R11 single gene inheritance Flashcards
What is a x-linked recessive inheritance ?
Mutant occurs on the y chromosome as there is only one copy of the gene, wild type present on the X
What do the square, circles, lateral lines, vertical lines, number inside a shape, shaded shape, half-shaded shape, dot in the middle and cross through mean on a pedigree diagram ?
- Males are square boxes
- Females are circles
- Lateral link show mating
- Line downwards shows offspring
- Number inside the square or circle shows number of offspring
- Affected are coloured in shape
- Heterozygous for autosomal recessive are half shaded
- Dot in the middle show’s carrier for sex-linked recessive
- Cross through the shape shows death
What does an autosomal dominant pedigree look like ?
Affected individuals in all generations, both sexes affected, only one copy of abnormal allele is required
What does Autosomal recessive pedigree look like ?
Most generations unaffected, affects siblings of both sexes, parents are heterozygous and unaffected
parents may be consanguineous (cousins)-shown by double lateral lines in the same tree
What does an X-linked dominant pedigree look like ?
Not common, appears in all generations, affected father passes to a daughter, heterozygous mother passes condition onto both son and daughter
What does an X-linked recessive pedigree look like ?
Appears to jump a generation, mostly males affected, females can be heterozygotic carriers
How are linked genes denoted ?
AB/ab
The slash denotes homologous chromosomes
How are unlinked genes denoted ?
A/a ; B/b
semicolon represents space, could just be a spacebar too
How is unknown linkage genes denoted ?
A/a * B/b
What are some main differences in mendelian traits vs complex traits ?
Mendelian - single-gene, discrete traits, no environmental influences, predictable pattern, rare in humans
Complex traits - multi-factorial inheritance, continuous variation, environmental influence, less predictable patterns, common in humans
