modes of inheritance

Question 1

what is the inheritance pattern of OCA-2

Answer 1

active OCA-2 (dominant) leads to more melanin in melanocytes

Question 2

3 things dominant autosomal disorders tend to be?

Answer 2

• gain of function
• insufficient
• dominant negative effect

Question 3

example of autosomal dominant disorder?

Answer 3

Huntington’s disease, brittle bones disease (osteogenesis imperfecta)

Question 4

mutation in Huntington’s disease?

Answer 4

expansion CAG repeat huntingtin

Question 5

symptoms of Huntington’s disease?

Answer 5

start at 30-50 years of age
difficulty concentrating, depression, stumping, involuntary jerking, problems swallowing

Question 6

result of mutation on huntingtin protein?

Answer 6

abnormal intracellular huntingtin protein aggregate gains a pathological function which is toxic to neurones, leading to cell death

Question 7

what are the characteristics of osteogenesis imperfecta?

Answer 7

bones break easily
hearing loss, breathing problems, short height, blue tinge to whites of eyes

group of disorders mainly affecting bones

Question 8

mutations leading to osteogenesis imperfecta?

Answer 8

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

Question 9

pattern of inheritance of autosomal recessive disorders?

Answer 9

horizontal

subsequent siblings of an affected child have a 1 in 4 chance of being affected

Question 10

cystic fibrosis characteristics

Answer 10

failure to thrive
defective chloride ion channel
impaired airway defence
more prone to resp. infections
digestive issues

Question 11

mutations leading to cf?

Answer 11

various mutations in the gene encoding the chloride ion channel- CFTR gene on chromosome 7

Question 12

result of mutated CFTR gene?

Answer 12

defective chloride ion channel
loss of function- or may be degraded faster/present in inadequate amounts

Question 13

how many genes on the X chromosome

Answer 13

1000-1300 genes

850 ish coding

Question 14

how many genes on the Y chromosome

Answer 14

150 genes
50-70 coding

Question 15

example of x linked disease

Answer 15

haemophilia

Question 16

x linked dominant affects which children?

Answer 16

all daughters of an affected father, no sons.
condition tends to be milder and more variable in females than males

Question 17

example of x linked dominant disease?

Answer 17

x-linked hypophosphatemia

Question 18

characteristics of x-linked hypophosphatemia?

Answer 18

PHEX gene mutation
Overproduction FGF21
FGF21 inhibits kidney phosphate reabsorption
kidney cannot retain phosphate

results in vitamin d-resistanCE rickets

Question 19

inheritance pattern of y linked disorders

Answer 19

affects only males and all sons of an affected father

vertical pedigree pattern

Question 20

example of a y-linked disorder

Answer 20

retinitis pigmentosa

Question 21

characteristics of retinitis pigmentosa

Answer 21

mutation in RPY gene
cells of retina produce defective protein

Question 22

inheritance pattern of mtDNA disorders

Answer 22

maternally inherited, vertical pedigree pattern

Question 23

what is the reason for the variability of mt diseases?

Answer 23

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

Question 24

why can mt DNA disorders develop with age?

Answer 24

the accumulation of mutant mitochondria

Question 25

examples of mitochondrial disease

Answer 25

Leber’s hereditary optic neuropathy