Lecture 1

Question 1

Direction of DNA replication and transcription

Answer 1

5’ ———> 3’

Double strands are antiparallel to each other

Question 2

DNA base pair related to melting temperature

Answer 2

GC

Melting temperature = temperature at which 1/2 of DNA strands are denatured

Question 3

Cytarabine

Answer 3

Cytosine arabinoside; useful in treatment of non-Hodgkin’s lymphoma and acute myelogenous leukemia

Question 4

Template strand

Answer 4

DNA strand to which newly forming RNA binds; also known as the anti-sense strand

Question 5

Sense strand

Answer 5

DNA strand that is “replaced” by new RNA molecule; also known as the non-template strand or “coding sequence”

Question 6

Modifications of mRNA (3)

Answer 6

1) Add m^7Gppp (7-methyl guanylate) to 5’ end, creating 5’->5’ linkage; and methylate some 2’ OH
2) Add poly-A tail to 3’ end
3) Splice to remove introns

Question 7

Aniridia

Answer 7

Lack of iris, caused by added exon in PAX6 mRNA

Question 8

Start codon

Answer 8

AUG

Question 9

Stop codon (in RNA and DNA)

Answer 9

UAA, UAG, UGA

TAA, TAG, TGA

Question 10

Degeneracy

Answer 10

Allowance for wobble in RNA codon’s 3rd nucleotide; caused by promiscuous inosine in 1st anticodon position

Question 11

RNA translation initiation (3 steps)

Answer 11

1) poly-A tail bound by poly-A binding protein, which attracts initiation factors
2) Small ribosomal subunit binds to 5’ end
3) Small subunit slides until AUG found, at which point large subunit attaches