Topic 12 pt 1: Pedigree analysis Flashcards
Why are humans terrible organisms to study from a genetics perspective
- can’t selectively mate
- too few offspring
- long generation time
- few discrete traits
What is a pedigree
Pictorial representation of a family history; a family tree that outlines the inheritance of one or more characteristics
What is a proband
The person from whom the pedigree is initiated
Slide 6***
Pedigree symbols
What should we keep in mind when carrying out a pedigree analysis
- Genetic disorders are rare
- Mendelian ratios are rarely seen
- Non-family members are assumed to be homozygous normal (WT)
- Recessive disorders more common (not phenotypically visible; het)
What is the different between a disorder and a variant
Disorder = individuals are affected or not affected
Variants = more common
What are the four key observations made when doing pedigree analysis
- Are the affected individuals in each generation
- Are there sex-differences between affected individuals
- Is there male to male transmission
- Do unaffected parents have affected offspring
Slide 8***
important
Characteristics of an autosomal recessive trait
- appears in both sexes equally
- skips generations
- affected offspring born to unaffected parents
Answers to four questions in autosomal recessive trait
- No (recessive)
- No (autosomal)
- Not sure
- Yes (recessive)
Example of autosomal recessive trait. Describe it
Cystic fibrosis
- common, fatal
- build-up of mucus in the lungs
- digestive problems
Characteristics of an autosomal dominant trait
- both sexes equally
- both sexes transmit to offspring
- does not skip generations
- affected offspring have affected parent
Example of autosomal dominant trait
Hereditary dwarfism (achondroplasia)
