Genetics

Question 1

Mutation

Answer 1

Permanent change in the DNA sequence

Question 2

Mutagen

Answer 2

Substance that causes a mutation, such as radiation, food additives, cigarette smoke, etc.

Question 3

Mutant

Answer 3

An allele that differs from the wild type, which alters the phenotype

Question 4

Spontaneous mutation

Answer 4

Genetic change results from the mispairing of bases during replications

Question 5

Missence mutation

Answer 5

Change in a codon so that it codes for a different emino acid

Question 6

Locus: USH1

Answer 6

11q13.5

Question 7

Locus: USH2

Answer 7

10q21-q22

Question 8

Locus: USH3

Answer 8

1q41

Question 9

Mapped genes for USH1

Answer 9

MYO7A

Question 10

Mapped genes for USH2

Answer 10

Harmonin (CDH23)

Question 11

Mapped genes for USH3

Answer 11

USH2A

Question 12

Function of protein for USH1

Answer 12

Unconventional myosin is involved in the organization of transmembrane proteins

Question 13

Function of protein for USH2

Answer 13

Harmonin is a cadherin-like protein that resembles extracellular matrix protins or cell adhesion molecules

Question 14

Function of protein for USH3

Answer 14

Unknown

Question 15

Loci for Pendred syndrome

Answer 15

7q22-31.1

Question 16

Mapped genes for Pendred

Answer 16

PDS

Question 17

Function of protein for Pendred

Answer 17

• Pendrin, a transmembrane protein, is expressed in the thyroid and inner ear
• In the cochlea, pendrin is expressed in regions of endolymp resorption

Question 18

Loci for DFNA 6/14/38

Answer 18

4p16.3

Question 19

Mapped genes for DFNA 6/14/38

Answer 19

• Heterozygous missense mutation of the WFSI gene

- Expression of this gene is localized to certain neurons including the ventral cochlear nucleus and inferior colliculus

Question 20

Function of protein for DFNA 6/14/38

Answer 20

• Function of WFSI is unknown, but is expressed in the tissue of the brain and pancreas
• It is thought to play a role in membrane trafficking, protein processing, and regulation of calcium homeostasis

Question 21

Loci for GJB2 mutation

Answer 21

13q11q12

Question 22

Mapped genes for GJB2 mutation

Answer 22

Mutations in Connexin 26 are the most common cause of recessive non-syndromic deafness

Question 23

Function of protein for GJB2

Answer 23

• Connexin genes code for subunits of gap junction proteins
• Gap junction proteins form intercellular channels in plasma membrane for transport of fluid and small molecules
• The gap junctions are essential to recycling potassium ions required to initiate action potentials in hair cells

Question 24

Prevalence of Usher Syndrome

Answer 24

As high in 6,000

Question 25

Prevalence of Pendred Syndrome

Answer 25

7-8% of all congenital hearing losses

Question 26

Prevalence DFNA 6/14/38

Answer 26

0.28-1% of all congenital hearing losses

Question 27

Prevalence of DFNB1

Answer 27

50% of all congenital hearing loss cases in the US

14 of 100,000