Molecular Genetics Flashcards
Base Excision Repair (BER)
- happens when base is incorrectly placed and point mutations occur
- repaired by different glycosylases
glycosylase
- many different types
- keep phosphate backbone intact and only edit DNA base
example of failed BER
MUTYH polyposis conferring increased risk for colorectal cancer
point mutations in genetic conditions
1/3 related to deamination and corresponding damage
example of failed double stranded break repair
ATM mutations in Ataxia Teleangectasia
oligo-hybridization
two base pairs bind, third will not, but allows for proper ligation
topoisomerase inhibitors
can be good cancer drugs because they target frequent replication
Purines
Adenosine & Guanine
“Angels are pure”
Pyrimidines
Cytosine, thymine, uracil
5’-3’ direction
Implicated by polarity of DNA and RNA
Hydroxyl group
More reactive than hydrogen alone-makes RNA more susceptible to splicing
Nucleases
Digest linker RNA to release histone octamer
mitotic DNA packing
even tighter and requires gene expression to be turned off
s phase
part of cell cycle when DNA is replicated; only entered if cell is determined to be destined for division at the end of G1
interphase DNA
structured as chromatin
G0
phase cells enter if they are not destined to proliferate, but remain metabolically active
prophase
condensation of chromatin into chromosomes occurs and cell membranes break down, also have division and migration of centrioles
metaphase
DNA aligns itself along plate in center of cell in preparation for division
anaphase
centromeres split and begin to be pulled to opposite poles
telophase
nuclear membrane reforms and DNA begins decondensing into interphase form so that cytokinesis may begin
G1 checkpoint
monitors size of cell & DNA integrity; can cause cell cycle to arrest in order to continue growth
G2 checkpoint
looks at DNA synthesis and assesses for damage; can cause arrest of cell cycle to allow for further synthesis or repairs
M checkpoint
monitors spindle apparatus formation and kinetochore attachment to ensure appropriate division
cyclins
synthesized and destroyed with every round of cell cycle and division
Cdks
- not recycled, but only operate when complexed with cyclins
- regulate other processes and cell cycle proteins through phosphorylation
cyclinB+Cdk1 complex
phosphorylates to lead to membrane breakdown, reorganization of cellular cytoskeleton, aids in condensation
Rb
-mutations in this gene associated with many cancers
+one mutation increases risk to develop cancer (AD)
-acts at G1-S checkpoint
Proline
Every third helical turn in collagen due to its polarity
nonsense mediated decay
- 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)
co-translational transport pathway
translation begins and a signal sequence is translated, directing the ribosome to go to the ER
Branch point
A upstream of 3’ polypyrimidine tract involved in ensuring proper splicing
Exon junction complex
Marker of splice completion, can be multiple in a mature RNA
mutually exclusive exon
incorporation of one exon may automatically exclude the use of another in a transcript
internal splice site
included in some transcripts and not in others
substitution editing of RNA
-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
