Lecture 2 - Molecular and Mendelian Basis of Disease

Question 1

Probability that a mutant allele causes ANY phenotypic effect

Answer 1

Penetrance

Question 2

Variation in the degree/severity of the disease between individuals with a similar genotype

Answer 2

Variable expressivity

Question 3

a single gene has multiple phenotypic effects

Answer 3

pleiotropy

Question 4

circular genomic reference sequence

Answer 4

“o.” nomenclature

Question 5

Two types of loss of function mutations

Answer 5

null, hypomorphic

Question 6

Null vs. hypomorphic mutation

Answer 6

Null is complete LOF
Hypomorphic is partial LOF

Question 7

mutant allele interferes with function of the remaining wild-type allele causing >50% LOF

Answer 7

dominant negative mutation

Question 8

CNV vs. indel

Answer 8

CNV is > 1kb in size
Indel is 2bp-1kb in sizeS

Question 9

SNV vs. SNP

Answer 9

SNPs are limited to germline DNA and must be present in at least 1% of the population

Question 10

Variants in multiple different genes can cause a similar phenotype

1 phenotype, multiple genes

Answer 10

Locus heterogeneity

Question 11

Different variants in the same gene can cause different phenotypes

1 gene, multiple phenotypes

Answer 11

allelic heterogeneity

Question 12

heterozygotes express an intermediate, blended phenotype

Answer 12

incomplete dominance

Question 13

Two alleles affect the phenotype equally and separately (ex. blood types)

Answer 13

co-dominance

Question 14

ex., when allele frequency is high, AR condition may have AD pattern due to high carrier frequency

Answer 14

pseudodominance

Question 15

Fragile X repeats and full mutation size

Answer 15

CGG, >200 repeats

Question 16

Huntington’s disease repeats and full mutation size

Answer 16

CAG, >36 repeats

Question 17

Friedreich ataxia repeats and full mutation size

Answer 17

GAA, >70 repeats

Question 18

Myotonic dystrophy repeats and full mutation size

Answer 18

CTG, >100 repeats