Chapt01 Lecture

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Human Genetics Concepts and Applications

Seventh Edition

Powerpoint Lecture Outline

Ricki Lewis

Prepared byMary King KananenPenn State AltoonaEdited RP Fall 2007


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Overview of Genetics Chapter 1


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Genetics

•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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Genes

• Contain the instructions within the cells for protein production

Figure 1.1


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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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Genetic Testing

• Uses new technology• 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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Steps in Genetic Testing

Figure 1.2


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Genetic Counseling

• 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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Examples of Genetic Tests

• Cystic fibrosis

• Certain cancers

• Inherited forms of Alzheimer's

• Type 2 diabetes

• Others


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Levels of Genetics

Figure 1.3


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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 AThymine T Cytosine C

•The sequence of the bases code for the amino acid sequence in a protein


1-12Box Figure 1.1


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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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Box Figure 1.2


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Genome

• 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 – Online Mendelian Inheritance in Man (OMIM)


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Genes

• 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

• Examples


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Variations

• 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


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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


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Levels of Organization

• Cells

• Tissues

• Organs

• Organ systems

• Organism


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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 1.3


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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 1.3


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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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•Two random people share approximately 99.9% of their genome

•Concept of “race” as defined by skin color is a social, not a biological, concept

•Studies indicates humans arose in Africa and migrated across the globe with relatively little change.

Variation in the Human Population


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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 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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Genetic Risk

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 observingincidence of a trait in the population

Risk factor a situation that alters incidence of a disease (or trait)


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Relative Risk

Figure 1.7


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DNA profiling compares DNA sequences to

•Establish relationships

•Forensics

•Biobanks

Applications of Genetics

Box Table 1.1


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• Historical

• Common origins

Figure 1.9


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Health care

• Prediction of disease

• Development of treatments

• Family planning


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Agriculture • Crop and animal

breeding• Genetically modified

foods• Pest management

Figure 1.12


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• Ecology

Technology

Chapt01 Lecture