Complex inheritance Flashcards
1
Q
Examples of non-Mendelian inheritance
A
- Gene conversion
- Incomplete penetrance
- Genomic inprinting
- Extranuclear inheritance
- Anticipation
2
Q
Inheritance penetrance
A
Mechanisms: environmental factor, genetic modifiers
3
Q
Genomic imprint mechanisms
A
- An epigenetic process
- Variants from parents, dependent on that parent
- Genes expressed from only one chromosome
- If an inherited allele from a parent is imprinted, it is silenced
- Only the allele from the other parent is expressed
4
Q
Genomic imprinting can result in
A
- Deletions
- Point mutations
- Imprinting errors
- Uniparental disomy
5
Q
Imprinting errors examples
A
- Angelman and Prader-Willi, same chromosomal region. Totally different syndromes
6
Q
Angelman syndrome
A
- Epilepsy
- Severe mental retardation
- Awkward gait
- Inappropriate laughter
- Deletion on maternal chromosome or paternal UPD
7
Q
Prader-Willi Syndrome
A
- Hypotonia
- Mental retardation (mild to moderate)
- Short stature
- Obesity
- Deletion on paternal side or maternal UPD
8
Q
Uniparental disomy
A
- Inheritance of a chromosome pair from one parental origin
9
Q
Effects of uniparental diploidy
A
- Gynogenic: 2 maternal genomes, mass of embryo, ovarian teratoma
- Androgenic: 2 paternal genomes, mass of placenta, molar pregnancy
10
Q
Extranuclear inheritance
A
Mechanism:
- Mitochondria mutation due to higher mutation rate in mitochondria
- Lack of efficient DNA repair
- Lack of protective proteins, histones
- Damaged by free radicals
11
Q
3 major myopathies
A
- Myoclonic epilpepsy with ragged red fibres (MEERF)
- Mitochondrial myopathy, encephalomyopathy, lactic acidosis, stroke-like symptoms (MELAS)
- Chronic progressive external opthalomoplegia (CPEO)
12
Q
Non-myopathic diseases from extranuclear inheritance
A
- Leber’s hereditary optic neuropathy - loss of central vision
- Leigh’s syndrome - encephalopathy
- Diabetes mellitus and deafness (DAD)
13
Q
Anticipation
A
Mechanism:
- Triplet repeat expansion
- Disease present at earlier age and/or increasing severity in succeeding generations
e. d. Huntington’s, Myotonic dystrophy, Fragile X syndrome
14
Q
Genetic penetrance definition
A
- Frequency with which a trait is manifested by individuals carry the gene
15
Q
Cystic fibrosis
A
- Autosomal recessive
- CF phenotype is variable in terms of severity and affected organs
- Genetic modifiers: may involve polymorphism
- Environmental factors: lifestyle, diet, smoking, alcohol/drugs, stress, air pollution, infection
