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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 environmentthe 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 Nondiscrimination (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 adultonset 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?