Cell World Storyboard

DNA Drawing: BRCA1

Characters: Chromosome 17
Segment Directors: Warren
Start Date: April 23, 2000

Click On Image For Larger View


• The BRCA1 Breast Cancer Gene

This drawing arranges all exons, introns, repeats and other sequences in left to right order. Note the regions of approximate vertical homology. Now pass your mouse over the drawing and note how the exons that code for protein only constitute a small portion of the gene.

In 1990, through genetic linkage studies, a gene(BRCA1) was localized on chromosome 17 at band q21 that predisposes to a significant proportion of early-onset breast cancer. Later studies found BRCA1 increased susceptibility for ovarian cancer as well as breast cancer. A study of 214 families linked to 17q21 the cumulative risk for breast cancer associated with BRAC1 to be about 59% by age 50 and 87 % by age 70.

Another gene (BRCA2) has been implicated in hereditary breast cancer. This gene has been localized to a region on chromosome 13q12-q13.

Several families linked to BRCA2 show breast cancer in women as well as men, whereas no breast cancers in men have yet been observed in families linked to BRCA1.

The p53 gene also has been linked to breast cancer. This gene is a tumor suppresser gene which normally acts as a transcription factor that regulates the expression of other genes and has been mapped to chromosome 17p13.

A variety of different types of mutations in this gene have been found.

The OMIM morbidity map shows this and other cancer genes. Genes implicated in the cancer process are called oncogenes.

 

lA = aqua C = black G = gold T = Tea

The gene called BRCA1 actually contains instructions for four different proteins, IFP35, BRCA1, RHO7 and IFB35. These instructions are called exons. If you place your mouse on the image you can see these exons at the very top in the sorted version. The next region down with a regular pattern consists of noncoding DNA called ALU repeats. These make up 35% of the BRCA1 gene. These are the regions in the middle. The smeared appearance is due to deletion and point mutations that have occurred over the entire history of this gene.

by L. Van Warren (c) 2000 Warren Design Vision * All Rights Reserved