtains the following family history: the husband is the firstborn of four male children, and his next oldest brother has cystic fibrosis (MIM*219700). The wife is an only child, but she had DNA screening because a second cousin had cystic fibrosis and she knows that she is a There are no other medical problems in the couple or their families. The physician should now draw the pedigree with the female member of any couple on the left. The generations are numbered with Roman numerals and individuals with Arabic numerals; individuals affected with achondroplasia or cystic fibrosis are indicated. Which of the following risk figures applies to the next child born to this husband and wife?
- Achondroplasia ½, cystic fibrosis ¼
- Achondroplasia ½, cystic fibrosis 1/8
- Achondroplasia virtually 0, cystic fibrosis ¼
- Achondroplasia virtually 0, cystic fibrosis 1/6
- Achondroplasia virtually 0, cystic fibrosis 1/8
10. Isolated cleft lip and palate (meaning no other congenital anomalies are present) is a multifactorial trait. The recurrence risk of isolated cleft lip and palate is which of the following?
- The same in all families
- Not dependent on the number of affected family members
- The same in all ethnic groups
- The same in males and females
- Affected by the severity of the cleft
11. Availability of DNA testing for many single disease traits has allowed routine prenatal screening of couples for disorders prevalent in their ethnic group. Which of the following genetic disorders has a similar incidence in different ethnic groups and would not be subject to different criteria for screening?
- Cystic fibrosis
- Tay-Sachs disease
- Down syndrome
- Sickle cell anemia
12. In family with Charcot-Marie-Tooth disease (CMT), restriction analysis using sites flanking the CMT gene on chromosome 17 yields one large abnormal fragment and one smaller fragment that is seen in What is the probable inheritance mechanism in this family?
- X-linked recessive
- Autosomal dominant
- Autosomal recessive
- X-linked dominant
13. Many family studies employing DNA have the potential to demonstrate If the physician ordering these analyses does not discuss this possibility with the couples involved, he or she is in violation of which of the following?
- Patient confidentiality
- Patient rights
- Informed consent
- Standards of care
- Malpractice guidelines
14. The genesis of Prader-Willi syndrome by inheritance of two normal chromosomes from a single parent is a consequence of which of the following?
- Germinal mosaicism due to paternal mutation
- Genomic imprinting due to uniparental disomy
- Chromosome deletion
- Chromosome rearrangement
15. A child is born with spina bifida, a defect in the lower spinal cord and meninges that may cause bladder and lower limb The family history reveals that the father had a small spina bifida that was repaired by surgery. Which of the following is the most critical aspect of the medical evaluation as it pertains to genetic counseling?
- A search for additional anomalies to determine if the child has a syndrome
- A karyotype on the child
- A serum folic acid level on the child
- A spinal x-ray on the mother
- A spinal x-ray on the father
16. A 1-year-old child develops fever and vomiting, and is unable to keep food down for 2 The physical examination discloses no congenital anomalies, and the baby resembles his parents. Which of the following laboratory findings are most likely if the child has a disorder of fatty acid oxidation?
- Hypoglycemia, acidosis, and elevated urine dicarboxylic acids
- Alkalosis and elevated serum ammonia
- Acidosis and elevated urine reducing substances
- Hypoglycemia, acidosis, and elevated serum leucine, isoleucine, and valine
- Hepatomegaly, elevated serum liver enzymes, and elevated tyrosine
17. Laboratory tests on a sick child reveal a low white blood cell count, metabolic acidosis, increased anion gap, and mild Measurement of plasma amino acids reveals elevated levels of glycine, and measurement of urinary organic acids reveals increased amounts of propionic acid and methyl citrate. Which of the following processes is most likely?
- Diabetes mellitus
- A fatty acid oxidation disorder
- Vitamin B12 deficiency
- Propionic acidemia
- A disorder in glycine catabolism
18. Neonatal screening is mandated in all states, but examines different numbers of diseases. Most commonly tested are phenylketonuria (PKU-MIM*261600), galactosemia (MIM*230400), congenital hypothyroidism, and sickle cell anemia (MIM*603903). Recently, a supplemental newborn screen using tandem mass spectrometry is being adopted by many states, allowing recognition of the more common organic acidemias and fatty acid oxidation Which of the following is the most important characteristic to qualify a disorder for newborn screening?
- A highly accurate diagnostic test
- A high frequency of disease
- An advantage for treatment from early diagnosis
- Use of microbial technology like the Guthrie method
- A minimal incidence of false positive tests