1. Detection of Hereditary Breast Cancer

2. Breast Cancer Genes
Two genes associated with inheritance of breast cancer
Breast cancer gene 1 (BRCA1) – Chromosome 17
BRCA 2 – Chromosome 13
When normal…
Both are tumor suppressor genes
Repair damage and prevent cancer cells from forming
When mutated…
Lead to breast or ovarian cancer

3. BRCA 1 and BRCA 2
5 to 10% of all breast cancers are because of these genes
Women…
12% chance of developing breast cancer in lifetime
Goes up to 85% if said woman has mutated BRCA 1 or 2
If male has BRCA 2 mutation
1 in 10 ratio of getting breast cancer (100,000 jump)

4. Family Members Judy is worried!!!!! Jennifer has DNA sequencing…
Jennifer had breast cancer
Test positive of BRCA 2 (negative for BRCA 1)
Laura
Tests positive for same mutation as Jennifer

6. BRCA2 We will be looking at BRCA2 Contains 80,000 nucleotides
600 mutations associated with BRCA2
Most cause increased incidence of breast cancer (not all)
Most of these mutations are insertion or deletion

7. Marker Analysis (Haplotyping)
Due to expense of DNA sequencing…
We will use marker analysis to test Jennifer and Diana
Marker analysis…
Genetic test
Gene mutation is analyzed using a genetic marker
Instead of analyzing genet itself
Genetic marker: short sequence of DNA associated with a particular gene or trait with a known location on a chromosome

8. Short Tandem Repeats
Genetic markers used in marker analysis are short DNA sequences
Also called microsatellites
STR = region of DNA composed of a short sequence of nucleotides repeated many times.
Number of repeated STRs varies from person to person
Different number of repeats = different alleles
Most occur in introns (non-coding DNA)
Do not affect gene function

9. STR for BRCA 2 Location = chromosome 13 STR analysis for this lab
It is on 13, next to BRCA 2 gene

10. Gel Electrophoresis Different STRs have different repeats…
Gel will separate alleles based on number of repeats
More repeats travels less
Less repeats travels more

11. Loading Samples 5 uL: 130 Volts for 30 minutes
Lane #1: DNA Size Markers
Lane #2: Helen’s DNA
Lane #3: Harold’s DNA
Lane #4: Susan’s DNA
Lane #5: Adam’s DNA
Lane #6: Negative Control

14. Determining Size of DNA Fragment
Using a ruler
Measure (ON EACH BAND!!!!)
Distance of DNA fragment from origin (gel well)
Distance from the origin (gel well) to the tracking dye

15. Calculate the Rf value
Distance the DNA fragment has migrated from the origin (gel well)
Rf = Distance from the origin (gel well) to the reference point (tracking dye)

16. Fragment Length in Base Pairs Distance Migrated (mm) A
DNA Size Markers
Fragment Length in Base Pairs
Distance Migrated (mm) A
Distance to Reference Point (mm) B Rf
A ÷ B
Fragment 1
1353
Fragment 2
1078
Fragment 3
872
Fragment 4
603
Fragment 5
310
Fragment 6
281
Fragment 7
234
Fragment 8
194

17. Distance to Reference Point (mm)
DNA Sample:
Fragment:
Distance Migrated (mm) A
Distance to Reference Point (mm) B Rf
A ÷ B
Diana
Fragment 1
Fragment 2
Jennifer
Laura
Judy

18. DNA Sample:
Fragment:
Fragment Length (in base pairs)
Allele Present:
Diana
Fragment 1
Fragment 2
Jennifer
Laura
Judy

19. Fragment Length in Base Pairs:
Allele:
200
Allele 1
300
Allele 2
400
Allele 3
500
Allele 4
600
Allele 5
700
Allele 6
800
Allele 7
900
Allele 8
1000
Allele 9

20. Questions
Which allele is associated with the BRCA2 mutation? Explain your answer.
Which family members have the BRCA2 mutation? Explain your answer.
Explain whether you think Judy’s family occurrences of breast and ovarian cancers are sporadic, hereditary, or familial.
Is Judy a good candidate for BRCA1 or BRCA2 genetic testing? Explain your answer.