Genetic Diseases

Question 1

Missense mutation

Answer 1

Single nucleotide substitution that can change the triplet base code and yield a different amino acid.

Can be conservative or non-conservative

Question 2

Nonsense mutation

Answer 2

Single nucleotide substitution producing inappropriate stop codon

Question 3

Frameshift mutation

Answer 3

Alteration of reading frame of DNA
If in multiple of 3 nucleotides - insertion or deletion of amino acid
If in other number - can lead to defective protein products (missense or nonsense)

Question 4

Trinucleotide repeat mutation

Answer 4

Amplification of triple nucleotide sequences leading to abnormal gene expression

Question 5

Pleiotropism

Answer 5

Multiple possible end effects of a single mutant gene

Question 6

Variable expressivity

Answer 6

Effect caused by a specific mutation

Question 7

Penetrance

Answer 7

Percentage if individuals who carry a gene and express the trait

Question 8

Genetic heterogeneity

Answer 8

Multiple different mutations leading to the same outcome

Question 9

Autosomal dominant disorders

Answer 9

Manifest in heterozygous state
Disease usually present in a parent
Clinical features modified by penetrance and expressivity
Clinical onset later than recessive
Most are loss if function

Question 10

Autosomal recessive disorders

Answer 10

Both alleles on a locus are mutated
Includes most inborn errors of metabolism
Expression of disease tends to be more uniform
onset early in life
De novo mutations not typically detected for several generations
Enzymes rather than structural proteins commonly affected

Question 11

X linked Disorders

Answer 11

Fully expressed in males
Most are recessive
Females pass mutation on to 50% of sons and 50% of daughters
Males pass mutation on to all daughters and no sons