Mendelian inheritance & Genetic basis of complex Inheritance

Question 1

• Describe the characteristics of Medelian Inheritance, both autosomal and sex-linked.

Answer 1

• Autosomal
  
  • Dominant
    
    • Each generation is affected
    • Both sexes affected in equal proportion
    • Equally transmitted by both sexes
    • Transmitted through affected individuals
    • 50% chance of inheriting mutation (Only need 1 dominant allele)
  • Recessive
    
    • Affected individuals in a single generation
    • Generations “skipped”
    • Both sexes affected in equal proportions

Question 2

• Describe the characteristics of Medelian Inheritance, both autosomal and sex-linked.

Answer 2

• Sex Linkage
  
  • X-Linked Recessive
    
    • Males affected more than females, who have 2 copies of the X Chromosomes (hope for a dominant allele)
    • Transmitted through affected/unaffected females
    • Males cannot transmit disorders to sons
    • Daughters of affected males will be carriers
  • X-Linked Dominant
    
    • Both sexes affected
    • Females usually less severely affected than males
    • Affected males cannot transmit disorder to their sons
    • Daughters of affected males will be affected
  • Y-Linked
    
    • Affects males only

Question 3

Anticipation- Triplet Repeat Expansion

Answer 3

Anticipation: Disease presents at earlier age and/or increasing severity in succeeding generations.

Triplet repeat diseases:

• Huntington’s disease
• Myotonic dystrophy (muscle wasting)
• Fragile X syndrome (learning disabilities and cognitive impairment)

Question 4

Homoplasmy and Heteroplasmy

Answer 4

Polyploidy: up to thousands mitochondria per cell.

Polyploid cells and organisms are those containing more than 2 homologous pair sets of chromosomes.

2 - 10 copies per mitochondrion.

Question 5

Genetic modifiers

Answer 5

Genes that have small quantitative effects on the level of expression of another gene. May involve polymorphism.