Dr. C. Young
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Human Genetics: Concepts and Applications
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Ricki Lewis
7th edition
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Syllabus
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Website
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Other stuff
What’s so special about genetics?
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“… [P]ublic dialogue hasn’t even begun to seriously consider how radically genetic technologies will alter human life and society …
My bet is that feasible technologies to retool human life will put us face to face with the basic dilemma of deciding what it means to be human within two decades.”
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Steven Quartz, philosophy professor at Cal Tech, in the online publication
Edge (2000)
 is the study of inherited variations and traits
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DNA
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Genes
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Chromosomes
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Genome
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Individual
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Family
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Population

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 are the basic unit of inheritance. are composed of DNA (deoxyribonucleic acid).
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 direct the production of proteins. are responsible for individual traits.
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Genetic traits can vary from superficial and harmless to global and fatal.
Different versions of the same gene are called alleles.
Alleles result from the mutations in the DNA.
What changes have occurred in the DNA to cause this new trait?
is the complete set of genetic information characteristic of the organism. consists of all of the genes present in an organism and other
DNA that does not encode genes.
How do different DNA changes affect the cell?
 consists of ~3 billion base pairs of DNA.
 includes ~27,000 genes.
 is organized as 23 pairs of chromosomes.
DNA is organized in discrete segments called chromosomes.
Humans have 23 pairs of chromosomes:
22 autosome pairs which are the same in both sexes
1 pair of sex chromosomes (X or Y).
Each chromosome includes hundreds/thousands of different genes.

is a diagram of the chromosomes organized by the size of the chromosome pairs.
 carry two alleles of each gene.
Genotype is the combination of alleles that an individual possesses.
Phenotype is the visible trait that results from a particular genotype.
How do the altered cells affect the whole body?
Somatic cells comprise the majority of an individual’s body.
During development distinct types of cells make proteins using different subsets of genes.
Germline cells within the testis or ovary produce gametes (sperm or ova).
Germline cells retain the ability to form all of the types of cells, both germline and somatic cells.
The inheritance of traits can be observed in families.
A pedigree depicts the structure of a family schematically.
is a group of interbreeding individuals who possess a particular collection of alleles or gene pool.
Population genetics looks at the prevalence of certain alleles in the population.
How common is the allele?
How common is it in certain ethnic groups, regions of the world, by gender, etc.?

Comparison of DNA sequences indicates the amount of similarity between two species.
>98% of human DNA sequences are shared with the chimpanzee.
Many genes present in humans are also present in mice, fish, fruit flies, yeast, and bacteria.
Very similar
On average two random people share the same DNA sequence in
99.9% of their genome.
Studies of variation among humans indicates humans arose in
Africa and migrated across the globe with relatively little change. but also very different
On average two random people differ at 3 million base pairs
(approximately one nucleotide of every thousand).
Some traits are determined predominantly by one gene.
Mendelian traits result from variation in the alleles of one gene.
Other traits are determined by multiple genes.
Polygenic traits result from variation in several genes.
Still other traits are determined by genes and the environment.
Multifactorial traits result from the effects of one or more genes and the environment.

Identity forensics paternity testing
Health care prediction of disease development of treatments family planning
Agriculture crop and animal breeding genetically modified foods pest management
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“Pie Could Be Robbery Clue: Burglary Ruins Family Christmas.”
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Liverpool Echo, December 24, 2002.
“Suspect identified by sweat.”
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The New Zealand Herald, January 11, 2003.
“Fingered By Socks.”
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The Mirror, January 13, 2003.
“Crook Trapped by Dandruff.”
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Daily Star, February 13, 2003.
“Suspects get snared by a relatives DNA.”
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USA Today, June 8, 2005.
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 the incidence of a trait in the population
Risk factor - a situation that alters the incidence of a disease (or trait)
Genetically modified foods
“Golden rice” modified by the addition of the beta carotene gene, a precursor of vitamin A, stores more iron than unmodified rice.