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Powerpoint Lecture Outline
Human Genetics
Concepts and Applications
Eighth Edition
Ricki Lewis
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Chapter 1
Overview of Genetics
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Genetics
• Is a life science
• Is the study of inherited variation and traits
• Some traits are determined nearly entirely by genes ;
most traits have environmental components
•Complete set of genetic information characteristic of
an organism, including protein-encoding genes and
other DNA sequences, constitutes a Genome
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The Genome
• 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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Genes
• Contain the instructions
within the cells for protein
production
• Genes are the units of
heredity
• Genes are composed of
Deoxyribonucleic Acid
(DNA)
Figure 1.1
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Genomics
• considers many genes at a time , in contrast to
the emphasis on single-gene
traits that was 20the Century Genetics
addresses the more common illnesses influenced
by many genes that interact with each other and
the environment
Compare ourselves to other speciesmyostatin mutation in human, cattle, chickens –
very similar
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Genetic Testing
• Young people might take genetic tests to prevent,
delay, control, or treat symptoms that are likely to
develop, or to gain information, perhaps to help
decide whether to have children
• Example Mackenzie and Laurel
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Procedure…………….
• DNA extracted, cut into pieces , tagged with
fluorescent molecules and applied to “DNA chips”,
postage sized chips of glass or nylon. Genes are
aligned in fixed positions, this device is technically
called a “microarray”. A typical microarray bears
hundreds or thousands of DNA pieces.
• “Expression panel” can determine which genes are
turned on or off in the affected cells from the tumor
or from blood
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DNA Expression microarrays……..
• useful in diagnosing and treating
cancer (can show the response to a
particular drug, side effects)
• Test results always kept confidential
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Levels of Genetics
Figure 1.2
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Deoxyribonucleic Acid (DNA)
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
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Reading1.1, Figure 1
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Ribonucleic Acid (RNA)
• Single stranded polymer of ribonucleotides
• Ribonucleotides components:
• Phosphate
• Sugar: Ribose
• Base:
Guanine G
Adenine A
Uracil
U
Cytosine C
• Several types
• Uses information on DNA to construct proteins
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Reading 1.1, Figure 2
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Proteomics
• Considers the types of proteins made in a
particular type of cell (24,000 protein encoding
genes)
• Only 1.5% of the DNA in the human genome
encodes protein
• Rest includes highly repeated sequences with
unknown functions
• Includes about 24,000 protein encoding genes
• Cataloged in database
– Mendelian Inheritance in Man (MIM)
– RNA interference(RNA i) actually controls
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which proteins a cell manufactures
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Genes
• Alleles are variants of genes
• mutation causes changes in a DNA sequence
• Mutations in sperm or egg cells are passed on to
the next generation
• May be positive, negative, or neutral
• Examples
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Variations
• Polymorphisms(many forms) 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 (millions
identified) individuals and are important as
markers
• Identification of exclusive SNPs combinations
allow the identification of a particular disorder
and estimation of disease risk
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Chromosomes
•
•
•
•
•
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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Cells
• 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 and can
become many different cell types
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Levels of Organization
•
•
•
•
•
Cells
Tissues
Organs
Organ systems
Organism
Figure 1.4
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Individual
• The genotype of an individual is the alleles
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
• Inheritance of traits
can be observed in
families.
• A pedigree
indicates the
structure of a family
schematically.
Figure 1.4
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A Population
• Is a group of interbreeding
individuals
• The gene pool is the
alleles in a population
• Evolution is the changing
allelic frequencies in
populations over time.
Figure 1.4
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Evolution
• Comparison of DNA
sequences indicates the
amount of similarity between
two species.
• 98% of human DNA
sequences are shared with
chimpanzees.
• Humans share genes with
mice, fish, fruit flies, yeast,
and bacteria.
Figure 1.5
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Review of Genetic Terms
Table 1.1
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Most Genes Do Not Function Alone
• Mendelian traits are determined by a single
gene
• Most traits are multifactorial(complex traits)
and not controlled by a single gene. They are
influenced by more than one gene and the
environment
• Some illnesses may occur in different forms:
Mendelian, multifactorial, and non-inherited
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Genes and Disease Risk
• Mendelian traits have simple inheritance
• Multifactorial traits more complicated
– BRCA1 gene and breast cancer
– less than 5% cases of breast cancer
Ethnic influences as well as environmental
Ashkenazim
• Knowing risk can help us make good choices
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Statistics Represent Risks
• Risk assessment estimates the degree to which a
particular event or situation endangers a population
• event is the likelihood of inheriting a particular gene
or gene combination
• Absolute risk is the probability that an individual
will develop a particular condition
• Relative risk is the likelihood that an individual
from a particular population will develop a condition
compared with individuals from another group
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Applications of Genetics
• Forensics
Identifying victims, DNA at crime scenes,
overturning convictions, adoptions
• Rewriting history
Thomas Jefferson offspring, the Jewish
Lemba
• Common ancestry
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Figure 1.10
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Applications of Genetics
Health care
• Prediction of disease
– Genetic testing, concerns over privacy
• Development of treatments
• Family planning
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Applications of Genetics
Agriculture
• Biotechnology
• Crop and animal breeding
• Genetically modified foods
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Applications of Genetics
• Ecology
– Metagenomics – sequencing DNA from a
targeted habitat
– Exaample: Sargasso Sea, an body
• Global perspective and human health
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