GENETICS - Inheritance types Flashcards
What are the X-linked dominant conditions? (3)
- Aicardi syndrome
- Incontinentia pigmentii
- Alport’s syndrome
Which chromosome defect is associated with retinoblastoma?
Rb gene located on long arm chromosome 13
What diseases are examples of mitrochondrial inheritance? (6)
- Lebers hereditary optic atrophy
- Mitochondrial encephalopathy, lactic acidosis and stroke (MELAS)
- Myoclonus epilepsy associated with ragged-red fibres (MERRF)
- Kearns-Sayre syndrome (KSS)
- Pearson syndrome
- Diabetes/Deafness
Consanguinity is more likely to have which type of inheritance?
Recessive
What is X-linked inheritance?
mode of inheritance in which a mutation in a gene on the X chromosome causes the phenotype to be always expressed in males
and in females who are homozygous for the gene mutation
What are the patterns of inheritance in X-linked? (3)
- Father cannot pass X-linked disease to son as father always passes Y chromosome –> means mother of X-linked male always is responsible.
- More commonly expressed in males than females.
- Skips generations - affected grandfather will not have an affected son, but could have an affected grandson through his daughter
How can some female heterozygotes be affected in X-linked inheritance?
Lyonisation - inactivation of one of the two X chromosomes in every somatic cell.
What is the inactived X chromosome known as in lyonisation?
The Barr Body
What are the most common X-linked ocular diseases (8)
- Red-Green colour blindness
- Duchennes muscular dystrophy
- Fabry Disease
- Lowe Syndrome
- Ocular albinism
- Retinitis pigmentosa
- Choroideraemia
- Retinoschisis
What does mitochondrial DNA encode for?
Encodes for tRNA and ribosome RNA for mitochondrial protein synthesis
Why does mitochondrial DNA have a higher mutation rate than nuclear DNA? (5)
- DNA polymerases are more inaccurate
- mtDNA more suspectible to oxidative damage.
- Alkylating agents affect mtDNA more
- repair mechanisms underdeveloped
- No introns - likely impact a coding sequence if mutation arises.
What are the main inheritance patterns for mitochondrial inheritance? (3)
- Males cannot transmit
- Both males/females affected if mother has defective gene
- An affected mother passes defect to all children but only daughters will trasmit.
What is the mode of inheritance of chromatopsia?
X-linked recessive.