Human Genetics 4
Course Announcements
Discussion & Quiz
There will be a quiz at the start of the discussion covering previous lectures.
Students are encouraged to bring a laptop or tablet with the lockdown browser pre-installed and functioning.
Students are reminded that they have already taken a quiz requiring this setup.
There is a free example quiz available that can be used to test the functionality of the lockdown browser.
Students can find this example quiz in D2L or directly through the instructor's class materials.
Class Activities
A case study on exome and whole genome sequencing related to diseases will be conducted during this discussion.
Students will also engage in partner discussions to facilitate learning.
Topic Overview
Mendelian Genetics
Introduction to Mendelian genetics as a continuation of the material in Chapter One.
Focus on the significance of genetic information in DNA profiling and organisms in environmental sequencing.
Understanding Traits
Definition of a Trait
A trait is often synonymous with a phenotype, describing observable characteristics of an organism (e.g., tall vs. short, round vs. wrinkled, blue eyes vs. brown eyes).
The concept of traits was introduced by Gregor Mendel, who investigated the transmission of traits through genes.
Types of Traits
Mendelian Traits
Traits that are largely determined by a single gene.
Examples of Mendelian genetic diseases include:
Huntington's Disease: Involves the Huntington gene.
Sickle Cell Anemia: Linked to the hemoglobin mutation gene.
Tay Sachs Disease: Encoded by a single gene.
Complex Traits
Traits that are influenced by multiple genes and environmental factors, making prediction of occurrence more challenging.
Example: Colon Cancer is difficult to predict due to its genetic complexity and environmental impacts.
In contrast, prediction of Tay Sachs Disease is straightforward through gene sequencing due to it being a single-gene trait.
Examples of Complex Traits
Eye Color:
Determined by approximately sixteen genes, each contributing variably to the final phenotype (e.g., one gene may contribute 50% and another 5%).
Can be predicted using whole-genome sequencing despite not all contributing genes being known as of now.
Polydactyly:
A genetic condition that can be expressed through single or multiple genes.
Noted examples include polydactyl cats bred for their extra digits.
The condition can manifest with extreme variations, such as entire additional paws.
Cell Differentiation and Stem Cells
Human Cell Composition
The human body consists of approximately eukaryotic cells.
Includes a vast number of non-human cells, primarily bacteria, which outnumber human cells.
Stem Cells and Differentiation
Stem cells undergo differentiation to form specialized cells through the gene expression process (transcription and translation).
Different types of stem cells:
Totipotent: Can develop into an entire organism (e.g., fertilized egg).
Pluripotent: Capable of forming all tissue types but not a whole organism.
Multipotent: Limited in differentiation potential (e.g., neural stem cells).
Unipotent: Can only develop into one type of cell.
Importance of Gene Expression in Differentiation
Differential gene expression leads to the formation of various cell types, such as bone or muscle cells.
The process of differentiation is essential for developmental biology, as it defines the specialization of cells.
Gene Interaction and Heredity
Mendel's Contribution
Introduced concepts of genotype (genetic makeup) vs. phenotype (observable traits) in the mid-1800s.
Lack of molecular understanding at the time regarding genes and chromosomes.
Genotype vs. Phenotype
Genotype: Combinations of alleles (e.g., Aa, AA, aa) affecting traits.
Phenotype: The physical manifestation of the genotype (e.g., tall or short).
Genetic Relationships
Understanding familial relationships through genetic connection:
Parents: 50% shared genetics.
Grandparents: 25% shared genetics.
Siblings: Average is 50% shared, but can vary.
Uncles/Aunts: 25% shared with nieces/nephews.
First cousins: About 12.5%.
Independent Assortment and Variation
Genetic variation arises from independent assortment and recombination during meiosis.
Genetic testing and sequencing can assist in understanding these percentages and relationships more accurately than before.
Population Genetics
Gene Pool Definition
The gene pool in a population encompasses all the alleles for a particular gene in that population.
Important for statistical understanding of traits and diseases affecting them (e.g., predicting incidence of diseases like Tay Sachs or colon cancer).
Gathering Genetic Data
Genetic data can be collected from populations to understand health trends and guide public health strategies.
The significance of things like ancestry and tracing genetic predispositions contributes to overall society and health insights.
Ethical Implications of Genetics
Ethical Dilemmas
The implications of genetic testing can lead to ethical questions about individuals knowing their genetic predispositions (e.g., breast cancer risk).
Students will engage with these ethical discussions throughout the course, addressing varying personal views and professional stances on genetic knowledge and its implications.
Personal Perspectives
Different individuals may have varying levels of comfort with genetic data.
The instructor notes a personal inclination to pursue information, raising questions about the ethical balance between data knowledge and individual choices.
Applications of Genetic Testing
Real-World Use of DNA Profiling
DNA profiling can facilitate ancestry research and determine biological relationships (e.g., paternity tests available in consumer markets).
Implications for identifying victims in disasters (e.g., 9/11) have reinforced the need for improved genetic sequencing techniques.
Food Authenticity Testing
Genetic testing can help ensure the authenticity of food items, thereby tackling fraudulent product sales in gourmet food markets.