Question 1

The normal white blood cell count for an adult ranges from

Accepted Answer

The normal white blood cell count for an adult ranges from 5000 to 10,000/mm³ of blood. Option A is too low and options B and D are too high for the normal range.

Question 2

A biologic reaction is produced by 4 Gyt of a test radiation.It takes 16 Gyt of 250-kVp x-rays to produce the same biologic reaction.What is the relative biologic effectiveness (RBE)of the test radiation?

Accepted Answer

The relative biologic effectiveness (RBE) is calculated as the dose of the reference radiation (250-kVp x-rays) divided by the dose of the test radiation, both required to produce the same biologic effect. Thus, RBE = 16 Gyt / 4 Gyt = 4.

Question 3

One micron (mm)= __________.

Accepted Answer

One micron (mm) is equal to 10-⁶ m.

Question 4

Which of the following curves illustrates the radiation sensitivity of a particular type of cell?

Accepted Answer

The cell survival curve is used to study the radiation sensitivity of a particular type of cell by plotting the surviving fraction of cells against the radiation dose. It shows how many cells survive a given radiation dose and provides useful information about the radiation response of the cell population.

Question 5

Direct action may occur after exposure to any type of radiation,but it is much more likely to happen after exposure to

Accepted Answer

Direct action is the result of the ionization of molecules in living tissue by highly energetic particles such as alpha particles, which have high linear energy transfer (LET). Low-LET radiation such as x-rays and gamma rays have a lower chance of directly causing damage in this way, while nonionizing radiation such as microwaves cannot cause direct ionization.

Question 6

The radiation dose required to produce mitotic death is

Accepted Answer

Mitotic death is a type of cell death that occurs during mitosis, the process of cell division. Apoptosis is a type of cell death that occurs in non-dividing cells. The radiation dose required to produce mitotic death is less than the dose needed to produce apoptosis in slowly dividing cells or nondividing cells.

Question 7

Which of the following humans is most radiosensitive?

Accepted Answer

During the first trimester of pregnancy, the developing embryo and fetus are most radiosensitive. This is because the cells are rapidly dividing and differentiating, making them more vulnerable to the damaging effects of radiation. As the fetus develops, it becomes less sensitive to radiation, and by the third trimester, it is relatively resistant. Mature adults and children are also less radiosensitive than embryos in the first trimester.

Question 8

Based on current data,which of the following would be considered a safe radiation dose for the gonads of both males and females?

Accepted Answer

There is no safe radiation dose for the gonads, as even small doses can result in harm to fertility and genetic material. It is important to minimize radiation exposure whenever possible.

Question 9

When free radicals previously produced by the interaction of radiation with water molecules act on a molecule such as DNA,the damaging action of ionizing radiation is indirect in the sense that the radiation is not the immediate cause of injury to the macromolecule.What is the immediate cause of this damage?

Accepted Answer

When free radicals previously produced by the interaction of radiation with water molecules act on a molecule such as DNA, they directly cause damage to the macromolecule. The free radicals are highly reactive and can react with other nearby molecules, such as DNA, causing a chain reaction of further damage. This is the immediate cause of the damage, rather than the radiation itself.

Question 10

Which of the following groups of cells is most radiosensitive?

Accepted Answer

Lymphocytes are the most radiosensitive cells because they are actively dividing and have a short life span. The rapid turnover of lymphocytes makes them more susceptible to damage from ionizing radiation. Adult nerve cells, erythrocytes, and muscle cells are much less radiosensitive because they do not undergo active mitosis and have a longer lifespan.

Question 11

OH* + OH* = __________.

Accepted Answer

The reaction between two hydroxyl radicals (OH*) typically forms hydrogen peroxide (H₂O₂).

Question 12

Because the genetic information to be passed on to future generations is contained in the strict sequence of nitrogenous bases,the loss or change of a base in the DNA chain represents a (an)

Accepted Answer

The loss or change of a base in the DNA chain represents a mutation, which can have significant consequences on the structure and function of proteins encoded by the affected genes. Aneuploidy refers to the abnormal number of chromosomes, whereas a bleb is a bulge or protuberance in a cell membrane. A covalent cross-link represents a chemical bond between two molecules, which can affect their properties but is not directly related to DNA base changes.

Question 13

Which of the following groups of cells is least radiosensitive?

Accepted Answer

Adult nerve cells are in a non-proliferative state and are thus less sensitive to radiation compared to rapidly dividing cells such as lymphocytes, immature spermatogonia, and nerve cells in an embryo-fetus.

Question 14

Which of the following is/are considered low-LET radiation(s)?
1)X-rays
2)Alpha particles
3)Gamma rays

Accepted Answer

1 and 3 only. X-rays and gamma rays are considered low-LET (Linear Energy Transfer) radiations because they have a relatively low rate of energy transfer to the surrounding medium. Alpha particles, on the other hand, are high-LET radiation due to their high mass and charge, leading to a higher rate of energy transfer.

Question 15

Which of the following statements is true concerning patients who receive radiation exposure from a routine radiographic procedure such as a chest x-ray?

Accepted Answer

Routine radiographic procedures such as a chest x-ray typically involve low levels of radiation exposure that are not expected to cause appreciable damage to the blood or the blood-forming organs. The amount of radiation exposure received from these procedures is typically within the safe limits recommended by radiation safety guidelines.

Question 16

A periodic blood count is not recommended as a method for monitoring occupational radiation exposure because
1)biologic damage from ionizing radiation cannot be determined from a blood test.
2)biologic damage has already been sustained when an irregularity is seen in the blood count.
3)a traditional blood count is a relatively insensitive test that is unable to indicate exposures of less than 10 cGy.

Accepted Answer

2 and 3 are correct because biologic damage from ionizing radiation indeed may have already occurred by the time changes are observed in a blood count, and traditional blood counts are relatively insensitive, often unable to detect exposures below 10 cGy.

Question 17

Because the master molecule is unique in any given cell,no similar molecules in the cell are available to replace it;if a critical location on the master molecule is a target receiving multiple hits from ionizing radiation,the master molecule may be inactivated.If this occurs,what is the consequence for the affected cell?

Accepted Answer

If the master molecule is inactivated, normal cell function will cease and the cell will die. The master molecule is essential for proper functioning and survival of the cell, so its inactivation would have severe consequences. Choices A and B are not relevant to this scenario, and choice C is not accurate as disruption of the master molecule would have a significant impact on the entire cell rather than just the cell chemistry.

Question 18

Which of the following gonadal radiation doses may cause permanent sterility in a male human?

Accepted Answer

A dose of 5.0 or 6.0 Gyt can cause permanent sterility in a male human. This is because the testes are highly sensitive to radiation, and doses above 2.5 Gyt can result in significant damage to the germinal epithelium, leading to infertility. Lower doses may also cause temporary or partial sterility, but are more likely to result in a return to normal fertility over time.

Question 19

The term apoptosis is synonymous with

Accepted Answer

Apoptosis is a type of programmed cell death, which involves the controlled degradation of cellular components and ultimately the fragmentation and clearance of the cell by neighboring cells or phagocytes. Meiosis and mitosis are both types of cell division, while a point mutation refers to a specific type of genetic mutation. Therefore, option A is the correct answer.

Question 20

When LET increases,the chance of producing a significant biologic response in the radiosensitive DNA macromolecule

Accepted Answer

LET (linear energy transfer) is a measure of the amount of energy transferred per unit distance traveled by ionizing particles. When LET increases, the ionizing particles lose their energy rapidly over a shorter distance, leading to a higher probability of producing significant biologic damage, such as DNA damage. Therefore, the chance of producing a significant biologic response in the radiosensitive DNA macromolecule increases as LET increases.

Quiz 7: Molecular and Cellular Radiation Biology