modes of inheritance Flashcards
(25 cards)
what is the inheritance pattern of OCA-2
active OCA-2 (dominant) leads to more melanin in melanocytes
3 things dominant autosomal disorders tend to be?
- gain of function
- insufficient
- dominant negative effect
example of autosomal dominant disorder?
Huntington’s disease, brittle bones disease (osteogenesis imperfecta)
mutation in Huntington’s disease?
expansion CAG repeat huntingtin
symptoms of Huntington’s disease?
start at 30-50 years of age
difficulty concentrating, depression, stumping, involuntary jerking, problems swallowing
result of mutation on huntingtin protein?
abnormal intracellular huntingtin protein aggregate gains a pathological function which is toxic to neurones, leading to cell death
what are the characteristics of osteogenesis imperfecta?
bones break easily
hearing loss, breathing problems, short height, blue tinge to whites of eyes
group of disorders mainly affecting bones
mutations leading to osteogenesis imperfecta?
type 1- insufficient quantities of collagen
type 2, 3 and 4- mutation of collagen results in altered structure + interference of function of the normal protein
pattern of inheritance of autosomal recessive disorders?
horizontal
subsequent siblings of an affected child have a 1 in 4 chance of being affected
cystic fibrosis characteristics
failure to thrive
defective chloride ion channel
impaired airway defence
more prone to resp. infections
digestive issues
mutations leading to cf?
various mutations in the gene encoding the chloride ion channel- CFTR gene on chromosome 7
result of mutated CFTR gene?
defective chloride ion channel
loss of function- or may be degraded faster/present in inadequate amounts
how many genes on the X chromosome
1000-1300 genes
850 ish coding
how many genes on the Y chromosome
150 genes
50-70 coding
example of x linked disease
haemophilia
x linked dominant affects which children?
all daughters of an affected father, no sons.
condition tends to be milder and more variable in females than males
example of x linked dominant disease?
x-linked hypophosphatemia
characteristics of x-linked hypophosphatemia?
PHEX gene mutation
Overproduction FGF21
FGF21 inhibits kidney phosphate reabsorption
kidney cannot retain phosphate
results in vitamin d-resistanCE rickets
inheritance pattern of y linked disorders
affects only males and all sons of an affected father
vertical pedigree pattern
example of a y-linked disorder
retinitis pigmentosa
characteristics of retinitis pigmentosa
mutation in RPY gene
cells of retina produce defective protein
inheritance pattern of mtDNA disorders
maternally inherited, vertical pedigree pattern
what is the reason for the variability of mt diseases?
mitochondria have multiple genome copies- some are normal, some are mutant (heteroplasmy)
disease is only expressed above a threshold
mt can gain or lose stated genes
why can mt DNA disorders develop with age?
the accumulation of mutant mitochondria
