k38 genetic counseling-2012.ppt

8/10/2019 k38 GENETIC COUNSELING-2012.ppt

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Genetic Counseling

Genetic counseling is the process of prov id ingindiv iduals and fami l ies w ith informat ion on the

nature, inheritance, and impl icat ions of g enetic

disorders to help them make informed medical and

personal decis ions. It deals with genet ic r isk assessment and the use of

fam i ly history and genet ic test ing to clar i fy genet ic

status for fami ly members.

This is not meant to address all personal, cultural, orethical issues that individuals may face or to substitutefor consultation with a genetics professional


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Genetic Counseling

What does it mean if a disorder seems to

run in my family?.

What are the different ways in whicha

genetic conditions can be inherited? If a genetic disorder runs in my family, what

are the chances that my children will have

the condition?

Why aresome genetic conditions more

common in particular ethnic groups?


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Breast Cancer genes


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Breast Cancer genes

Gene

symbol

Chromosomal

Locus

Protein Name

BRCA1 17q21 Breast cancer type 1susceptibility protein

BRCA2 13q12.3 Breast cancer type 2susceptibility protein


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Disease characteristics

Mutations in BRCA1or BRCA2predispose tobreast cancerand ovarian cancer as well asprostate cancer (BRCA1)and other cancers(BRCA2).

The risk of developing cancerthat isassociated with a BRCA1or BRCA2cancer-predisposing mutation is not known andappears to bevariable even within familiesofsimilar ethnic background with the samemutation.


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Disease characteristics

Estimatesof breast cancer and ovarian cancerrisks have been derived from families withmultiple affected individualsas well as fromfamilies with few affected individualsand frompopulation-basedstudies.

Prognosis for breast cancer survivaldependsupon the stage at which breast cancer isdiagnosed. Prognosis for individuals withBRCA1or BRCA2cancer-predisposingmutations may not be different from that forcontrols.


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Diagnosis/testing

Molecular genetic testing: for probands whoare identified to be at high riskfor a BRCA1orBRCA2cancer-predisposing mutation and forat-risk relativesof an individual with anidentified BRCA1or BRCA2cancer-predisposing mutation.

No currently available technique canguarantee the identification of all cancer-predisposing mutations in the BRCA1gene orin the BRCA2gene.


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Cumulative Risk of Breast Cancer by Age in Women from

Families with Cancer-Predisposing Mutations

AgeCumulative Risk

BRCA1 BRCA2

30 yrs 3.2% 4.6%

40 yrs 19.1% 12%

50 yrs 50.8% 46%

60 yrs 54.2% 61%

70 yrs 85% 86%


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How do people inherit breast cancer?

Most cases of breast cancer are not

inherited but are associated with genetic

changes that occur only in breast cancer

cells(somatic mutations) and occurduring a person's lifetime.

In hereditary breast cancer, the way that

cancer risk is inherited depends on thegene involved.


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Genetic testing

Genetic testing for breast cancer can

have a huge impacton the lives of those

tested.

Before being tested, a person must sign

an informed-consent document,which

states that she or he has been fully

informed of the benefits and risksoftesting.


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Genetic Counseling

After you receive your test result, it is

important to have a genetic counseloror

other qualified health care professional

interpret the result and discuss yourhealth managementoptions with you.

This will make it easier for you to talk

with your other doctors, who will help youmake decisions about how best to

address your cancer risks.


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Genetic counseling

Consist of:

Cancer-predisposing mutations in the

BRCA1and BRCA2genes are inherited

in an autosomal dominant manner.

Each offspring of an individual with a

BRCA1or BRCA2cancer-predisposing

mutation has a 50% chance of inheriting

the mutation.


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Genetic counseling

Molecular genetic testing ofasymptomatic family members at risk ofinheriting either a BRCA1or BRCA2cancer-predisposing mutation is possibleonce the family-specific mutation hasbeen identified.

Prenatal testing is possible for

pregnancies at increased risk; however,requests for prenatal diagnosis of adult-onset diseases are uncommon andrequire careful genetic counseling.


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Genetic counseling

If one family member has an abnormal breast

cancer gene, it does not mean that all family

members will have it.

Suppose either your mother or father has aBRCA1 or BRCA2 abnormality. Your risk of

inheriting the abnormal gene is 50%. Each of

your children has a 25% chance of inheriting

the abnormal gene

50% of your 50% risk(as long as the children's father does not have

an abnormal gene).


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Genetics clinics

are a source of information for

individuals and families regarding the

natural history, treatment, mode of

inheritance, and genetic risks to otherfamily members as well as information

about available consumer-oriented

resources


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Pedigree


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Pedigree


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Pedigree


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Pedigree


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Colorectal Cancer


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Colorectal Cancer


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Colorectal Cancer


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Genotypes


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Allele frequency

k38 genetic counseling-2012.ppt

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