Question 1

Which of the following best describes the structural and functional differences between epithelial tissue and connective tissue in animals?

Accepted Answer

Epithelial tissue forms tightly packed sheets that act as barriers and regulate transport, while connective tissue is composed of cells embedded in an extracellular matrix (ECM) that provides structural support.

Question 2

Cadherins are critical for cell-cell adhesion in epithelial tissues. Which of the following statements about cadherins is TRUE?

Accepted Answer

Cadherins interact with catenins inside the cell to link to the actin cytoskeleton, and loss of function mutations can promote cancer cell invasion.

Question 3

Which molecule mediates transient cell-cell adhesion during immune cell migration?

Accepted Answer

Selectins

Question 4

Tight junctions and gap junctions are specialized cell-cell contacts. Which statement correctly distinguishes their functions?

Accepted Answer

Tight junctions form a seal to prevent paracellular transport, mediated by claudins, while gap junctions allow direct communication between cells via connexins.

Question 5

Which of the following is NOT a class of extracellular matrix (ECM) molecules in animal cells?

Accepted Answer

Actin filaments

Question 6

Vitamin C is essential for collagen assembly because it acts as a cofactor for which biochemical process?

Accepted Answer

Hydroxylation of proline and lysine residues in collagen, which stabilizes the triple helix structure.

Question 7

A patient with osteogenesis imperfecta is most likely to have a mutation affecting which component?

Accepted Answer

Collagen

Question 8

Which protein is defective in Junctional Epidermolysis Bullosa, leading to skin blistering?

Accepted Answer

Laminin

Question 9

Which of the following best describes the role of dystrophin in muscle cells?

Accepted Answer

Dystrophin anchors actin filaments to the ECM via the dystrophin-associated protein complex (DAPC), maintaining muscle integrity.

Question 10

Stem cell potency refers to a cell's ability to differentiate into various cell types. Which of the following correctly matches the type of potency with its definition?

Accepted Answer

Pluripotent: Can differentiate into all cell types except extraembryonic tissues.

Question 11

Which technique is used to produce both reproductive and therapeutic clones, and why is its success rate low?

Accepted Answer

Somatic cell nuclear transfer (SCNT); low success rate due to incomplete reprogramming of the donor nucleus.

Question 12

Which of the following statements about induced pluripotent stem (iPS) cells is TRUE?

Accepted Answer

iPS cells are produced by introducing specific transcription factors into somatic cells, reprogramming them to a pluripotent state.

Question 13

Which of the following is a hallmark of cancer cells?

Accepted Answer

Uncontrolled proliferation and evasion of apoptosis

Question 14

Proto-oncogenes can become oncogenes through several mechanisms. Which of the following is NOT a mechanism for this conversion?

Accepted Answer

Loss of heterozygosity

Question 15

The two-hit hypothesis explains the development of hereditary and sporadic cancers. Which statement best describes this hypothesis?

Accepted Answer

Both alleles of a tumor suppressor gene must be inactivated for cancer to develop.

Question 16

Which cell cycle checkpoint ensures that DNA is undamaged before the cell enters mitosis?

Accepted Answer

G2 checkpoint

Question 17

The Ras and PI3K-Akt pathways are important in cell proliferation and survival. Which of the following correctly describes their roles?

Accepted Answer

Ras activates PI3K, which in turn activates Akt, promoting cell survival and proliferation.

Question 18

Loss of function mutations in p53 can lead to which of the following outcomes?

Accepted Answer

Reduced DNA repair and increased risk of cancer

Question 19

Which of the following best describes the major steps of apoptosis?

Accepted Answer

Cell shrinkage, chromatin condensation, membrane blebbing, and formation of apoptotic bodies

Question 20

Chronic Myelogenous Leukemia (CML) is caused by a specific chromosomal translocation. Which drug targets the resulting fusion protein, and why might resistance develop?

Accepted Answer

Imatinib (Gleevec) targets the BCR-ABL fusion protein; resistance may develop due to additional mutations in the BCR-ABL gene.

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