Radiobiology Chapter 31 Flashcards

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Questions and Answers

What is cytogenetic damage?

Radiation-induced structural change in chromosomes.

What is a point mutation?

Radiation damage that consists of a molecular lesion of the DNA and causes genetic mutation.

What does target theory state?

The radiobiologic theory that says for a cell to die, after radiation exposure, its target molecule must be inactivated.

What does viscosity determine in a solution?

The degree of main chain scissions. Signup and view all the answers

What is crosslinking?

Some macromolecules have side structures that behave as though they have a sticky substance on their ends, and they attach to another macromolecule or to another segment of the same molecule. Signup and view all the answers

What is a radiation hit?

Occurs when a radiation interaction occurs with the target. Signup and view all the answers

What is a stochastic effect?

Describes the probability or frequency of the biologic response to radiation as a function of radiation dose. Disease incidence increases proportionally with dose, and there is no dose threshold. Signup and view all the answers

List the effects of irradiation of macromolecules in solution in vitro.

Main chain scission, cross-linking, point mutations, change in viscosity. Signup and view all the answers

How is solution viscosity used to determine macromolecular damage?

Viscosity of the solution increases after a high dose of radiation of macromolecules. It is a measure of the degree of main-chain scission of macromolecules. Signup and view all the answers

What is the difference between catabolism and anabolism?

Catabolism is the division of large molecules into smaller molecules. Anabolism is the construction of large molecules from smaller molecules. Signup and view all the answers

In what phase of the cell cycle does the DNA ladder in the middle of each rung consist of only a single chain?

Synthesis (S) phase Signup and view all the answers

Name the three principal observable effects of DNA irradiation.

Cell death, malignant disease, and genetic damage. Signup and view all the answers

Differentiate among transcription, transfer, and translation.

The genetic code of DNA is transcribed by messenger RNA (mRNA). It is then transferred to transfer RNA (tRNA), which translates it into a protein. Signup and view all the answers

Write the formula for radiolysis of water in which the atom of water is ionized.

H2O + energy in the form of radiation HOH+ + e−. Signup and view all the answers

What happens to radiation-induced free radicals within the cell?

They migrate within the cell, transferring energy to target molecules, and ultimately join with another molecule to be neutralized. Signup and view all the answers

Describe the molecular cause of a deterministic effect.

Each cell contains target sites on a target molecule, which must be hit in order to cause cell death. That is a deterministic effect. Signup and view all the answers

What happens to the quantity of DNA as the cell progresses from G1 to G2?

Parent DNA is replicated into two duplicate daughter molecules. The number of DNA molecules doubles. Signup and view all the answers

Chromosome aberrations are an example of what type of cell damage?

Cytogenetic damage. Signup and view all the answers

What happens when a single nucleotide base is lost?

The triplet code is destroyed. This is called a point mutation. Signup and view all the answers

What is the result of the equation H2O + Radiation?

HOH+ + e−. Signup and view all the answers

What does HOH+ dissociate into?

H+ + OH*. Signup and view all the answers

What does HOH− dissociate into?

OH− + H*. Signup and view all the answers

What molecular change results in a stochastic effect?

Damage to the DNA that results in abnormal metabolic activity is the principal cause of stochastic effects. Signup and view all the answers

Describe the characteristics of a free radical.

Free radicals are highly reactive and unstable. They carry excess energy that can be transferred to other molecules to disrupt bonds and produce point lesions at some distance from the original ionizing event. Signup and view all the answers

What is the difference between direct effect and indirect effect?

A direct effect exists when the ionizing radiation interacts directly with the target molecule DNA. An indirect effect occurs when the interaction is with some other molecule, resulting in the formation of free radicals, which then transfer this excess energy to the DNA. Signup and view all the answers

How much DNA is in a cell?

The DNA molecule is not found in abundance in the cell. Signup and view all the answers

Study Notes

Cytogenetic Damage and DNA Mutations

Cytogenetic damage refers to radiation-induced structural changes in chromosomes.
Point mutation involves a molecular lesion in DNA that leads to genetic mutation.

Radiation Interaction and Effects

Target theory states that for a cell to die post-radiation exposure, its target molecule must be inactivated.
Stochastic effects relate to the probability of biological responses to radiation increasing with dose, with no specific dose threshold.

Macromolecular Changes Due to Irradiation

Effects of irradiation on macromolecules include main chain scission, cross-linking, point mutations, and changes in viscosity.
Viscosity increases after high radiation doses, helping assess the degree of damage in macromolecules.

Catabolism vs. Anabolism

Catabolism involves breaking down large molecules into smaller ones, while anabolism constructs large molecules from smaller units.

Cell Cycle and DNA Characteristics

In the synthesis (S) phase of the cell cycle, the DNA ladder consists of open links on a single chain.
As cells progress from G1 to G2, parent DNA replicates into two duplicate daughter molecules, effectively doubling the DNA content.

Principles of Molecular Genetics

DNA's genetic code is transcribed by mRNA, transferred to tRNA, and translated into proteins during gene expression.

Radiolysis of Water

Radiolysis of water involves the ionization of water molecules, producing HOH+ and an electron: H2O + energy = HOH+ + e−.

Free Radicals and Cell Damage

Radiation-induced free radicals migrate within cells, transferring energy to target molecules and subsequently neutralizing by joining with other molecules.
Free radicals are unstable, highly reactive entities that can disrupt bonds, causing point lesions distantly from the original ionizing event.

Deterministic Effects and Cell Damage

Deterministic effects result from specific target sites on molecules being hit, causing cell death.
Cytogenetic damage includes chromosome aberrations indicative of structural changes from radiation exposure.

Molecular Changes and DNA Quantity

Loss of a single nucleotide base destroys the triplet code, resulting in a point mutation.
Radiation can dissociate water molecules into ions: HOH+ yields H+ and OH*, while HOH− yields OH− and H*.

Understanding Direct vs. Indirect Effects

Direct effects of radiation involve interactions with DNA, while indirect effects occur through interactions with other molecules that form free radicals affecting DNA.

Overview of DNA in Cells

DNA is present in limited quantities within the cell, highlighting its critical role in genetic information storage and transfer.

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Description

Explore key concepts in radiobiology with these flashcards from Chapter 31 of Bushong. Learn about cytogenetic damage, point mutations, and target theory in relation to radiation exposure. Perfect for students seeking to reinforce their understanding of radiation effects on cellular structures.