Genetic Terms

Question 1

Codominance

Answer 1

Both alleles contribute to the phenotype of the heterozygote; Blood groups, antitrypsin deficiency

Question 2

Variable expressivity

Answer 2

Phenotype varies among individuals with same genotype

Question 3

Incomplete penetrance

Answer 3

Not all individuals with a mutant genotype show the mutant phenotype; BRCA 1 gene

Question 4

Pleiotropy

Answer 4

One gene contributes to multiple phenotypic effects; PKU

Question 5

Anticipation

Answer 5

Increased severity or earlier onset of disease in succeeding generations; Huntington’s Disease

Question 6

Mosaicism

Answer 6

Presence of genetically distinct cell lines in the same individual

Question 7

Somatic mosaicism

Answer 7

Mutation arises from mitotic errors after fertilization and propagates through multiple tissues and organs

Question 8

Gonadal mosaicism

Answer 8

Mutation only in egg or sperm cells

Question 9

Allelic heterogeneity

Answer 9

Different mutations in the same locus produces the same phenotype; B-thalassemia

Question 10

Locus heterogeneity

Answer 10

Mutations at different loci can produce a similar phenotype; Albinism