Human Genetics

Overview

What are Genes?

• Genes contain the instructions within the cells for protein production

• Genes are composed of deoxyribonucleic acid (DNA)

• Traits are produced by an interaction between the genes and their environment- the human phenotype.

Genetic Variation

• Alleles are variants of genes

• They form by mutation

• Mutations in sperm or egg cells are passed on to the next generation

• Mutations may be positive, negative, or neutral

Genetic Variation

• Polymorphisms are variations (alleles) in the DNA sequence that occur in at least 1% of the population

• Single nucleotide polymorphisms (SNPs) are single base sites that differ among individuals

- Can cause disease or act as genomic markers

What is the Genome?

• The complete set of genetic information for an organism

• It includes all of the genes present in an organism and also DNA sequences that do not encode genes.

• Genomics is a field that analyzes and compares genomes of different species

The Human Genome

• Only 1.5% of our DNA encodes protein

- About 20,325 protein-encoding genes in all • Rest of the human genome includes highly

repeated sequences with unknown functions• Genes known to cause disorders or traits are

cataloged in a database

- Online Mendelian Inheritance in Man (OMIM)• Proteomics is a field that studies the proteins

made in a cell

Effects of Mutations depends on Gene Expression

Human Genetics Presents Challenges

• Can’t set up genetic crosses so we rely on natural genetic experiments.

• Use of pedigrees

• Statistics and heritability studies

• Genome Wide Association Studies

A pedigree is a diagram used to study traits in families

Genetic Testing and Treatment

• Tests to identify about 1,200 single-gene disorders have been available for years- Direct-to-consumer (DTC) genetic testing

• The Genetic Information Non-discrimination (GINA) act was passed in the US in 2008

• Genome information is useful for developing treatment to genetic and infectious diseases

Genetic Testing• Examine a person's DNA - taken from cells in a sample

of blood for some anomaly that flags a disease or disorder.

• The DNA change can be relatively large: a missing or added piece of a chromosome - even an entire chromosome.

• The change can be extremely small, as little as one extra, missing, or altered chemical base.

• Genes can be over-expressed, inactivated, or lost altogether.

• Pieces of chromosomes become switched, or transposed, so that a gene ends up in a location where it is permanently and inappropriately turned on or off.

Ethical Issues for Genetic Testing

• Privacy and confidentiality of genetic information. – Who owns and controls

genetic information? Is genetic privacy different from medical privacy?

Privacy and Confidentiality of Genetic Information

• The Genetic Information Nondiscrimination Act (GINA) became law on May 21, 2008.

• GINA prohibits U.S. health insurance companies and employers from discrimination on the basis of information derived from genetic tests.

• In addition, insurers and employers are not allowed under the law to request or demand a genetic test.

Ethical Issues for Genetic Testing

• Fairness in the use of genetic information by insurers, employers, courts, schools, adoption agencies, and the military, among others.

• Who should have access to personal genetic information, and how will it be used?

Ethical Issues for Genetic Testing

• Psychological impact, stigmatization, and discrimination due to an individual’s genetic makeup.

• How does personal genetic information affect self-identity and society’s perceptions?

Ethical Issues for Genetic Testing

• Reproductive issues including adequate and informed consent and the use of genetic information in reproductive decision making.

• Do healthcare personnel properly counsel parents about risks and limitations? What larger societal issues are raised by new reproductive technologies?

Ethical Issues for Genetic Testing

• Clinical issues including the education of doctors and other health-service providers, people identified with genetic conditions, and the general public; and implementation of standards and quality-control measures.

• How should health professionals be prepared for the new genetics?

• How can the public be educated to make informed choices?

• How will genetic tests be evaluated and regulated for accuracy, reliability, and usefulness?

• How does society balance current scientific limitations and social risk with long-term benefits?

Ethical Issues for Genetic Testing

• Fairness in access to advanced genomic technologies.

• Who will benefit? Will there be major worldwide inequities?

Ethical Issues for Genetic Testing

• Uncertainties associated with gene tests for susceptibilities and complex conditions. Should testing be performed when no treatment is available or when interpretation is unsure? Should children be tested for susceptibility to adult-onset diseases?

Ethical Issues for Genetic Testing

• Conceptual and philosophical implications regarding human responsibility, free will vs genetic determinism, and understanding of health and disease.

• Do our genes influence our behavior, and can we control it? What is considered acceptable diversity? Where is the line drawn between medical treatment and enhancement?

Ethical Issues for Genetic Testing

• Commercialization of products including property rights (patents, copyrights, and trade secrets) and accessibility of data and materials.

• Will patenting DNA sequences limit their accessibility and development?