First Aid

Question 1

Examples for Codominance ?

Answer 1

ABO blood groups
HLA groups
Alpha1-antitrypsin deficiency

Question 2

Loss of heterogeneity ? Example ?

Answer 2

If a patient inherits or develops a mutation in a tumor suppressor gene , the complementary allele must be deleted or mutated before cancer develops 
Examples : 
Retinoblastoma ( two-hits hypothesis )
Lynch syndrome 
Li-Fraumeni syndrome

Question 3

Dominant negative mutation ? Example ?

Answer 3

Exerts a dominant effect , a heterozygote produces a non functional altered protein that also prevents the normal gene product from functioning
Example : mutation of a transcription factor in its allosteric site , the non functioning mutant can still binds DNA preventing wild-type transcriptional factor from binding

Question 4

McCune Albright syndrome ? Mechanism and effect

Answer 4

Due to mutation affecting G-protein signaling
Presents with :
Unilateral café-au-lait spots with ragged edges
Polyostotic fibrous dysplasia
At least one endocrinooathy ( precocious puberty )
Lethal if mutation occurred before fertilization
Survivable in patients with mosaicism

Question 5

Uniparental disomy ? Def and Types ?

Answer 5

Offspring receives 2 copies of a chromosome from 1 parent and no copies from other parent
Types :
Heterodisomy :indicated a meiosis l error
Isodisomy : idicated a meiosis ll error or postzygotic chromosomal duplication of one of a pair of chromosomes and loss of the original pair

Question 6

Leper hereditary optic neuropathy ?

Answer 6

Mitochondrial inherited disease
Cell death in optic nerve neurons leads to subacute bilateral vision loss in young adults
90% males
Usually permanent