MEDT 491 exam 2 || with 100% Errorless Solutions.

Most of the inherited changes in our DNA arise because of unavoidable endogenous errors in cellular mechanisms and harmful effects of certain natural molecules and atoms within our cells correct answers True Most of the inherited changes in our DNA arise because of exposure to extracellular mutagens, including radiation sources and chemical mutagens. correct answers False Errors in DNA replication and DNA repair are a major source of mutations in our cells. correct answers True Significant chemical damage is sustained by DNA because of its proximity to water molecules in our cells. correct answers True Base cross-linking means that covalent bonds form between two bases. correct answers True The anti-cancer agent cisplatin causes a type of cross-linking between two guanine residues. correct answers True Pyrimidine dimers are a type of base cross-linking that is commonly induced by excess exposure to sunlight. correct answers True Cross-linked bases are on opposing DNA strands correct answers False Crosslinking of bases on opposing DNA strands is especially problematic for cells because it presents an obstacle to DNA replication (the replication fork stalls). correct answers True Crosslinking of bases on opposing DNA strands can be problematic for cells because it may present an obstacle to transcription (the RNA polymerase stalls). correct answers True Double strand DNA breaks are a challenge for cells because if repair is not affected immediately the ends can drift apart quickly making correct repair impossible correct answers True Repair of double stranded DNA breaks is easier in cells prior to DNA replication than after DNA replication has occurred correct answers False S-adenosylmethionine donates methyl groups to a range of different molecules in cells and frequently inappropriately methylates bases in DNA. correct answers True Guanine is occasionally methylated to give O-6-methylguanine which base pairs with adenine rather than with cytidine. correct answers False In each nucleated cell, about 300-600 adenines are converted to 3-methyladenine per day. correct answers True