USMDO practice test

Which of the following macro molecules is not a polymer?

Phospholipid

Where are the large and small subunits of ribosomes assembled?

Nucleolus

What is the motor protein that is associated with microtubules in the flagella?

Dynein

What is the motor protein that is associated with microtubules in the flagella?

Dynein

The uptake of which substance into cells requires receptor-mediated endocytosis?

LDL

How many NADH molecules are produced per acetyl-CoA in the citric acid cycle?

3

What does not function as a second messenger?

sodium ion (Na+)

Which of the following is not a difference between mitosis and meiosis?

separation of chromatids

Explanation: Sister chromatids separate in both mitosis (anaphase) and meiosis II (anaphase II). Synapsis, tetrad formation, crossing over, and chiasmata are unique to Meiosis I.

Which enzyme untwists the double-stranded DNA and separates the two strands?

Helicase

What is the gel electrophoresis of mRNA followed by labeled-probe hybridization called?

Northern blotting

Explanation: Southern = DNA, Northern = RNA, Western = Protein (Mnemonic: SNoW DRaP

What is one method of gene duplication in sexual organisms?

unequal crossing-over

Explanation: Misalignment of homologous chromosomes during meiotic prophase I leads to unequal exchange of genetic material, creating a duplication on one chromosome and a deletion on the other.

Which of the following is not a connective tissue?

Glia (neuroglia) are specialized support cells of nervous tissue, not connective tissue.

Which water-soluble vitamin is needed by pregnant woman to prevent birth defects?

Folic acid (Vitamin B_9) is crucial for neural tube development; deficiency leads to defects like spina bifida.

Which cell secretes pepsinogen in the stomach?

chief cell

Explanation: Chief cells secrete pepsinogen (inactive zymogen). Parietal cells secrete \text{HCl} and intrinsic factor.

Which organ or tissue synthesizes erythropoietin, the hormone that stimulates red blood cell production?

kidney

Explanation: Specialized interstitial cells in the renal cortex produce erythropoietin (EPO) in response to hypoxia.

Which is by far the major mechanism of carbon dioxide transport in the blood?

converted to bicarbonate ion and hydrogen ion

Explanation: Roughly 70% of \text{CO}_2 is transported in plasma as bicarbonate (\text{HCO}_3^-) via carbonic anhydrase in RBCs.

Which of the following is not a phagocyte?

mast cell

Explanation: Mast cells primarily degranulate and release histamine/inflammatory mediators during allergic responses rather than acting as professional phagocytes.

Which of the following hormone or compound has the least effect on blood pressure?

cortisol

Explanation: Epinephrine, angiotensin II, renin, and aldosterone all directly drive acute or long-term systemic blood pressure control. Cortisol plays a major role in metabolism/stress response and has far less acute direct effect on BP compared to the others.

In which structure are sperm stored after their maturation in the testes?

epididymis

Explanation: Sperm mature and are stored in the coiled tubule of the epididymis until ejaculation.

Which of the following structures is or are formed from ectoderm?

teeth

Explanation: Enamel (the outer layer of teeth) originates from ectoderm. Bone/skeleton and dermis stem from mesoderm, while digestive/respiratory linings stem from endoderm.

What is the neurotransmitter secreted by the motor neurons at the neuromuscular junction?

acetylcholine

Explanation: Somatic motor neurons release acetylcholine (ACh) at the neuromuscular junction to excite skeletal muscle fibers.

Which of the following bacterial diseases does not involve a G protein?

Tetanus

Which of the following is not the result of aneuploidy?

William syndrome

Explanation: Williams syndrome is caused by a microdeletion on chromosome 7, not aneuploidy (an abnormal whole-chromosome count like Trisomy 21, 13, 18, or 45,X / 47,XXY).

Which of the following is a proto-oncogene?

ras

Explanation: ras is a classic proto-oncogene (gain-of-function mutation causes hyperactive cell division). p53, p21, BRCA1, and APC are all tumor suppressor genes.

Which hormone is involved in diabetes insipidus?

vasopressin

Explanation: Diabetes insipidus is caused by a deficiency in or resistance to anti-diuretic hormone (ADH / vasopressin), leading to excessive excretion of dilute urine.

Which compound causes the symptoms of both inflammation and allergy?

histamine

Explanation: Histamine released by mast cells and basophils triggers vasodilation, increased vascular permeability, and classic allergic/inflammatory symptoms.