Question

1. Microtubules make up mitotic spindles (True or False)2. P53 is an example of an oncogene (True or False)3. APC loss of function mutations typically causes a reduction of WNT signaling to promote polyp formation and colon cancer (True or False)4. Extravasation is the movement of a tumor from a primary tissue site into the blood circulation (True or False)5. A gain of function mutation in a gene typically causes a reduced function of the encoded protein (True or False)6. The RAS gene is an example of a tumor suppressor gene (True or False)7. Actin is polymerized and depolymerized in a process known as “dynamic instability” (True or False)8. P21 is an inhibitor of the G1 – S phase transition (True or False)9. Intermediate filaments include proteins in the vimentin family (True or False)10. RAB proteins are essential for vesicles to initiate docking to the target membrane (True or False)

Answer 1

1. Microtubules make up mitotic spindles: True

Explanation: Microtubules are made of alpha and beta-tubulin dimers. Microtubules are originated from the microtubule-organizing center that is centrosome. Microtubules form spindle fiber during cell division. The mitotic spindle segregates chromosomes into the daughter cells during mitosis.

2. P53 is an example of an oncogene:  False

Explanation: P53 is an example of a tumor suppressor gene that has a diverse role in the cell cycle control, DNA damage, etc. p53 is one of the most frequently mutated genes in human cancer and is mutated in the early stages of lung, skin, head, and neck, and esophageal cancers.

3. APC loss of function mutations typically causes a reduction of WNT signaling to promote polyp formation and colon cancer: False

Explanation: APC participates in a cytoplasmic complex that promotes the destruction of β-catenin. Loss of function mutations in APC triggers constitutive activation of the canonical WNT signaling pathway which is a characteristic found in almost all colorectal cancers.

4. Extravasation is the movement of a tumor from a primary tissue site into the blood circulation: False

Explanation: Extravasation is the leakage of blood, lymph, or other fluid, such as an anticancer drug, from a blood vessel or tube into the tissue around it. The movement of a tumor from a primary tissue site into the blood circulation is known as metastasis.

5. A gain of function mutation in a gene typically causes a reduced function of the encoded protein: False

Explanation: A gain of function mutation in a gene typically causes an amplification of the function of the encoded protein.

6. The RAS gene is an example of a tumor suppressor gene: False

Explanation: The RAS gene is an example of an oncogene. RAS gene encodes Ras proteins that are family members belong to a class of protein called small GTPase, and are involved in transmitting signals within cells. They act as switches that turn on or off the signaling pathways. Mutation in this gene can cause constitutive activation of the signaling pathway leading to uncontrolled proliferation of cells.

7. Actin is polymerized and depolymerized in a process known as “dynamic instability”: False

Explanation: Actin filaments show treadmilling while microtubules show dynamic instability. Dynamic instability is the rapid cycle of polymerization and the shrinking of microtubules. Trademilling is a process in which there is the simultaneous addition of actin monomers at the pulse end of actin filament and removal of actin monomers from its minus end.

8. P21 is an inhibitor of the G1 – S phase transition: True

Explanation: p21 is a potent cyclin-dependent kinase inhibitor (CKI) that inhibits the activity of cyclin-CDK2, -CDK1, and -CDK4/6 complexes, and thus functions as a regulator of cell cycle progression at G1 and S phase.

9. Intermediate filaments include proteins in the vimentin family: True

Explanation: Intermediate filaments are one of the three types of cytoskeletal elements. They are composed of a variety of proteins that are expressed in different types of cells. There are six types of intermediate filaments. Vimentin is a type III intermediate filament found in smooth muscle cells, fibroblasts, and WBCs. It forms a network that extends from the nucleus to periphery.

10. RAB proteins are essential for vesicles to initiate docking to the target membrane: True

Explanation: Rab GTPases regulate many steps of membrane trafficking, including vesicle formation, vesicle movement along with actin and tubulin networks, and membrane fusion.