Genetics

Question 1

Edward’s syndrome:
trisomy #?
results of quad screen?

Answer 1

trisomy 18
down alpha-fetoprotein, beta-hCG, and estriol
normal inhibin A

Question 2

Patau’s syndrome
trisomy #?
typical signs?
results of quad screen?

Answer 2

trisomy 13
retardation, rocker-bottom feet, microphthalmia, microcephaly, cleft lip/palate, holoprosencephaly, polydactyly, heart disease.

Question 3

22q11 deletion presentation

syndromes

Answer 3

CATCH-22
Cleft palate
Abnormal facies
Thymic aplasia –> T-cell deficiency
Cardiac defects
Hypocalcemia –> due to parathyroid aplasia
DiGeorge Syndrome - thymic, parathyroid, cardiac defects
Velocardiofacial syndrome - palate facial, cardiac defects

Question 4

What are the 3 STOP codons (mRNA)?

Answer 4

UGA (U Go Away!)
UAG (U Are Going!)
UAA (U Are Away.)

Question 5

What tests are included in the triple screen for chromosomal abnormalities and neural tube defects?

Answer 5

AFP, β-HCG, and ESTRIOL

Question 6

What test is added to the triple screen to make the quad screen?

Answer 6

inhibin-A

Question 7

So what tests are included in the quad screen?

Answer 7

AFP, β-HCG, estriol, inhibin-A

Question 8

What are the 3 special properties of the genetic code?

Answer 8

Universal (except mitochondria)
Degenerate (multiple codons for 1 aa)
Unambiguious (each codon only codes 1 aa)

Question 9

What is the start codon in mRNA?

Answer 9

AUG (It inAUGurates translation.)

Question 10

What is always the first amino acid on a new polypeptide chain in eukaryotes? In prokaryotes?

Answer 10

Met; f-Met (formyl-Methionine)

Question 11

What is the mutation in sickle cell anemia (at the level of the polypeptide chain)?

Answer 11

Glu–>Val @position 6

Question 12

How are the properties of Glu and Val different?

Answer 12

Glu is acidic, hydrophilic, polar; Val is neutral, hydrophobic.

Question 13

Define a nonsense mutation.

Answer 13

Point mutation encodes STOP codon.

Question 14

What kind of mutation is α-thallasemia most commonly caused by? How does this occur?

Answer 14

Large segmental deletion - unequal crossover

Question 15

What kid of mutation are β-thallasemias usually caused by?

Answer 15

splice site mutation

Question 16

Name 2 disease, aside from Huntington’s and myotonic dystrophy that result from trinucleotide expansion repeats.

Answer 16

Friedrich’s ataxia

Fragile X syndrome

Question 17

What is the repeated triplet in Huntington’s and what aa does it code for?

Answer 17

CAG –> Gln

Question 18

What is the trinucleotide repeated in mytonic dystrophy type 1?

Answer 18

CTG