05-17-2011, 01:42 PM
Explanations:
1.C
Anticipation is a special form of variable expressivity in which the age of onset of a disorder decreases and/or the severity of the phenotype increases in successive generations. In the case of myotonic dystrophy (an autosomal dominant disorder), this is caused by expansion of a (CTG) repeat within the gene in each generation.
2.E
Deafness is characterized by locus heterogeneity in which mutations in distinct genes can result in the identical clinical phenotype. Because the genetic pathway controlling hearing is complex and is dependent on multiple gene interactions, it is likely that the two parents have mutations is different genes. As a consequence, their progeny can inherit a functional copy of each required gene in the hearing pathway from the combination of functional genes from each of the two parents.
3.D
In variable expressivity, different affected family members display different features of the inherited condition (i.e. variations in the nature and severity of the phenotype). This modulation in expression is attributed to the influence of other genes and environmental factors.
4.B
In allelic heterogeneity multiple mutations within a single gene(locus)/gene product can produce the disease.(same or similar phenotype)
1.C
Anticipation is a special form of variable expressivity in which the age of onset of a disorder decreases and/or the severity of the phenotype increases in successive generations. In the case of myotonic dystrophy (an autosomal dominant disorder), this is caused by expansion of a (CTG) repeat within the gene in each generation.
2.E
Deafness is characterized by locus heterogeneity in which mutations in distinct genes can result in the identical clinical phenotype. Because the genetic pathway controlling hearing is complex and is dependent on multiple gene interactions, it is likely that the two parents have mutations is different genes. As a consequence, their progeny can inherit a functional copy of each required gene in the hearing pathway from the combination of functional genes from each of the two parents.
3.D
In variable expressivity, different affected family members display different features of the inherited condition (i.e. variations in the nature and severity of the phenotype). This modulation in expression is attributed to the influence of other genes and environmental factors.
4.B
In allelic heterogeneity multiple mutations within a single gene(locus)/gene product can produce the disease.(same or similar phenotype)