Please also see the following pages for more detailed information.
Allele
The two individual variations of a specific gene – one on each chromosome, one chromosome inherited from each parent.
Amplification
Duplication of genetic material.
Antecedent Relatives
Relatives descendent from a person born before the individual concerned.
Assay
A procedure which measures the property or concentration of a specific substance or chemical constituent.
At-Risk Relatives
Relatives who have a presumed or molecularly identified risk for developing a particular disease.
Bilateral Retinoblastoma
Retinoblastoma affecting both eyes.
Chromosome
A bundle of coiled DNA which is visible under a microscope. Normally each person has 22 pairs of chromosomes and two unpaired sex chromosomes.
Chromosome 13 Deletion
The loss of DNA on chromosome 13, where the RB1 gene is located. This may involve all or part of the chromosome, as well as parts of adjacent chromosomes.
Clinical
Direct examination and/or treatment of a patient.
Constitutional Pathogenic Variant
A change in DNA sequence of a gene that can be passed to the next generation. This gene change may have been inherited from a parent, or occurred at conception or early in foetal development.
Conventional Screening
Repeated eye examination, including under anaesthetic, of young children perceived to be at risk for retinoblastoma.
Cytogenetic Analysis
Study of the microscopic appearance of chromosomes.
Descendants
Children, grandchildren etc. descended from a specific person.
Disease Morbidity
The prevalence, incidence, degree or severity of a disease,
DNA (Deoxyribonucleic Acid)
The molecule that encodes genetic information.
EUA (Examination Under Anaesthetic)
The clinical procedure used to identify and monitor tumours in the eyes of a person with, or at risk for, retinoblastoma.
Exon
The protein-coding DNA sequence of a gene.
Extended Family
Grandparents, aunts, uncles, cousins, in addition first degree relatives.
Familial Retinoblastoma
Retinoblastoma affecting more than one member of the same family, caused by the same RB1 pathogenic variant.
First Degree Relatives
Parents, siblings and offspring.
FISH (Fluorescent In-situ Hybridization)
A physical mapping approach that uses fluorescein tags to detect chromosomal changes.
Gene
An ordered sequence of DNA, located in a particular position on a particular chromosome, which encodes a specific protein.
Genetic Counselling
An educational process for individuals and families affected by or at risk for heritable disease. Provides information on the lifelong implications of a pathogenic variant, risk for other family members, screening protocols and reproductive options. Can organise genetic testing.
Genetic Testing
The process of analyzing the gene or genes of an individual to confirm, eliminate or reduce the risk that a heritable pathogenic variant is present.
Germline
The set of genetic information that is passed from one generation to the next.
Hereditary
A pathogenic variant that has been passed from parent to child.
Heritable
A pathogenic variant that can be passed on to the next generation, but is not necessarily inherited from a parent.
Immediate Family
Parents, siblings and offspring.
Informed Consent
An individual willingly agrees to participate in a specific activity, or allows his/her child to be involved in that activity, after first being advised of the need, process, benefits and risks.
Intron
A DNA sequence that interrupts the protein-coding sequence of a gene.
Karyotype
A microscope enabled photograph of an individual’s chromosomes records the number, size, and shape of each chromosome type to physically map major chromosomal alterations.
Molecular Genetics
The study of molecules important in biological inheritance.
Mosaicism
A heritable pathogenic variant that is present in only a fraction of cells throughout the body, due to its initiation after conception.
MYCN Gene
An oncogene that causes cancer when too many copies are made in a single cell.
MYCN Amplification
Duplication of the MYCN gene. Too many copies of MYCN in a retinal cell may cause retinoblastoma.
Non-Familial Retinoblastoma
Retinoblastoma that is not known to affect more than one member of the family.
Null RB1 Pathogenic Variant
An RB1 gene that fails to produce detectable RB protein.
Pathogenic Variant
A change in DNA sequence that damages gene function, increasing the individual’s susceptibility or predisposition to a certain disease or disorder.
PCR (Polymerase Chain Reaction)
A method used to amplify (make millions of copies of) a specific fragment of DNA.
Pedigree
A family tree diagram that shows how a specific disease has been inherited, and identifies family members at risk for inheritance of the predisposing pathogenic variant.
Penetrance
The probability that a heritable pathogenic variant will be expressed (cause a disease to develop).
Predisposed
Susceptibility to a disease due to inheritance of a genetic mutation, which may or may not result in actual development of the disease.
Pre-implantation Genetic Diagnosis
Genetic testing carried out during In Vitro Fertilization (IVF), when one parent has a known heritable RB1 pathogenic variant, to avoid passing that gene change to the child.
Prenatal Retinoblastoma Diagnosis
Identification of retinoblastoma before birth.
Prevalence
The proportion of people with a particular disease or pathogenic variant.
Proband
The first known affected person in a family
Promoter
DNA that controls expression of the gene.
Quantitative Multiplex PCR
A method which performs multiple sets of PCR reactions on several pieces of DNA simultaneously.
RB1 Gene
A tumour suppressor gene that causes cancer when both copies are altered in a single cell.
RB1 Pathogenic Variant / Gene Mutation / Mutant Allele
A change in DNA sequence that damages RB1 gene function and may cause retinoblastoma.
RB1+/-
One copy of the RB1 gene is altered while the other is normal.
RB1-/-
Both copies of the RB1 gene are altered.
RB1+/+MYCNA
Both copies of the RB1 gene are normal, and there are too many copies of the MYCN gene (A = amplification).
RB Protein
A large molecule coded for by the RB1 gene that is important in the control of cell division and specialization in general, and specifically blocks the development of retinoblastoma in retinal cells.
Reciprocal Translocation
A pair of chromosomes exchange DNA, resulting in shuffling of the genes and sometimes damage to genes.
Reduced Penetrance RB1 Pathogenic Variant
RB protein is identified at low levels and the RB1 gene may be partially functioning.
Retinoblastoma
Cancer of the retina, usually occurring in young children, caused by mutation of both RB1 alleles in a cell of the retina, or by amplification of the MYCN gene.
Retinoma
The benign precursor to malignant retinoblastoma.
RNA (Ribonucleic Acid)
An important chemical required for protein synthesis.
RT-PCR (Reverse Transcriptase-PCR)
A sensitive technique used to detect and measure the quantity of mRNA, which is responsible for gene expression and translates into protein.
Second Primary Cancers
Cancers in addition to retinoblastoma that are associated with a constitutional RB1 pathogenic vairant.
Sensitivity
An individual laboratory’s measured ability to identify pathogenic variants for a specific genetic disease.
Sequencing
The process used to determine the order of nucleotides (base sequences) in a DNA molecule, which in turn determines the structure of proteins encoded by that molecule.
Somatic Pathogenic Variant
A genetic change that has occurred in any cell other than the germ cells (egg or sperm) and is therefore neither inherited nor passed on to children.
Specificity
The probability that a laboratory does not find a pathogenic variant when there is none to be found.
Sporadic Pathogenic Variant
A genetic change that has occurred at or after conception and is therefore not inherited from a parent. This can refer to either a somatic or constitutional pathogenic variant.
Surveillance
Clinical assessment of children at risk for retinoblastoma, usually by Examination Under Anaesthetic.
Unaffected Carrier
An individual who carries a heritable pathogenic variant, but has not developed the associated disease.
Unilateral Retinoblastoma
Retinoblastoma affecting one eye (either left or right).
