Genetic Inheritance Flashcards
What does mitochondrial DNA code for.
How is it inherited?
Codes for 15 proteins, rRNA, some tRNA
most encoded by genome, small amount by mitochondria itself
From mother
What is Dominant autosomal inheritance?
Dominant characteristic will manifest as phenotype in a heterozygote.
Why are brown eyes dominant?
Gene responsible -
OCA-2
It controls the amount of melanin in melanocytes.
Active OCA-2 leads to melanin build up
What is the chance of dominant autosomal disorders affecting offspring?
1/2
vertical pedigree pattern
Can be gain of function, dominant negative effect, insufficient
What are the symptoms of Huntington’s disease?
What mutation is it due to?
( Dominant )
Start age 30-50
Difficulty concentrating, depression, stumbling, involuntary jerking, problems swallowing
Due to DNA expansion of CAG repeat on chromosome 4 resulting in protein aggregation and causes neuronal function issues - toxic to neurons
What are the symptoms of Osteogenesis imperfecta?
What mutations can it be caused by?
( Dominant )
Bones break easily, hearing loss, breathing problems, short height, blue tinge to whites of eyes
Type I - insufficient collagen
Type II,II,IV - abnormal protein with altered structure interferes with function of normal protein
Why are carriers of Autosomal Recessive disorders unaffected?
They have lost a single copy of a gene but the normal one is sufficient to maintain normal function
Each subsequent sibling of an autosomal recessive disorder child has a (a) chance of being affected?
1/4
horizontal pedigree pattern
both parents have to be carriers
What are the symptoms of Cystic Fibrosis?
What makes the characteristic of the disorder recessive?
Failure to thrive
Defective chloride ion channel
Impaired airway defence
Digestive issues
Chloride ion channel mutations - CFTR gene on chromosome 7.
Need both copies to result it complete mutant CFTR channels
Loss of function affect
How many genes make up the X and Y chromosome and how many proteins can each code respectively?
1000-1300 genes, code for 850 proteins
150 genes, code for 50-70 proteins
Who do X-linked disorders effect? (recessive)
Mainly males, effectively dominant to them as one gene on X chromosome will show trait.
Females who are homozygous will also have condition
Parents and children to affected ppl are normally unaffected
example - haemophilia - different levels of severity, in some diseases females can give subtle signs of the disease as carriers e.g. fabrys
( X linked recessive ) brothers of an affected son have (a) chance of (b) Sisters have (c) chance of (d)
a - 1/2
b - having disorder
c - 1/2
d - being a carrier
If a father has an X-linked recessive disorder, what will his son or daughter have?
Son will be healthy as they only inherit Y from father not X which trait is on.
Daughters will all be carriers as they will inherit the X from the father.
If a father has an X-linked dominant disorder, what will his son or daughter have?
All daughters but no sons will be affected. Conditions often milder and more variable in females.
How do we know Hypophosphatemia is a Dominant X linked disorder?
PHEX gene mutation
overproduction of FGF21 which inhibits kidney phosphate resorption. Results in VD resistance rickets
X linked because of overproduction characteristic. We cannot counter that with a normal gene
