Genetics

Question 1

variable expressivity

Answer 1

patients with the same genotype with varying phenotypes, e.g.: NF1

Question 2

incomplete penetrance

Answer 2

not all individuals with a mutant genotype show the mutant phenotype, e.g.: BRCA, osler weber rendu

Question 3

somatic mosaicism

Answer 3

presence of genetically distinct cell lines in same person. mutation happens from mitotic errors after fertilization and propagates though multiple tissues or organs

Question 4

gonadal mosaicism

Answer 4

mutations only in egg or sperm cells. if parents and relatives don’t have disease, suspect gonadal or gremlin mosaicism. e.g.: mccune albright syndrome

Question 5

locus heterogeneity

Answer 5

mutations at diff loci produce the same phenotype e.g.: albinism

Question 6

allelic heterogenity

Answer 6

diff mutations at the same locus produce same phenotype- e.g. beta thal

Question 7

heteroplasmy

Answer 7

presence of both normal and mutated mt dan-> variable expression in mitochondrially inherited disease

Question 8

uniparental disomy

Answer 8

offspring receives two copies of a chromosome from one parent. usually no disease. heterodisomy= meiosis I error. Idodisomy (homozygous) indicates a meiosis II error or a post zygotic chromosomal duplication of one of a pair