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36 Cards in this Set
- Front
- Back
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Replication of DNA is catalyzed by _____ and requires ______
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-DNA polymerase
-template - ssDNA -substrates - dATP, dCTP, dGTP, dTTP |
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DNA undergoes ______, where one DNA is the parental strand, and the other is the new strand
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semiconservative replication
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In (prokaryotes/eukaryotes), replication begins at single, unique origin of replication
In (prokaryotes/eukaryotes), replication begins at multiple sites along genomic DNA |
-prokaryotes
-eukaryotes |
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Origin of replication is usually _____ rich. This makes sense because strands must be ____ at the start site
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-AT rich
-melted *AT bonds only form by 2 hydrogen bonds, making it easier to melt |
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When strands replicate, they form a V-like structure called a ____
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replication fork
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______ protein binds and melts dsDNA
______ unwinds double helix |
-DnaA protein
-DNA helicase |
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During replication, ssDNA-binding (SSB) proteins bind to ssDNA to:
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-keep strands separate
-protect from nucleases (nuclease breaks phosphodiester bonds between nucleotide sequences - ssDNA is more susceptible to nuclease) |
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Unwinding of DNA forms _____ ahead of the fork
The enzyme _____ removes these and facilitates transcription |
-supercoils
-DNA topoisomerases |
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DNA polymerase reads DNA in the _____ direction and synthesizes DNA in the ______ direction
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-3' - 5'
-5' - 3' |
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The _____ strand is copied continuously and the ____ strand is copied discontinously
In the lagging strand, small fragments of DNA, called ______, are copied near the replication fork |
-leading
-lagging -okazaki fragments |
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DNA polymerase require ____ to initiate synthesis, which is synthesized by _____
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-RNA primer
-primase (a specific RNA polymerase) |
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_____ uses RNA primer to initiate replication
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DNA polymerase III
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Elongation is catalyzed by _____
This enzyme stays bound to DNA all the way during synthesis and is responsible for proofreading during replication |
DNA polymerase III
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____ synthesizes the lagging strand until it is blocked by RNA primer and _____ locates the space between DNA and RNA and replaces the RNA primer with DNA
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-DNA pol III
-DNA pol I |
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DNA fragments of lagging strand are linked by _____ enzymes by forming _____ bonds between 3' ____ end and 5' ____ end
This requires _____ |
-DNA ligase
-phosphodiester bonds -3' hydroxyl -5' phosphate -ATP |
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DNA pol I reads parental DNA in what direction?
DNA pol II? DNA pol III? |
DNA pol I
-5' - 3' when filling gap after removal of RNA primer -3' - 5' when removing RNA primer DNA pol II -3' - 5' - DNA repair DNA pol III -3' - 5' - replication of DNA |
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DNA repair and recombinant DNA techniques use what enzyme?
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DNA ligase
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In eukaryotes, the RNA primer is removed by _____
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RNAse H
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Period preceding replication is ____
Replication occurs during _____ When a cell undergoes rapid growth and prepares for mitosis is ______ Mitosis is the _____ When a cell stops dividing, it is in the _____ |
-G1 phase
-S (synthesis) phase -G2 phase -M phase -G0 phase |
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What are all the different types of eukaryotic polymerases and what are their functions?
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Shortening of DNA is due to inability to fill gap at extreme (3'/5') end
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-5' end
*results in loss of genetic information and is associated with aging |
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The end of the chromosome contains highly repetitive DNA called _____
What is the repetitive unit for human (6 nucleotides long)? |
-telomere
-TTAGGG |
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What are all the functions of of telomeres?
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-Serve as a buffer, which is consumed during cell division
-Protect the ends from nucleases -Limit cells to a fixed number of divisions, in most somatic cells -Loss of DNA leads to cell senescence and death |
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Telomeres can be replenished by _____, which is active in germ, stem, and cancer cells
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telomerase
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Exercise has be found to increase _____ in aorta and mononuclear (immune) cells in mice
High levels of vitamin D is also associated with longer ____ |
-telomerase
-telomere |
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How does telomerase, a ribonucleoprotein, work?
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-it's a RNA-dependent DNA polymerase that contains RNA that is complementary to repetitive sequence in telomere
-it uses the 3' end of DNA as a primer and RNA as a template to extend 3-end of parental strand in DNA |
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DNA can be damaged by mutagens. What are some mutagens?
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-chemicals produced by cell
-chemical from environment -radiation |
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______ can cause transformation of cells into cancer cells
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-carcinogens
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X-rays that produce free radicals from H2O is and example of (direct/indirect) DNA damage
Cigarette smoking is an example of (direct/indirect) DNA damage |
-indirect
-direct |
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Cigarette smoke contains what carcinogen?
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-benzo[a]pyrene
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UV light forms covalent dimer between adjacent ______ on DNA strand
_____ is an autosomal recessive disease where there is a genetic defect in nucleotide excision repair (NER) system and cells can not repair DNA damage from UV light |
-thymines
-Xeroderma pigmentosum |
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Give an example of:
Direct repair Nucleotide excision repair Base excision repair |
-Direct - E.coli removes thymine dimer by phagoactivating enzymes
-Nucleotide - endonuclease cleaves abnormal chain and removes distorted region. Gap filled by DNA polymerase and joined by DNA ligase -Base - *DNA glycosylases* recognize distortion and cleaves N-glycoside bond. *AP endonuclease cleaves sugar-phosphate strand at this site |
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What are the four steps to repair DNA?
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Recognition
Removal Replacement Joining |
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How enzymes know which DNA to repair in bacteria and in humans?
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-Bacteria - adenine bases in parental strand is methylated and newly synthesized strand is repaired
-Humans - unknown |
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During reverse transcription, what happens to RNA after ssDNA is made?
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RNA is degraded
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Didanosine (ddI) is used for:
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-inhibition of reverse transcription
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