Term
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Definition
| The researchers began their work by growing viruses in the presence of either a radioactive isotope of sulfur (35S) or a radioactive isotope of phosphorus (32P). They allowed each set of radioactive viruses to infect E. coli cells. If genes consist of DNA, then radioactive DNA should be located inside the cells; but genes consist of protein, then radioactive proteins should be inside the cells. |
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Term
| Meselson-Stahl experiment |
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Definition
| Meselson and Stahl began by growing E. coli cells with nutrients that contained only 15N. They purified DNA from a sample of these cells and transferred the rest of the culture to a growth medium containing only the 14N isotope. After enough time had elapsed for these cells to divide once—meaning that the DNA had been copied once—they removed a sample and isolated the DNA. After the remainder of the culture had divided again, they removed another sample and isolated its DNA. The results would be different if in the first generation there was a DNA that was completely made of new strand and then if the F2 there was 3 daughter DNA to the one parent (conservative); or, if the F1 was a hybrid, and the F2 was dispersed throughout all DNA (dispersed). |
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Term
| dNTP (deoxynucleoside triphosphate) |
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Definition
| a nucleotide containing adenine, thymine, guanine, or cytosine with 3 phosphate groups and a 5' carbon sugar |
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Term
| How does DNA polymerase use a dNTP to synthesize a new strand of DNA |
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Definition
| A condensation reaction results in the formation of a phosphodiester bond between the 3’ carbon on the end of a DNA strand and the 5’ carbon on an incoming deoxyribonucleoside triphosphate (dNTP) monomer. |
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Term
| T/F: During DNA replication, the DNA TEMPLATE STRAND is always READ in the 5' to 3' direction |
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Definition
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Term
| T/F: the NEW STRAND of DNA is SYNTHESIZED ONLY in the 5' to 3' direction during replication |
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Definition
| False, its replicated in both directions at the same time |
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Term
| Eukaryotic chromosomes have _________ origins of replication; bacterial chromosomes have a ________ origin of replication |
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Definition
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Term
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Definition
| localized separation of two strands of DNA |
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Term
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Definition
| the Y-shaped site at which a double-stranded molecule of DNA is separated into two single strand for replication |
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Term
| The leading strand is ___________ while the lagging strand is _______________ |
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Definition
| continuous; discontinuous |
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Term
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Definition
| short segments of DNA produced during replication of the lagging strand template; many Okazaki fragments make up the lagging strand in newly synthesized DNA |
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Term
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Definition
| extends the leading strand |
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Term
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Definition
| extends an Okazaki fragment |
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Term
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Definition
| a short stretch of DNA that acts as a primer for DNA polymerase |
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Term
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Definition
| catalyzes the synthesis of the RNA primer |
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Term
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Definition
| catalyzes the breaking of hydrogen bonds (denaturation) between base pairs to open the double helix |
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Term
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Definition
| breaks and rejoins the DNA double helix to relieve twisting forces caused by the opening of the helix |
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Term
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Definition
| catalyzes the joining of Okazaki fragments into a continuous strand |
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Term
| Single-strand DNA-binding proteins (SSBPs) |
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Definition
| stabilizes single-stranded DNA (keeps two strands apart) |
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Term
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Definition
| holds DNA polymerase in place during strand extension |
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Term
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Definition
| each strand of DNA that is replicated contains one new strand of DNA and one old strand of DNA |
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Term
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Definition
| DNA replication occurs in both directions at the same time; thus replication bubbles grow in two directions as DNA replication proceeds |
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Term
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Definition
| one strand is continuous and the other is discontinuous during DNA replication |
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Term
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Definition
| the end portion of a chromosome that is unreplicated |
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Term
| Why are telomeres of the lagging strand not completely synthesized during DNA replication? |
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Definition
| DNA polymerase is unable to add DNA near the tip of the chromosome, because it cannot synthesize DNA without a primer. As a result, the single-stranded DNA that is left stays single stranded. |
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Term
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Definition
| an enzyme that adds DNA to the ends of chromosomes (telomeres) by catalyzing DNA synthesis from an RNA template that is part of the enzyme |
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Term
| How does telomerase assist in replication of DNA ends? |
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Definition
| By extending the number of repeated sequences in the 5’ 3’ direction, telomerase provides room for enzymes to add an RNA primer to the lagging-strand template. Normal DNA replication enzymes can then fill in the missing section of the lagging strand. |
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Term
| Cells that have telomerase activity |
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Definition
-stem cells
-cancer cells
-cells that produce gametes |
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Term
| T/F: Telomere shortening DOESN'T have a role in limiting the number of cell divisions for somatic cells |
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Definition
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Term
| What does it mean to say that strands in a double helix are antiparallel? |
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Definition
| They have opposite directionality, or polarity |
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Term
| The enzyme that removes twists in DNA ahead of the replication fork is...... |
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Definition
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Term
| What is the function of primase? |
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Definition
| synthesis of a short RNA, complementary to single-stranded DNA |
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Term
| How are Okazaki fragments synthesized? |
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Definition
| using the lagging strand template, and synthesizing 5' --> 3' |
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Term
| An enzyme that uses an internal RNA template to synthesize DNA is... |
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Definition
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Term
| Researchers design experiments so that only one thing is different between the treatments that are being compared. In the Hershey-Chase experiment, what was this single difference? |
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Definition
| Labeling DNA or labeling proteins |
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Term
| What is the relationship between defective DNA repair and cancer? |
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Definition
| DNA is constantly damaged, and many pathways have evolved to repair this onslaught of damage. If a DNA repair pathway is inactivated by mutation, damage is inefficiently repaired. Consequently mutation rates increase, and the increased number of mutations increases the probability that cancer-causing mutations will occur |
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Term
| Why is the synthesis of the lagging strand of DNA discontinuous? How is it possible for the synthesis of the leading strand to be continuous? |
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Definition
| On the lagging strand, DNA polymerase moves away from the replication fork. When helicase unwinds a new section of DNA, primase must build a new primer on the template for the lagging strand (closer to the fork) and another polymerase molecule must begin synthesis at this point. This makes the lagging-strand synthesis discontinuous. On the leading strand, DNA polymerase moves in the same direction as helicase, so synthesis can continue, without interruption, from a single primer (at the origin of replication) |
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Term
| Explain how telomerase prevents linear chromosomes from shortening during replication. |
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Definition
| Telomerase binds to the overhang at the end of a chromosome. Once bound, it begins catalyzing the addition of deoxyribonucleotides to the overhang in the 5' --> 3' direction, lengthening the overhang. This allows primase, DNA polymerase, and ligase to catalyze the addition of deoxyribonucleotides to the lagging strand in the 5' --> 3' direction, restoring the lagging strand to its original length |
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Term
| Predict what would occur in a bacterial mutant that lost the ability to chemically mark the template strand of DNA |
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Definition
| the mutation rate would increase (because the ability to distinguish which strand contains the incorrect base would be lost) |
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Term
| What aspect of DNA structure makes it possible for the enzymes of nucleotide excision repair to recognize many different types of DNA damage? |
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Definition
| The regularity of DNA's overall structure (it allows enzymes to recognize any type of damage that distorts this regular structure) |
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