Chapter 22: Genetic Testing and Treatment

What services and types of information does a genetic counselor provide?

-Provide information on modes of inheritance, disease risks & symptoms, available tests & treatments

-Interpret direct-to-consumer genetic tests & assist other healthcare professionals w/ genetic information on their practices

How are the services that a genetic counselor provides different from those of a nurse or a physician?

While a genetic counselor provides genetic-based information for the client and works with the patient to deliberate and necessary tests and care, nurses or physicians focus more on a broader aspect of medical care in order to treat specific illnesses or diagnoses.

What are some reasons for prenatal genetic testing

Tests to see if embryo has genetic abnormalities, defects, or anomalies

What are some reasons for newborn genetic testing

-Usually tests for inborn errors of metabolism

-Identifies unusual metabolites or chemical imbalances that indicate disease via chemistry

What is the first genetic test that was created for newborns

Guthrie test for PKA

What are some reasons for children genetic testing

detects very small deletion and duplications that are associated with:

Autism spectrum disorder

Developmental delay

What are some reasons for adult genetic testing

detect risk of developing cancer

family planning

What are some of the issues associated with direct-to-consumer testing for inborn athletic ability

Tests are too simplistic

Testing for a single gene is not enough, you need access to resources, training, and facilities with equipment

What are some of the issues associated with direct-to-consumer testing for nutrigenetics

Companies were "scamming" consumers with inaccurate information and making pitches to purchase costly supplements

What is a Pharmacogenetic test

detects a variant of a single gene that affects drug metabolism

What is Pharmacogenomic test

detects variants of multiple genes or gene expression patterns that affect drug metabolism

Advantages of using pharmacogenetics and pharmacogenomics to select the best drugs for patients

-Identify patients likely to have adverse reaction

-Select drug most likely to be effective

-Monitor response to drug treatment

-Predict course of illness (prognosis)

Treatments of genetic diseases

-Removing affected body part (amputation)

-Replacing affected body part or biochemical with material from a donor (transplantation)

-Delivering pure, human proteins derived from recombinant DNA technology

-Refolding correctly a misfolded protein Blocking gene expression (gene silencing)

-Using gene therapy to add wild type alleles without removing mutant alleles

-Using gene editing and genome editing to replace, delete, or add alleles

Ex-vivo therapy

applied to cells outside of body that are then returned via IV infusion or into spinal fluid

In-vivo therapy

applied directly to an interior body part through catheter inserted and snaked into appropriate organ

Is ex-vivo therapy or in-vivo therapy more invasive

in-vivo

Describe adenosine deaminase (ADA) deficiency

-Can cause severe combined immune deficiency (SCID)

Describe what happened with Ashanthi DeSilva and adenosine deaminase (ADA) deficiency

Leukocytes (WBCs) harvested and redesigned to harbor functional ADA genes > reinserted back to her (ex-vivo) gene therapy- doing well!

Describe ornithine transcarbamylase (OTC) deficiency

Causes build upon ammonia > brain function is affected

Describe what happened with Jesse Gelsinger and ornithine transcarbamylase (OTC) deficiency

Treated using adenovirus vector into his liver > liver failure, high hemoglobin, and elevated ammonia > brain dead 🙁

Germline gene therapy

gamete or zygote alteration heritable changes; NOT done in humans; transgenic organisms (usually)

Somatic gene therapy

corrects only the cells that the disease affects; NOT heritable

Why is CRISPR-Cas 9 considered a possible replacement for gene therapy?

More precise type of gene therapy

-Delivers a gene to a specific part of genome, and can also replace, remove, or add a gene.

-Can act at multiple precise sites in the genome.

Gene therapy

adds correct DNA sequences may insert into a chromosome at random or remain outside (episome)

Gene editing

corrects DNA sequences by adding, deleting, or replacing DNA at mutation site