JM

biology - inheritance and pedigre lecture 9

Class Structure and Examination Information

  • No Business Week: Due to upcoming midterm scheduled a week from today.

  • Quiz Availability:

    • A quiz was posted last week covering inheritance.

    • Pedigree practice questions available on Moodle, along with answers.

  • Review Opportunities:

    • Textbook contains review questions.

    • Online resources available through the textbook website, including quizzes.

Midterm Examination Details

  • Date and Location:

    • Midterm is in-class during the regular scheduled class time on October 6.

  • Online Requirement:

    • Students must bring laptops.

    • Examination will be conducted via the Safe Exam Browser.

  • Exam Structure:

    • Total of 40 questions, objective-style.

    • Expected to finish well ahead of class time.

    • Question types include:

    • Multiple choice.

    • True/False questions.

    • Fill-in-the-blank and diagram labeling.

  • Materials Required:

    • Laptop and power cord.

Course Content Overview

  • Previous Classes Covered:

    • Life cycles and inheritance.

    • Focus on finalizing concepts in inheritance this class and possibly next class.

  • Topics Discussed Last Class:

    • Overlaying Mendelian principles with chromosome behavior.

    • Concepts of dominant and recessive genes located on chromosomes.

  • Key Mendelian Principles:

    • Independent Assortment: Genes segregate during meiotic events.

    • Segregation of Alleles: Dominant and recessive alleles determine trait expression.

    • Linkage: Genes in close proximity on chromosomes may not assort independently.

Inheritance and Pedigrees

  • Mendelian Inheritance:

    • Discussed through examples such as cystic fibrosis related to CTFR gene.

    • Individuals homozygous for the recessive CF allele express cystic fibrosis, producing excessive mucus affecting lungs and digestive systems.

  • Carrier Identification:

    • Heterozygous individuals are carriers and do not express disease symptoms.

  • Pedigrees:

    • Used to track inheritance patterns through generations.

    • Layout includes:

    • Circles: Females.

    • Squares: Males.

    • Horizontal Lines: Indicate mating between individuals.

    • Symbols in pedigrees include:

    • Shaded shapes: Affected individuals.

    • Unshaded shapes: Unaffected individuals.

    • Half-shaded shapes: Carriers (presumed heterozygotes).

Genetic Disease Examples

  • Cystic Fibrosis:

    • Recessive allele leads to severe symptoms.

    • Salt content in sweat is a key diagnostic test.

  • Huntington’s Disease:

    • Autosomal dominant inheritance; one copy of the dominant allele results in disease expression.

    • Caused by mutations affecting a protein called huntingtin, leading to neurodegeneration due to proteins being misfolded through excessive glutamine repeats (more than 36).

  • Pedigree Analysis for Huntington's Disease:

    • Affected individuals can be homozygous dominant or heterozygous.

    • Mode of inheritance can be observed in generational patterns.

Sex Chromosomes and Inheritance Variations

  • Sex Chromosome Systems:

    • XY System: Males (XY), Females (XX). Human X chromosome carries about 950-1,000 genes; Y chromosome has about 65-100 genes.

    • ZW System: In birds, males (ZZ) have similar chromosomes while females (ZW) have different chromosomes.

    • XO System: Certain insects, where females have XX chromosomes and males have X.

    • Haplodiploidy: In bees, fertilized eggs develop into diploid females, while unfertilized eggs develop into haploid males.

Temperature-Dependent Sex Determination

  • In species like alligators, eggs develop as females at temperatures below 30°C and as males above 34°C, impacting population dynamics.

  • Climate Change Implications: Rising temperatures may skew sex ratios in species depending on temperature for sex determination.

Pleiotropy and Multiple Gene Interaction

  • Pleiotropy: One gene affects multiple phenotypical traits; cystic fibrosis is a notable example affecting multiple organs.

  • Incomplete Dominance vs. Codominance:

    • Incomplete Dominance: Phenotype of heterozygotes is distinct from both homozygotes (e.g., pink flowers from red and white parents).

    • Codominance: Interaction among alleles where both contribute to phenotype (e.g., blood types A and B).

Blood Types and Antigen Functionality

  • ABO Blood Group: The presence/absence of antigens on red blood cell surfaces determines blood type; relevant for blood transfusions.

    • Type O: Universal donor (no antigens present).

    • Type AB: Universal recipient (no antibodies against A or B antigens).

    • Type A/B: Have respective antibodies that attack differing antigens, complicating transfusions.

Genetic Research and Findings

  • Recent studies suggested correlations between blood types and susceptibility to diseases like COVID-19; further research needed.

  • Additional studies highlighted Neanderthal DNA variants affecting COVID-19 susceptibility.

Conclusion

  • Continued study will involve exploring blood typing in further class sessions, including potential implications and discoveries in genetics.

Following Topics in Next Classes

  • Further discussion on inheritance patterns.

  • Review more examples concerning blood types and related traits.

  • Discussion of genetic counseling based on familial history relating to recessive traits.