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22 Cards in this Set
- Front
- Back
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DNA replication
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semiconservative (half parent in each daughter)
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DNA replication steps
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1. helix unwound by helicase (break hbonds)
2. DNA polymerase: complimentary strands 5' to 3' replication fork formed leading strand continuously with one RNA primer lagging strand discontinuously with RNA primer for every Okazaki fragment |
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DNA transcription
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information stored in the bases of DNA is copied into RNA
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Transcription steps
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1. RNA polymerase bind to TATA box of template strand
2. nucleotides added 5' to 3' 3. heterogeneous nuclear RNA formed intron cleaved, exons together: mRNA 5' capped 3' poly A tail mRNA leaves nucleus through nuclear pores |
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Translation
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synthesis of amino acid chain using mRNA as a template
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Translation steps
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in cytoplasm requires energy GTP
1. mRNA binds to ribosome (starts at start codon) 2. tRNA delivers amino acids to the ribosome 3. the tRNA/amino acid complex temporarily bind the mRNA codon 4. protein synthesis stops at stop codon 5. post-translational modifications (3-d folding) |
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small scale mutations
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base substitutions
deletions insertions |
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base substitutions
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transition
transversion |
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transition
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pyrimidine (CT) for pyrimidine
purine for purine |
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transversion
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pyrimidine for purine
or purine for pyrimidine |
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deletions
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nucleotides lost from sequence
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insertions
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nucleotides added to a sequence
includes transpositions |
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transposition
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sequence inserted at an incorrect location in the DNA
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causes for DNA damage
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mismatches during DNA replication
spontaneous deamination alkylation of bases UV light causing formation of thymine dimers ionizing radiation producing double strand breaks chemicals causing formation of bulky adducts |
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deamination
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cytosine loses its amino group to form uracil
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alkylation
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addition of methyl group to bases
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DNA repair mechanisms
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direct repair
base excision repair mismatch repairs nucleotide excision repair post-replication repair |
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direct repair
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reverse DNA damage without cutting deoxyribose phosphate backbone
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base excision repair
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when incorrect bases are present in DNA.
glycosylase recognize damage hydrolytically removed from backbone leaves apurinic or apyrimidic site correct base inserted break sealed by DNA ligase |
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mismatch repairs
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similar to BER
for incorrect pairings of normal bases |
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nucleotide excision repair
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removes thymine dimers and bulky adducts
unwind area endonuclease makes cuts on 5' and 3' sides exonuclease removes base DNA resynthesized using sister strand DNA ligase seals |
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post-replication repiar
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repair double stranded breaks
recombinational repiar use single strand from homologous chromosome broken ends rejoined directly and ligated original not always maintained mutations (translocations) often |
