Human Genetics
Mariam55Ch 19: Genetic Technologies: Patenting, Modifying, and Monitoring DNA
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Biotechnology
use or alteration of cells or biological molecules for specific applications
agriculture selectively breeds plants for food
transgenic organisms have DNA from different species
recombinant DNA comes from more than one type of organism
gene expression is possible because of the universality of the genetic code
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What is Patentable?
new, useful, and non-obvious
so, how does this apply to DNA?
patent law has to keep up with biotechnology
DNA sequence alone does not have patent protection
useful as a tool for research
new or improved product
such as a diagnostic test or drug
non-obvious discovery not previously known
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Technology Timeline
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Modifying DNA
recombinant DNA technology
recombines genes from one organism to genome of another
e.g., human genes in bacteria to produce peptides and proteins useful as drugs
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Recombinant DNA Technology
“gene cloning” to make copies of one gene
relies on bacterial restriction enzyme specificity
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Creating Recombinant DNA Molecules
uses a cloning vector
for recombinant DNA
carries DNA from cells of one species into cells of another
commonly used vectors include:
plasmids
bacteriophages
disabled retroviruses
bacterial and yeast artificial chromosomes
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Recombinant DNA
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Selecting Recombinant Molecules
recombinant (+) cells survive selection
cells that contain plasmids with foreign genes
recombinant (-) cells do not survive
cells that lack plasmids
cells with plasmids that do not contain genes
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Applications of Recombinant DNA
biochemical properties of protein
genetic pathways of protein
mass-produce proteins (e.g., insulin)
conventional methods are sometimes better choice because of economics
e.g., textile industry produces indigo dye in E. coli with glucose pathway and genes from another bacterium
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Transgenic Organisms
efficient expression of recombinant genes
in body fluids of transgenic animal
limitations to bacterial protein expression
transgenic sheep, cows, and goats
express human genes in their milk
clotting factors
anticoagulants
collagen
antibodies
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Transgenic Organisms
insertion of DNA into cells
chemicals that open holes in plasma membrane
liposomes that carry DNA into cells
transposon-mediated insertion
retroviral/adenoviral delivery
embryonic stem cell/ somatic cell nuclear transfer
for heterozygous dominant, cloned goat is ready for production
for homozygous recessive, cloned goat must be selectively bred
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Animal Models
transgenic animals are more useful as models of human diseases
e.g., insertion of mutant human beta globin gene that causes sickle-cell anemia into mice
testing on animal models before testing on humans
significant side effects prevent human trials
study of disease pathology, progression
limited to animal phenotypes
human-specific traits
transgene insertion position effects
mouse model of Huntington disease
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Genetically Modified Foods
genetic modification based on phenotype
Genetically Modified Organisms– genetically altered to have a specific phenotype
selective breeding
transgenic organism
genetically engineered organism
not natural selection
effects on ecosystems
loss of genetic diversity
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Bioremediation
transgenic organisms can provide processes
bioremediation
use of bacteria or plants to detoxify pollutants
e.g.,
Nickel-contaminated soils
Mercury-tainted soils
Trinitrotoluene (TNT) in land mines
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Monitoring Gene Function
microarrays (gene chips) detect gene expression
mRNAs from a cell type on microchip
experiment compares two samples of CSF: spinal cord injury and uninjured control
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Gene Expression Profiling Chronicles Repair After Spinal Cord Injury
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Gene Silencing and Genome Editing
gene silencing
blocks synthesis of or degrades mRNA
genome editing
creates double-stranded breaks in the DNA
inserts or removes DNA sequence
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Gene silencing: RNA Interference
RNA molecules can fold into short, double-stranded regions where the base sequence is complementary
separates dsRNA into single strands
single strand binds to mRNA, blocks translation
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Gene silencing: Antisense Sequences
antisense-induced exon skipping
silences mutations that cause exons to be cut out of maturing mRNA
short, synthetic DNA morpholinos
complementary or “antisense” to splicing mutation
original mutation is bypassed
production of full-length protein
mutation in Duchenne muscular dystrophy, X-linked recessive disorder, cause exon 52 skipping resulting in frameshift to nonsense
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Ch 20:
Genetic Testing and Treatment
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Genetic Counseling
upon diagnosis of genetic condition
addresses medical, psychological, sociological, and ethical issues
genetic counselor is a health care professional
helps patients and their families learn about genetic testing and or diagnosis
pediatrics, prenatal care, specialty
modes of inheritance
disease risks and symptoms
tests and treatments
coordination of care
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Genetic Testing
administered at all ages for variety of reasons
identify mutations to help diagnose and choose treatment
new tests arise every year
“personal genome”
genetic admixture
unknown parentage
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Newborn Screening
state-administered programs
usually tests for inborn errors of metabolism
not all genetic tests
tandem mass spectrometry
identify unusual metabolites or chemical imbalances
e.g., Guthrie test for PKU detects phenylalanine
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Genetic Testing of Children
chromosomal microarray (CMA) test detects very small deletions and duplications that are associated with:
Autism
Developmental delay
Intellectual disability
Behavioral problems
Other phenotypes
performed after abnormal karyotype result
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Genetic Testing of Adults
diagnostic workup based on symptoms
gene specific
faster DNA sequencing has lowered the cost
direct-to-consumer testing
non-medical phenotypes: athleticism, etc.
controlled by CLIA (clinical laboratory improvement amendments), but not regulated
medical advice cannot be given without licensed doctor of genetics
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DTC: Nutrigenetics Testing
genetic tests with questionnaires about diet, exercise, and lifestyle habits
“nutrigenetics” profile with dietary suggestions
pitches to purchase supplements
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Matching Patient to Drug
pharmacogenetic testing
detects single gene variant that affects drug metabolism
pharmacogenomic testing
detects variants of multiple genes or gene expression patterns that affect drug metabolism
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Treating Genetic Disease
treating the phenotype
removing an affected body part
replacing an affected body part or biochemical with material from a donor
delivering pure, human proteins derived from recombinant DNA technology to compensate for the effects of a mutation
refolding correctly a misfolded protein
gene therapy, to replace mutant alleles
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Treating The Phenotype
inborn errors of metabolism
treatment based on metabolic pathway
if any enzyme is deficient or its activity blocked, the substrate builds up and the product is deficient
approaches for counteracting these diseases
replace enzyme
reduce substrate
correct enzyme
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E.g., Lysosomal Storage Disease
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Gene Therapy: correcting the enzyme
working copies of genes to specific cell types
typically delivered through modified viruses
traditionally on rare single-gene disorders
no treatment available, risk less than reward
e.g., adenosine deaminase deficiency (ADA)
successful correction of ADA deficiency in T cells through gene therapy
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First Gene Therapy Patient
30 individuals have been treated successfully as of 2005 with ADA replacement gene therapy
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Some Sites of Gene Therapy
endothelium
secretes proteins directly into bloodstream
muscle
accessible, comprises ½ body mass and has a good blood supply
liver
many functions and can regenerate
lungs
easily accessed with aerosol spray
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Gene Therapy: correcting the enzyme
OTC (Ornithine Transcarbamylase) deficiency
X-linked recessive mutation
OTC breaks down amino acids present in protein
OTC deficiency allows buildup of ammonia, which damages brain function
treated with low-protein diet, ammonia-binding drugs
gene therapy with adenovirus developed
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OTC Gene Therapy
toxicity of adenoviral infection caused death after 4 days
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Gene Therapy: correct the enzyme
Leber’s Congenital Amaurosis II
severe form of blindness, autosomal recessive
RPE65 gene mutation
gene therapy
sheepdog with same mutation
four young adults
8-year old Corey Haas
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Ch 21: Reproductive Technologies
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Savior Siblings and More
innovations in conception
advertising for an attractive, athletic woman oocyte donor
storing oocytes before cancer therapy to become pregnant once healthy
removing sperm from a paralyzed man and injecting into oocyte
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Savior Siblings and More
alternative reasons for conception
sibling as stem cell donor
sibling as organ donor
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Assisted Reproductive Technologies
methods that allow conception
replace the source of gamete
aid fertilization
provide a healthy uterus
genetic screening
U.S. Government does not regulate ARTs
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Infertility and Subfertility
infertility – inability to conceive a child
after a year of frequent intercourse without contraceptives
subfertility– couples who can conceive
require longer time than usual
commonly affects one in six couples
physical cause identified in 90% of cases: 30% in males, 60% in females
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Male Infertility
easier to detect, often harder to treat
four in 100 men are infertile
most cases of male infertility are genetic (Y chm)
azoospermia
low sperm count (oligospermia)
malfunctioning immune system
varicose vein in the scrotum
structural sperm defects
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Female Infertility
any part of the female reproductive system
irregular menstrual cycles are sign of infertility
difficult to pinpoint ovulation
hormonal imbalances:
tumor in ovary or pituitary
underactive thyroid
steroid drugs use
inactive or absent ovaries:
use egg donor
inactive or absent uterus:
use surrogate
blocked uterine tubes:
ectopic pregnancy
blocked uterus:
fibroids
endometriosis
hostile secretions:
vaginal and cervix
anti-spermy
genomic errors:
aneuploidy loss
spontaneous abortion
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Infertility Tests
man is tested first
easier, less costly, and less painful
sperm count, motility, and morphology
female reproductive organs tested
present and functioning correctly
psychological evaluation
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Assisted Reproductive Technologies
Intrauterine insemination (IUI)
Surrogate motherhood
In vitro fertilization (IVF)
Gamete intrafallopian transfer (GIFT)
Zygote intrafallopian transfer (ZIFT)
Oocyte banking and donation
Preimplantation genetic diagnosis (PGD)
Sequential polar body analysis
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Landmarks in Reproductive Technology
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Landmarks in Reproductive Technology (2)
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Landmarks in Reproductive Technology (3)
intracytoplasmic sperm injection
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Preimplantation Genetic Diagnosis (PGD)
allows detection of genetic and chromosomal abnormalities prior to implantation
preimplantation embryo is tested at a stage prior to when it would implant in the uterus
one cell of an 8-celled embryo
remaining cells complete normal development
about 29% success rate
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Some Assisted Reproductive Technologies
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Sequential Polar Body Analysis
genetic information earlier in development
infers absence of mutation in a fertilized ovum
second polar body should be the same
separation of sister chromatids in meiosis II
technology is still experimental:
follow up with PGD
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Sometimes ARTs leave “extra” oocytes, fertilized ova, or very early embryos
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