Detection of Hereditary Breast Cancer - PowerPoint Presentation

Slide1

Detection of Hereditary Breast CancerSlide2

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 cancerSlide3

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)Slide4

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 JenniferSlide5
Slide6

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 deletionSlide7

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 chromosomeSlide8

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 functionSlide9

STR for BRCA 2

Location = chromosome 13

STR analysis for this lab

It is on 13, next to BRCA 2 geneSlide10

Gel Electrophoresis

Different STRs have different repeats…

Gel will separate alleles based on number of repeats

More repeats travels less

Less repeats travels moreSlide11

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 ControlSlide12
Slide13
Slide14

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 dyeSlide15

Calculate the Rf

value

Distance

the DNA fragment has migrated from the origin (gel well)

R

f

=

Distance from the origin (gel well) to the

reference

point (tracking dye)Slide16

DNA Size Markers

Fragment Length in Base Pairs

Distance Migrated (mm)

A

Distance to Reference Point (mm)

B

R

f

A ÷ B

Fragment 1

1353

Fragment 2

1078

Fragment 3

872

Fragment 4

603

Fragment 5

310

Fragment 6281   Fragment 7234   Fragment 8194   Slide17

DNA Sample:

Fragment:

Distance Migrated (mm)

A

Distance to Reference Point (mm)

B

R

f

A ÷ B

Diana

Fragment 1

Fragment 2

Jennifer

Fragment 1

Fragment 2

Laura

Fragment 1

Fragment 2

  JudyFragment 1   Fragment 2   Slide18

DNA Sample:

Fragment:

Fragment Length (in base pairs)

Allele Present:

Diana

Fragment 1

Fragment 2

Jennifer

Fragment 1

Fragment 2

Laura

Fragment 1

Fragment 2

Judy

Fragment 1

Fragment 2

 Slide19

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 9Slide20

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.