Lisa Sardinia, J.D., Ph.D.Associate Professor, Pacific University

Associate Director, Pacific Institute for Ethics & Social Policy

Genetic Testing: Do You Really Want to Know What’s in Your

Genes?

What are the types of genetic testing?

• Diagnostic• Predictive• Carrier• Newborn• Prenatal• Pre-implantation• Forensic

Diagnostic Genetic Testing

• identify or rule out a specific genetic or chromosomal condition

• often used to confirm a diagnosis based on physical signs and symptoms

congenital myotonic dystrophy

hemochromatosis

Predictive Genetic Testing

• detects gene mutations associated with disorders that appear later in life

• frequently provides a probability, not a certainty, that a disorder will occur

familial adenomatous polyposis

ApoE4 & Alzheimer’s Disease

Carrier Screening

• identifies people who carry one copy of a gene mutation that, when present in two copies, causes a genetic disorder

• provides info on a couple’s risk of having a child with a genetic disorder

Newborn Screening

• used just after birth to identify genetic disorders that can be treated early in life

• All states test for phenylketonuria & congenital hypothyroidism

• Oregon tests for 34 disorders

Prenatal Genetic Testing

• used to detect genetic or chromosomal disorders in a fetus during pregnancy

• hundreds of tests available--few are routine

Preimplantation Genetic Diagnosis

• detects genetic changes in embryos produced by IVF

• testing done prior to implantation/pregnancy

Forensic DNA Testing

• uses DNA sequences to identify an individual for legal purposes

• not used to detect gene mutations associated with a disease

How is genetic testing done?

We need to make a short digression here….

What is a gene?

• basic physical & functional unit of heredity

• made up of DNA• composed of subunits

called bases (A, C, G, T)• vary in size from a few

hundred DNA bases to more than 2 million bases

• The Human Genome Project has estimated that humans have between 20,000 and 25,000 genes

Where are genes?

• In every cell, wound up to form chromosomes

What does a gene do?

• contains instructions to build all the proteins that make our bodies function

• passes genetic information to offspring

For example…

• Red blood cells transport oxygen throughout our bodies using a protein called hemoglobin

• If the hemoglobin gene is normal, the instructions will be used to make a normal hemoglobin protein

• But if the instructions are changed, or mutated, changes in the hemoglobin protein could result

• One such mutation causes the disorder sickle cell anemia

Genes can be inherited…

Back to genetic testing

• the goal is to provide information about a person’s genes and chromosomes, including gene variants that can result in disorders

So, once again, how is genetic testing done?

• Tissues tested include:– blood– skin– cheek cells– hair follicles– embryonic cells– placental tissue– amniotic fluid

Methods of Genetic Testing

• Cytogenetic analysis

• DNA Analysis

Cytogenetic Analysis

normal karyotype trisomy 21Down syndrome

FISH

DNA Analysis

DNA Analysis

Complications….

Carrier frequency of cystic fibrosis

Ethnicity Carrier frequency

Caucasian (non-Hispanic) 1/25

Ashkenazi Jewish 1/25

Hispanic American 1/46

African American 1/65

CF carrier risk after a negative result for 32 mutations

Ethnicity Carrier frequency

Caucasian (non-Hispanic) 1/240

Ashkenazi Jewish 1/800

Hispanic American 1/146-1/167

African American 1/207

Tricky stuff--Predictive genetic testing

Trickier stuff--Predictive genetic testing….

with probabilities

• Cancer• Alzheimer’s disease• Type II diabetes

Cancer

Two-hit hypothesis

Alzheimer’s disease:Apolipoprotein E

Type II diabetes:Genome-wide association study

I am my genome

https://www.23andme.com/

http://www.navigenics.com/

http://www.decodeme.com/

http://www.personalgenomes.org/

http://jimwatsonsequence.cshl.edu/cgi-perl/gbrowse/jwsequence/

Brave new world?http://www.txfertility.com/ivf-program/pgs.html

Want more?

Pacific Institute for Ethics & Social Policy

Fall Programming

Genetic Testing: Science—Ethics—Public Policy

•Community seminars (September-November)

•Town Hall panel discussion (November 18th)

http://www.pacificu.eduhttp://www.pacificu.edu