Lecture 6 - Chapter 6
Page 1: Pedigree Analysis Introduction
Discussion about Luke and a mention of a sister, implying family lineage and connection to Skywalker
Importance of genealogy and analyzing family backgrounds
Page 2: Weekly Class Plan
Today: Lecture on Chapter 6
Tuesday: Discussion for week 4
Wednesday: Focus on genetics in research and the Brenner paper
Friday: Homework related to Chapter 6
Sunday: Wikipedia check-in 1 (20 points) – requiring six trainings completed and evaluating an article
Monday: Exam 1
Tuesday: Group discussions on Wikipedia topics
Page 3: Dihybrid Cross Review
Interactions between two genes and their impact on phenotypic ratios:
No interaction: 9:3:3:1
Novel phenotypes: 9:3:3:1
Duplicate and novel: 9:6:1
Recessive epistasis: 9:4:3
Dominant epistasis: 12:3:1
Duplicate recessive epistasis: 9:7
Duplicate dominant epistasis: 15:1
Dominant and recessive epistasis: 13:3
Concept of genetic pathways: Understanding the difference between mutant phenotypes and their normal functions by analyzing double mutants
Page 4: Pedigree Analysis in Human Genetics
Learning Goals:
Utilize concordance measurements and adoption studies to compare genetic and environmental contributions to phenotypes
Create comprehensive pedigrees for traits and calculate genetic outcomes
Predict genetic trait nature from inheritance patterns observed in pedigrees
Discuss cytoplasmic and gender-linked inheritance patterns
Page 5: Complexity in Human Genetics
Human genetics presents more complexity compared to model organisms
Lack of true breeding or isogenic individuals
Difficulty in controlling matings
Overall abundance of data points complicating genetic analysis
Page 6: Genetics vs Environment
Inquiry into traits influenced by genetics, environment, or both
Difference between monozygotic (identical) and dizygotic (fraternal) twins
Dizygotic twins share about 50% genetic information
Concordance measures percentage of twins sharing the same phenotype, typically assessed through twin/adoption studies
Higher concordance in monozygotic twins indicates strong genetic influence; similar levels in dizygotic twins suggest environmental impact
Page 7: Understanding Concordance
Questions regarding factors not driven by genetics
Identifying numerical indicators for entirely genetic or entirely environmental diseases
Page 8: Insights from Adoption Studies
Adoption studies often involve children adopted as babies by unrelated individuals
Importance of gathering biological parent data, despite limiting study pool
Findings from such studies may indicate genetic influence if there's a discrepancy between outcomes in adoptive and biological contexts
Page 9: Pedigree Analysis - Individuals
Key symbols for individuals in pedigree charts:
Gender identification: Male, Female, Unspecified
Definitions:
Unaffected person
Affected person with the trait
Obligate carrier (carries the gene without expressing the trait)
Asymptomatic carrier (unaffected currently but can express trait later)
Proband (first affected family member observed by a geneticist)
Deceased person
Family history unknown
Page 10: Pedigree Analysis - Families
Description of a family with two girls and one boy in order of birth
Notation for adoption, twins, and consanguinity (relation between mating individuals)
Notations include different symbols and lines to indicate relationships
Page 11: Pedigree Analysis - Generations
Generational labeling: Roman numerals for generations, Arabic numerals for individuals within those generations
Identification focus: Who is circled in the pedigree
Page 12: Creating a Pedigree Example
Example of Todd and Jane planning a family linked to Tay Sachs disease (autosomal recessive)
Importance of constructing a complete pedigree and calculating the probability of disease in offspring
Page 13: Predicting Genetics via Pedigrees
Analysis of Fig 6.3 in the textbook focusing on:
Disease phenotype indicators in a pedigree
Generation skipping
Equal effects on males and females
Paternal transmission of traits
Page 14: Assumptions in Pedigree Analysis
Common patterns observed:
Diseases tend to inherit rather than arise as new mutations
Disease alleles typically rare
Phenotypes often linked to single genes with full penetrance
Use of OMIM (Online Mendelian Inheritance in Man) as a resource for genetic traits with vast databases
Page 15: Analyzing Inheritance Patterns
Examination of Fig 6.4 regarding inheritance patterns
Questions of skipping generations, equal gender distribution, and paternal transmission
Page 16: Sex-Linked Genes: Y Chromosome
Examination of inheritance patterns specific to the Y chromosome along with related analysis questions
Page 17: Sex-Linked Genes: X Chromosome
Similar to Y chromosome analysis but focuses on X-linked patterns
Page 18: Practice Questions on Inheritance Patterns
Engaging with practice scenarios to predict inheritance patterns and their characteristics
Page 19: More Practice on Inheritance Predictions
Continuation of practice exercises emphasizing inheritance patterns
Page 20: Cytoplasmic Inheritance
Majority of DNA is in chromosomal pairs, but mitochondria contain distinct DNA
Mitochondrial traits typically inherited from mothers, impacting both daughters and sons
Mitochondria distribution during cell division can be uneven, causing varying outcomes in progeny
Mitochondrial diseases impact approximately 1 in 5000 and can lead to severe health conditions
Page 21: Leber Hereditary Optic Neuropathy (LHON)
Characteristics of LHON linked to mitochondrial mutations:
Expected patterns of inheritance and disease presentation
Assessment query about true/false statements regarding the disease's inheritance patterns
Page 22: Review of LHON Patterns
Continued assessment and understanding of LHON characteristics through True/False disambiguation
Page 23: Characteristics Influenced by Sex
Insight into sex-influenced characteristics that show higher penetrance in one sex compared to the other
Examples illustrating autosomal versus X-linked resemblance
Page 24: Exploring More Sex-Influenced Traits
Analysis integrating X-linked analogies to sex-influenced characteristics across generations
Page 25: Sex-Limited Characteristics
Traits displayed exclusively by one sex, exemplified by precocious puberty (autosomal dominant)
Analysis of inheritance in male offspring versus female carriers
Page 26: Comparison of Genetic Definitions
Difference between sex-influenced, sex-limited, and sex-linked characteristics:
Sex-influenced and sex-limited traits are autosomal, whereas sex-linked traits reside on sex chromosomes
Page 27: Genetic Maternal Effect
Discussion of how maternal genetics influence offspring phenotypes prior to embryo DNA transcription
Example allele dominance (Dextral S+) impacting traits
Page 28: Genomic Imprinting Concept
Explanation of the significance of parental allele lineage in expressions of certain genes (Igf2).
Discussion on the resetting of DNA marks during gamete formation
Page 29: Genomic Imprinting Outcomes
Expected genetic outcomes when mating individuals with functional/nonfunctional Igf2 alleles
Page 30: Continuing Genomic Imprinting Outcomes
Expected outcomes in mating scenarios and potential offspring phenotypes
Page 31: Influence of Sex on Heredity
Summary of how various genetic phenomena define characteristics influenced by sex:
Sex-linked: Genes on sex chromosomes
Sex-influenced: Autosomal genes more expressed in one sex
Sex-limited: Autosomal traits expressed in only one sex
Genetic maternal effect: Determination by maternal genotype
Cytoplasmic inheritance: Largely inherited from one parent
Genomic imprinting: Expression affected by transmitting parent sex
Page 32: Practice Scenario on Inheritance
Evaluates probabilities of affected children from specific parental unions and genetic trait carriers
Page 33: Sample Issues with Practical Application
Scenario considerations regarding horn traits in male and female populations, and additional traits in the Lesser Whatsit species
Page 34: Pedigree Analysis Fig 6.7
Visual representation accompanying discussions, detailing affected individuals across generations
Page 35: Pedigree Analysis Fig 6.10
Final visual representation highlighting the generational impact of genetic diseases or traits