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29 Cards in this Set
- Front
- Back
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Which drugs act on reverse transcriptase to combat retroviruses, such as HIV?
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AZT, ddC, and ddI
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What are the four main types of damage to DNA and what is the cause of each?
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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 |
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What enzyme recognizes the thymine dimer mutations in a strand and what does it do?
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Excision endonuclease recognizes the mutation and simple cut the thymine dimer out of the mutated strand.
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What are the steps involved in repair after the excision endonuclease has excised the thymine dimer?
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DNA polymerase adds the correct DNA
DNA ligase follows and connect the bases |
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What disease is caused by a genetic deficiency of Excision endonuclease?
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Xeroderma Pigmentosum (XP)
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What does an uncorrected thymine dimer resemble?
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replication bubble
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What wil be the product of a cytosine deamination?
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uricil in the place of cytosine
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What enzyme recognizes the deaminated cytosine (uracil) and removes it?
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Uracil Glycosylase
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What happens when the Uracil is removed by Uracil Glycosylase?
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This leaves AP site (apurinic or apyrimidinate site)
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What can spontaniously cause the formation of an apurinic or apyrimidinic site?
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heat
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What enzyme recognizes the AP site and what does it do?
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AP endonuclease recognizes the AP site and removes the sugar and phosphate which remains there.
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What happens after the AP endonuclease has removed the damaged segment?
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As usual, it is followed by DNA polymerase and DNA logase
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What are the recognition enzymes which notice DNA replication mismatches?
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hMSH and hMLH proteins
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Why are the hMSH2 and hMLH1 genes clinically important?
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There can be mutations in these genes which will lead to loss of the MSH and MLH proteins which proofread replicated DNA
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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 |
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During which phase does the repair for each of the types of DNA damage take place?
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Thymine dimer - G1
cytosine deamination - G1 Apurination or Apyrimidination - G1 Mismatched base - G2 |
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What does the p53 gene's protein do?
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it prevents a cell with damaged DNA from entering the S phase.
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What syndrome does an inactivation of the p53 gene lead to?
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Li Fraumeni syndrome and many solid tumors.
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Why is the ATM gene important and in what diesase is a mutation in this gene seen in?
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ATM gene encodes a kinase essential for p53 activity.
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What does a mutation is the BrCa-1 gene lead to?
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BRCA-1 = breast, prostate and ovarian cancer
BRCA-2 = breast cancer |
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What is the most abundant type of RNA in a cell?
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rRNA
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What is the second most abundant type of RNA in the cell?
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tRNA
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What is another name for heterogeneous nuclear RNA?
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hnRNA or pre-mRNA
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What types of cells is hnRNA found in?
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only eukaryotic cells
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Where is snRNA found and what is it's function?
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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
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What are rybozymes and where are they foudn?
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ribozymes are RNA molecules with enzymatic activity and they are found in both prokaryotes and eukaryotes.
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What is the number designation given to the actual base at the start site of transciption?
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+1
everything upstream is given a negative number while everything downstream is given a positive number |
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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 |
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What is the direction of protein translation?
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from the amino terminus to the carboxy terminus
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