Transcript Overview of Genetics

Chapter 1
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Chapter 1 –DNA databases of
convicted felons have solved many
crimes and exonerated many innocent
people. What might be the benefits and
dangers of establishing databases on
everyone? How should such a program
be instituted?
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Is a life science
It is the study of inherited variation and
traits
Genes are the units of heredity
Genes are composed of
Deoxyribonucleic Acid (DNA)
Traits are produced by an interaction
between the genes and the environment
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Contain the instructions
within the cells for
protein production
The field of proteomics
studies the production
of proteins within
specific cell types.
Figure 1.1
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Is the complete set of genetic
information for an organism
It includes:
 All of the genes present in an organism
and
 Other DNA sequences that do not
encode genes
Human genome was sequenced in 2000
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Detects health-related genetic variants
May be used
 To prevent, delay, control, or treat
symptoms
 Gain information on risk of genetic
diseases and for pre-pregnancy testing
 Personalize medical treatment
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Figure 1.2
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Step 1 – Research and record family history
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Step 2 – Provide cell sample
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Step 3 – Isolate sample DNA and apply to
personalized microarrays
Step 4 – Calculate and communicate results
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Genetic counselor
recommends tests and
explains the findings from
the laboratory testing
Confidentiality is important
Laws prevent employers and
insurers from discriminating
against anyone based on
genetic information
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Cystic fibrosis
Certain cancers
 Breast, Colorectal, Prostate
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Inherited forms of Alzheimer's
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Type 2 diabetes
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Rheumatoid Arthritis
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Celiac Disease
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Restless Legs Syndrome
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Macular Degeneration
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A double stranded polymer consisting of a chain
of nucleotides
Deoxyribonucleotide components:
• Phosphate
• Sugar: Deoxyribose
• Base:
▪ Guanine
G
▪ Adenine
A
▪ Thymine
T
▪ Cytosine
C
The sequence of the bases code for the amino
acid sequence in a protein
Box Figure 1.1
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Single stranded polymer of
ribonucleotides
Ribonucleotides components:
• Phosphate
• Sugar: Ribose
• Base:
▪ Guanine G
▪ Adenine A
▪ Uracil U
▪ Cytosine C
Several types: mRNA, tRNA, &
rRNA
Uses information on DNA to
construct proteins
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Only 1.5% of the DNA in the human genome
encodes protein
Rest includes highly repeated sequences with
unknown functions known as STR’s or short
tandem repeats
Includes about 24,000 protein encoding genes
Cataloged in database
 Online Mendelian Inheritance in Man
(OMIM)
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Alleles are variants of
genes
They form by mutation
Mutations in sperm or
egg cells are passed on
to the next generation
May be positive,
negative, or neutral
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Polymorphisms are variations 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 and are
important as markers
Each SNP represents a
difference in a single DNA
building block, called a
nucleotide.
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Composed of DNA and protein
Found in the nucleus of the cell
Human cells have 46
chromosomes
22 pairs of autosomes
The sex chromosomes X and Y
 Females have two X
chromosomes
 Males have one X and a Y
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A Karyotype
is a chart of the chromosomes organized
by the size of the chromosome pairs.
Figure 1.3
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All cells with a nucleus in the
body contain the same
genetic information
 Differentiation causes cells
to differ in appearance and
function. This is controlled
by variation in gene
expression.
 Stem cells are less
specialized
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The genotype of an individual is the alleles
(genes) they carry
The phenotype is the visible trait:
 Dominant alleles are expressed if the individual
carries one or two copies of the allele
 Recessive alleles are only expressed if the
individual carries two copies of the allele
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The Family
•Pedigrees are
diagrams that
enable recessive &
dominant traits to
be followed through
individuals across
multiple generations
of a family
nheritance of traits
can be observed in
families.
Figure 1.3
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A Population
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Is a group of
interbreeding individuals
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The gene pool is the alleles
in a population
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Evolution is the changing
allelic frequencies in
populations over time.
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Figure 1.3
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Two random people share
approximately 99.9% of
their genome
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Concept of “race” as
defined by skin color is a
social, not a biological,
concept
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Studies indicates humans
arose in Africa and
migrated across the globe
with relatively little
change.
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Mendelian traits are determined
by a single gene
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Most traits are multifactorial
and not controlled by a single
gene. They are influenced by
more than one gene and the
environment
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Some illnesses may occur in
different forms: Mendelian,
multifactorial, and non-inherited
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The modifying effect of the environment on gene
action counters the idea of genetic determinism, which
is that an inherited trait is inevitable.
The idea that “we are our genes,” or such phrases as
“its in her DNA,” dismiss environmental influences.
In predictive testing for inherited disease, which
detects a disease-causing genotype in a person without
symptoms, results are presented as risks, rather than
foregone conclusions, because the environment can
modify gene expression.
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A woman might be told “You have a 45 percent chance of
developing this form of breast cancer,” not, “You will get
breast cancer.”
Genetic determinism may be harmful or helpful, depending
upon how we apply it.
As part of social policy, genetic determinism can be
disastrous. An assumption that one ethnic group is genetically
less intelligent than another can lead to lowered expectations
and/or fewer educational opportunities for those perceived
as biologically inferior.
Environment, in fact, has a huge impact on intellectual
development
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Absolute risk - the probability that an individual will
develop a condition or trait
Relative risk - the likelihood that an individual from
one group will develop a condition in comparison to
another group (usually the general population)
Empiric risk - risk determined by observing incidence
of a trait in the population
Risk factor - a situation that alters incidence of a
disease (or trait)
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Figure 1.7
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• Historical
• Common origins
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• Forensics
• Crime scene
evidence
• Victim
Identification
• Location of blood
relatives,
i.e., adoptions
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Health care:
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Prediction of disease
Development of
treatments
Family planning
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Agriculture:
 Crop & animal breeding
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Genetically modified
foods (GMO’s)
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Pest management
Figure 1.12
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