Midterms Radbio

Physical Phase

The ___ consists of interactions between the charged particles and the atoms with which the tissue is composed.

CHEMICAL PHASE

lonisation and excitation lead to the breakage of chemical bonds and formation of free radicals which are highly reactive.

BIOLOGICAL PHASE

In this phase the DNA aberrations and lesions are either repaired or mutations may occur and cell death.

Deterministic effect 

na determine mo yung effect sa certain degree of ionazing radiation

Stochastic effects

We are blinded. There is no threshold. Hindi na dedetermine yung effect.

Direct action of radiation

If radiation interacts with the atoms of the DNA molecule, or some other cellular component critical to the survival of the cell it is referred to as a direct effect.

INDIRECT ACTION OF RADIATION

If a cell is exposed to radiation, there is a higher probability of radiation interacting with the water that makes up most of the cell's volume.

RADIOLYSIS OF WATER

First step in radiolysis of water is the absorption of radiant energy that can cause ionisation or excitation.

IONISATION OF WATER MOLECULE

• This reaction needs 13 eV of energy.

• Radical ions formed are short lived.

• Form uncharged free radical.

EXCITATION OF WATER MOLECULE

The excited water molecules are not stable and soon undergo radiolysis giving rise to Ho and OHo radicals.

These aqueous electrons are strongly reducing agents and can cause dissociation of water molecules forming free radicals.

Single-Strand Break

A single lonisation cause the break in one of the strands of DNA molecules. The break can occur either at the bond between sugar and phosphate or between sugar and the base.

Double-Strand Break

If the breaks in the two strands are opposite to one another or separated by only a few base pairs DSB may occur.

DNA DAMAGE

 ___ is damaged by radiation provided in the kinds of doses normally used in radiotherapy.

Cells may die by different mechanisms

Mitotic death

Apoptosis

Mitotic death

Death while attempting to divide, that is, ___ death, is the dominant mechanism following irradiation.

Apoptosis

For some cells, programmed cell death is important. Whatever the mechanism, the outcome is the same.

They are of two types of chromosomal aberration

1. Structural aberrations

2. Numerical aberrations 

Structural aberrations

These occur due to a loss of genetic material, or a rearrangement in the location of the genetic material.

Numerical aberrations 

The number of chromosomes shows a change from normal diploid state.

Deletion

loss of chromosomal segment

duplication

repeat a segment

inversion

reverse segment

translocation

move segment

Trisomy

small gains

monosomy

small scale losses

Microarray analysi

 test to determine if you have future aberrations or instability 

Down Syndrome

A genetic disorder that causes delays in physical and intellectual development.

another term for Down syndrome

Neurodevelopmental syndrome

who first described the physical and behavioral characteristics 

 John Langdon Haydon 

 John Langdon Haydon Down who first described the physical and behavioral characteristics in 1862.

 John Langdon Haydon Down who first described the physical and behavioral characteristics in 1—2.

Turner Syndrome

Affects only females

Klinefelter syndrome 

Genetic condition where there's an extra X chromosome present in a male's genetic code

genetic code of Klinefelter syndrome 

47-XXY

Cri du chat syndrome 

is a rare genetic disorder caused by a missing section on a particular chromosome known as cat cry syndrome

another term for cri du chat syndrome

cat cry syndrome

Physical manifestation of cri du chat or cat cry syndrome

• droopy eyes/ wide spaced eyes (hypertelorism) 

• Extra nape skin

Wolf-Hirschhorn syndrome

is a well-known congenital malformation syndrome caused by deletion of the short arm of chromosome 4 (4p-).

Physical manifestations of Wolf-Hirschhorn syndrome

protruding forehead 

Prader-Willi syndrome (PWS) 

is a disorder caused by a deletion or disruption of genes in the proximal arm of chromosome 15.

Physical manifestation of Prader-Willi syndrome (PWS)

• high cholesterol

• Diabetes

• Life span 30 years old

• Physical manifestations: obese