Important things to remember

Question 1

What is ionisation and excitation

Answer 1

• Radiation can produce effects in the human body at an atomic level
• Interactions involve the excitation or ionisation of orbital electrons and result in energy being deposited in tissue which can cause changes to molecules

Question 2

What may ionisation cause

Answer 2

the chemical binding properties of the atom to change, it may also cause a break in the molecule or relocation of the atom if the atom is part of a large molecule

Question 3

What may happen as time progresses after ionisation

Answer 3

The abnormal molecule may not be able to function normally or at all, this may result in cell death

Question 4

Is the process reversible

Answer 4

Yes ionisation itself is a reversible process because an ionised atom can regain a free electron and return to its neutral state

Question 5

How is ionisation reversible when it is a cause of deterministic effects, yet deterministic effects are not reversible

Answer 5

Only the ionisation is reversible, the biological damage caused by it (deterministic effects) is not.

Question 6

List the main 5 structures of an animal cell

Answer 6

Nucleus: Contains genetic material (DNA) and controls cell activities.

Cell membrane: A protective barrier that regulates what enters and exits the cell.

Cytoplasm: A jelly-like substance where cell processes occur.

Mitochondria: The powerhouse of the cell, producing energy (ATP) through respiration.

Endoplasmic reticulum (ER): Transports proteins and other materials; the rough ER has ribosomes, and the smooth ER is involved in lipid synthesis.

Question 7

What are the 4 phases of the cell cycle

Answer 7

Mitosis - most consistent time
(cytokinesis)
G1 - First gap in activity, most variable in length
The “s” phase - DNA synthesis phase
G2 - second gap in activity, if the cells stop progressing they go into G0 which is the cell cycle arrest

Question 8

What happens in the Mitosis phase

Answer 8

During mitosis, a single cell divides to produce two genetically identical daughter cells. The process is divided into several phases

Question 9

What happens in the G1 phase

Answer 9

Cellular contents except chromosomes are duplicated

Question 10

What happens in the S phase

Answer 10

Each of the 46 chromosomes are duplicated by the cell

Question 11

What happens in the G2 phase

Answer 11

The cell double-checks its duplications for any errors, making any necessary repairs.

Question 12

When is radioresistance greatest in the cell cycle

Answer 12

At the end of the S phase due to the repairs that are more likely to take place after the DNA has replicated, it can also be at the beginning of G1, if G1 is long, and be more sensitive at the end of G1

Question 13

What cells are more likely to be malignant, fast-growing or normal

Answer 13

Fast growing cells are more likely to be malignant, these are cells which have a total cell cycle time of 10 hours

Question 14

What is the cell cycle time of stem cells, what are stem cells

Answer 14

10 days it the total cycle, in normal tissue such as skin. Stem cells are pure cells, with no infected DNA or chromosome which can produce a consistent production of similar cells.

Question 15

What is cell cycle progression

Answer 15

This is where the cells are checked by multiple molecular checkpoint genes.

Question 16

What is the function of the molecular checkpoint genes

Answer 16

To ensure the correct order of cell cycle events, the genes involved in radiation effects halt the cells in G2 so an inventory can be taken of chromosome damage, and the repair will be initiated and completed before mitosis is attempted.

Question 17

What happens to cells that lack checkpoint genes

Answer 17

They are sensitive to radiation-induced cell killing, and carcinogenesis

Question 18

What is DNA and RNA

Answer 18

Deoxyribonucleic Acid: DNA is the molecule that carries genetic instructions for the development, functioning, growth, and reproduction of all living organisms. It is double-stranded and structured as a double helix that is held together by hydrogen bonds. DNA holds the code for proteins that determine an organism’s traits.

Ribonucleic Acid: RNA is a single-stranded molecule that plays several roles in gene expression. Its main function is to convert the genetic information in DNA into proteins through transcription and translation. RNA also plays a role in other cellular processes.

Question 19

DNA complimentary pairs

Answer 19

adenine with thymine
cytosine with guanine
- each half constitutes a template for reconstruction of the other half.

Question 20

Are single strand or double-strand breaks more important in regards with radiation

Answer 20

Single strand breaks are of little biological consequence because they are repaired readily using the opposite strand as a template.

Double strand breaks are more important lesions produced in chromosomes by radiation. Two double-strand breaks may result in cell killing, carcinogenesis, or mutations.

Question 21

What are chromosome aberrations

Answer 21

The cell trying to repair lethal cell damage, which can lead to chromosome aberrations (abnormalities)

Question 22

What are the chromosome aberrations it can lead to

Answer 22

Depending on the types of aberrations they can be lethal or nonlethal but result in mutations that can be perpetuated in subsequent cell divisions.

Question 23

What are the 3 types of radiation-induced chromosome aberrations

Answer 23

• Inversion
• symmetric translocation
• Deletion

Question 24

What is inversion

Answer 24

Inversion: A segment of a chromosome is reversed end to end within the same chromosome. No genetic material is lost, but the sequence of genes in that segment is altered.

Question 25

What is translocation

Answer 25

Translocation: A segment of one chromosome breaks off and attaches to a different chromosome. This can result in changes in gene expression and can disrupt the normal function of genes.

Question 26

What is deletion

Answer 26

Deletion: A chromosome aberration where a segment of the chromosome is lost. This loss of genetic material can result from two breaks in the chromosome and improper repair, potentially leading to genetic disorders due to missing essential genes.

Question 27

What is the difference between DNA and chromosomes

Answer 27

DNA molecules carry genetic information, whilst chromosomes are an organised structure of DNA and DNA-Bound proteins. (To protect and controls DNA’s function)

Question 28

What happens if chromosome aberrations occur in germ cells

Answer 28

The can be passed on as a genetic abnormality in the offspring

Question 29

What happens if chromosome aberrations occur in somatic cells

Answer 29

They can lead to carcinogenesis, the development of cancers.

Question 30

What are oncogenes

Answer 30

Genes that affect cancer incidence

Question 31

How do they affect cancer risk through deletion

Answer 31

if an oncogene is lost due to deletion, the person is at higher risk for cancer formation. Poorly differentiated cancer cells lead to deadly cancer