Complex Disorders Intro
- Created by: Former Member
- Created on: 21-10-19 09:36
Chromosomal Abnormalities
Changes in visible alteration of chromosome or abnormality produced by chromosomal abnormalities e.g. reduction of chromosome number during meiosis
1. Numerical
- Triploid/tetraploid - lethal and not compatible with animal life
- Aneuploidy - extra copy of one or more chromosomes due to nondisjunction during meiosis and can be compatible with animal life e.g. trisomy 21 results in Down's Syndrome
2. Structural
- deletion
- duplication
- translocation - one part of chromosome moves to another) e.g. philedelphia (chr 9-22)
- inversion -part on chromosome is reversed, occurs when undergoes breakage and rearranges within itself. Can be paracentric or pericentric
If occurs in egg/sperm = constitutional abnormality = all cells
If occurs later in life = somatic abnormalities = some cells (mosaicism)
Mendelian Disorders
- Rare, monogenic (caused by single gene),
- Mendelian inheritance - recessive, dominant or sex linked,
- Doesn't include de novo mutations or mosaics
- High penetrance - prophylactic intervention
- Environment effect weak but mutation effect can be modulated by common genetic variant and environmental factors e.g. diet
Gene mutation:
- Point Mutation - e.g. sickle cell anaemia mutation in HBB. Silent, missense (changes amino acid), nonsense (change to stop codon)
- Deletion - e.g. cystic fibrosis deletion in CFTR
- Insertion - e.g. Huntington's disease CAG repeated up to x120
1.Somatic (body) cells - not transmitted to progeny (acquired mutation) but can cause malignant transformation and congenital diseases
2. Gamete cells (germ cells) - transmitted to progeny (inherited mutation) can give rise to inherited disease
Mendel's Laws
Not valid for multifactorial complex disease
Law of Segregation - during gamete formation, the 2 alleles for each gene (locus) segregate from each other so that each gamete carries only one allele for each gene (locus)
Law of Independent Assortment - Alleles for different traits separate independently during the formation of gametes
Law of Dominance - Some alleles…
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