Molecular Genetics

Question 1

Base Excision Repair (BER)

Answer 1

• happens when base is incorrectly placed and point mutations occur
• repaired by different glycosylases

Question 2

glycosylase

Answer 2

• many different types

- keep phosphate backbone intact and only edit DNA base

Question 3

example of failed BER

Answer 3

MUTYH polyposis conferring increased risk for colorectal cancer

Question 4

point mutations in genetic conditions

Answer 4

1/3 related to deamination and corresponding damage

Question 5

example of failed double stranded break repair

Answer 5

ATM mutations in Ataxia Teleangectasia

Question 6

oligo-hybridization

Answer 6

two base pairs bind, third will not, but allows for proper ligation

Question 7

topoisomerase inhibitors

Answer 7

can be good cancer drugs because they target frequent replication

Question 8

Purines

Answer 8

Adenosine & Guanine

“Angels are pure”

Question 9

Pyrimidines

Answer 9

Cytosine, thymine, uracil

Question 10

5’-3’ direction

Answer 10

Implicated by polarity of DNA and RNA

Question 11

Hydroxyl group

Answer 11

More reactive than hydrogen alone-makes RNA more susceptible to splicing

Question 12

Nucleases

Answer 12

Digest linker RNA to release histone octamer

Question 13

mitotic DNA packing

Answer 13

even tighter and requires gene expression to be turned off

Question 14

s phase

Answer 14

part of cell cycle when DNA is replicated; only entered if cell is determined to be destined for division at the end of G1

Question 15

interphase DNA

Answer 15

structured as chromatin

Question 16

G0

Answer 16

phase cells enter if they are not destined to proliferate, but remain metabolically active

Question 17

prophase

Answer 17

condensation of chromatin into chromosomes occurs and cell membranes break down, also have division and migration of centrioles

Question 18

metaphase

Answer 18

DNA aligns itself along plate in center of cell in preparation for division

Question 19

anaphase

Answer 19

centromeres split and begin to be pulled to opposite poles

Question 20

telophase

Answer 20

nuclear membrane reforms and DNA begins decondensing into interphase form so that cytokinesis may begin

Question 21

G1 checkpoint

Answer 21

monitors size of cell & DNA integrity; can cause cell cycle to arrest in order to continue growth

Question 22

G2 checkpoint

Answer 22

looks at DNA synthesis and assesses for damage; can cause arrest of cell cycle to allow for further synthesis or repairs

Question 23

M checkpoint

Answer 23

monitors spindle apparatus formation and kinetochore attachment to ensure appropriate division

Question 24

cyclins

Answer 24

synthesized and destroyed with every round of cell cycle and division

Question 25

Cdks

Answer 25

• not recycled, but only operate when complexed with cyclins

- regulate other processes and cell cycle proteins through phosphorylation

Question 26

cyclinB+Cdk1 complex

Answer 26

phosphorylates to lead to membrane breakdown, reorganization of cellular cytoskeleton, aids in condensation

Question 27

Rb

Answer 27

-mutations in this gene associated with many cancers
+one mutation increases risk to develop cancer (AD)
-acts at G1-S checkpoint

Question 28

Proline

Answer 28

Every third helical turn in collagen due to its polarity

Question 29

nonsense mediated decay

Answer 29

• ribosome displaces all exon junction complexes from mRNA during translation
• proteins associated with complexes to trigger cleavage of the 5’ cap and RNA degradation
• goal is to produce very little amounts of truncated protein
• does not occur if a premature stop codon is within 50 nt of the last splice junction (so often not at all in last exon)

Question 30

co-translational transport pathway

Answer 30

translation begins and a signal sequence is translated, directing the ribosome to go to the ER

Question 31

Branch point

Answer 31

A upstream of 3’ polypyrimidine tract involved in ensuring proper splicing

Question 32

Exon junction complex

Answer 32

Marker of splice completion, can be multiple in a mature RNA

Question 33

mutually exclusive exon

Answer 33

incorporation of one exon may automatically exclude the use of another in a transcript

Question 34

internal splice site

Answer 34

included in some transcripts and not in others

Question 35

substitution editing of RNA

Answer 35

-post transcriptional change to RNA to ultimately give different proteins
+ex: apolipoprotein B in gut v liver (T to U change)
+ex: deamination by ADARs and calcium permeability