Glossary

Band size - The size, measured in DNA base pairs, of the gene portion being looked at for mutations. Each portion of the gene studied has a different band size which distinguishes it from the others.

BRCA1 – A gene whose normal function in the body is unknown.   Certain inherited mutations in this gene may markedly increase a person's risk of breast cancer.

Case-control study - A study in which the risk factors of people with a disease are compared with the risk factors of those without a disease.  For example, in the Carolina Breast Cancer Study, women with breast cancer were compared to women without breast cancer to determine if they had different risk factors in their lives (for example, pesticide exposure) that may have increased their risk of getting breast cancer.

Control group – Subjects with whom comparison is made in a case-control or other epidemiologic study. Selection of appropriate controls is crucial to the validity of epidemiologic studies.

DNA sequencing - The process of determining the precise sequence of bases in a length of DNA.

Ductal carcinoma in situ (DCIS) - Ductal carcinoma in situ is the most common type of noninvasive breast cancer. There are cancer cells inside the ducts but they have not spread through the walls of the ducts into the fatty tissue of the breast nor spread to other organs in the body. More information on types of breast can be found at the American Cancer Society’s Breast Cancer Resource Center at http://www3.cancer.org/cancerinfo/load_cont.asp?ct=5&st=wi

Exon - The portion of the DNA sequence in a gene that contains the codons that specify the sequence of amino acids in a polypeptide chain, as well as the beginning and end of the coding sequence.

Flanking marker - The immediate or neighboring upstream or downstream sequence from a designated definitive structure such as a gene.

Generalizable – Whether the results of a study are applicable to other populations. Generalizability is a concern because an individual study is conducted on a particular sample of persons with certain characteristics. It is necessary to ask whether there are other groups of people to whom the results may or may not apply.

Germ line - A lineage of cells that contain the complete genome of the individual and produce the reproductive cells that transfer the genome to the next generation.

High-risk population – Persons who are at an increased risk of developing disease due to particular factors such as genetics or geographic location. Relating to breast cancer, high-risk families are those with 4 or more family members having had breast and/or ovarian cancer.

Invasive breast cancer - This type of breast cancer has broken through the wall of the duct and invaded the fatty tissue of the breast. At that point, it has the potential to metastasize, or spread, to other parts of the body through the lymphatic system (lymph nodes) and bloodstream. More information on types of breast can be found at the American Cancer Society’s Breast Cancer Resource Center at http://www3.cancer.org/cancerinfo/load_cont.asp?ct=5&st=wi

Matching – The process of making a study group and a comparison (control) group comparable with respect to certain factors that are not part of the main hypothesis. Matching is often done on such characteristics as age, sex, race, income group, etc. and is included into the study design to prevent the matched variables from affecting the estimate of risk and ultimately the conclusions of the study.

Mutation - the process by which a gene or some other DNA sequence undergoes a change in structure.  The change in structure may affect the function of the gene and may or may not lead to disease.

Pathology reports – Reports received from the laboratory which confirm or deny the state of disease of the subject under study.

PCR (polymerase chain reaction) product – The product that results from completing the laboratory genotyping tests which is used to determine whether mutations exist.

Polymorphism – The occurrence of two or more variations of a phenotype or gene.

Population-based – Pertaining to a general population defined by geographic or political boundaries.  When a study is population-based, it means it is conducted with people drawn from the general population, rather than certain groups like hospital patients or college students.

Prevalence – The number of instances of a given disease or other condition, such as a BRCA1 mutation, in a given population at a designated time.

Primer - A short single-stranded DNA fragment that is required to initiate polymerization of new DNA nucleotides. Used to determine the presence of particular mutations.

Randomization – Randomly assigning study subjects into groups to receive or not receive an experimental procedure or intervention. This type of subject assigning occurs only in randomized clinical trials.

Random sampling – Selecting sample subjects such that each possible subject has a fixed and determinate probability of selection.

Reliability – The degree to which the results obtained by a measurement procedure can be repeated by other studies.

Response rate – The number of completed interviews divided by the total number of persons who would have been interviewed if all had participated.   Researchers usually would like to have the highest response rate possible.

Sample (verb, to sample) - The process of selecting a number of subjects from all the subjects in a particular group.

Sampling scheme – The method or way a population is sampled.

Selection bias – Error due to systematic differences in characteristics between those who are selected for study and those who are not.

Tumor registry - A place where data, records, or laboratory tumor samples are kept and usually are made available for research or comparative study.

Validity (measurement validity) – The degree to which a measurement exactly measures what it is supposed to measure.

Variants – see Polymorphism.