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29 Cards in this Set

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Which drugs act on reverse transcriptase to combat retroviruses, such as HIV?
AZT, ddC, and ddI
What are the four main types of damage to DNA and what is the cause of each?
Thymine dimers due to UV radiation
Cytosine deamination due to chemicals or spontanious
Apurination or apyrimidination due to heat or spontanious
Mismatched base DNA replication errors
What enzyme recognizes the thymine dimer mutations in a strand and what does it do?
Excision endonuclease recognizes the mutation and simple cut the thymine dimer out of the mutated strand.
What are the steps involved in repair after the excision endonuclease has excised the thymine dimer?
DNA polymerase adds the correct DNA
DNA ligase follows and connect the bases
What disease is caused by a genetic deficiency of Excision endonuclease?
Xeroderma Pigmentosum (XP)
What does an uncorrected thymine dimer resemble?
replication bubble
What wil be the product of a cytosine deamination?
uricil in the place of cytosine
What enzyme recognizes the deaminated cytosine (uracil) and removes it?
Uracil Glycosylase
What happens when the Uracil is removed by Uracil Glycosylase?
This leaves AP site (apurinic or apyrimidinate site)
What can spontaniously cause the formation of an apurinic or apyrimidinic site?
heat
What enzyme recognizes the AP site and what does it do?
AP endonuclease recognizes the AP site and removes the sugar and phosphate which remains there.
What happens after the AP endonuclease has removed the damaged segment?
As usual, it is followed by DNA polymerase and DNA logase
What are the recognition enzymes which notice DNA replication mismatches?
hMSH and hMLH proteins
Why are the hMSH2 and hMLH1 genes clinically important?
There can be mutations in these genes which will lead to loss of the MSH and MLH proteins which proofread replicated DNA
What is a disease caused by mutations in hMSH2 or hMLH1 genes?
What does this many times get confused with?
hereditary nonpolyposis colorectral cancer

Do not confuse it with Familial polyposis of the colon
During which phase does the repair for each of the types of DNA damage take place?
Thymine dimer - G1
cytosine deamination - G1
Apurination or Apyrimidination - G1
Mismatched base - G2
What does the p53 gene's protein do?
it prevents a cell with damaged DNA from entering the S phase.
What syndrome does an inactivation of the p53 gene lead to?
Li Fraumeni syndrome and many solid tumors.
Why is the ATM gene important and in what diesase is a mutation in this gene seen in?
ATM gene encodes a kinase essential for p53 activity.
What does a mutation is the BrCa-1 gene lead to?
BRCA-1 = breast, prostate and ovarian cancer

BRCA-2 = breast cancer
What is the most abundant type of RNA in a cell?
rRNA
What is the second most abundant type of RNA in the cell?
tRNA
What is another name for heterogeneous nuclear RNA?
hnRNA or pre-mRNA
What types of cells is hnRNA found in?
only eukaryotic cells
Where is snRNA found and what is it's function?
small nuclear RNA is only found in the nucleus of eukaryotic cells and it's function is to participate in splicing (removal of introns) of mRNA
What are rybozymes and where are they foudn?
ribozymes are RNA molecules with enzymatic activity and they are found in both prokaryotes and eukaryotes.
What is the number designation given to the actual base at the start site of transciption?
+1
everything upstream is given a negative number while everything downstream is given a positive number
What is the mRNA codon associated with Methionine?
What end of the protein does this represent
AUG = methionine
Methionine is associated with the AMINO terminus of the protein
What is the direction of protein translation?
from the amino terminus to the carboxy terminus