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In this chapter, we focused on how DNA is replicated and synthesized. In particular, we elucidated the general mechanism of replication and described how DNA is synthesized when it is copied. Based on your study of these topics, answer the following fundamental questions:
(a) What is the experimental basis for concluding that DNA replicates semiconservatively in both prokaryotes and eukaryotes?
(b) How was it demonstrated that DNA synthesis occurs under the direction of DNA polymerase III and not polymerase I?
(c) How do we know that in vivo DNA synthesis occurs in the 5' to 3' direction?
(d) How do we know that DNA synthesis is discontinuous on one of the two template strands?
(e) What observations reveal that a "telomere problem" exists during eukaryotic
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Essentials of Genetics (9th Edition) - Standalone book
- During high stress environments, it has been found that some bacteria activate a genetic mechanism that allows them to incorporate more mutations into the DNA during replication. Would the following two enzymes be impacted by such a mechanism? (i)DNA polymerase IIIii) Helicasearrow_forwardSuppose that replication is initiated in a medium containing moderately radioactive tritiated thymine. After a few minutes of incubation, the bacteria are transferred to a medium containing highly radioactive tritiated thymidine. Sketch the autoradiographic pattern that would be seen for (a) undirectional replication and (b) bidirectional replication, each from a single origin.arrow_forwardThere are 6 parts to this question: This is a follow up to the prior question regarding the replication of the DNA strand below. The DNA strand is here for your reference and you do not need to do anything with or to it. TC GATATCGG AGCTATAGCC c) what enzyme separated the parental DNA template strands, d) what bonds were broken? e) what enzyme replicates DNA f) before DNA can be replicated/copied, what must be laid down to allow the enzyme in "e" to replicated the DNA (be specific)? g) our DNA is replicated in many "pieces", what enzyme connects these many "pieces" into one continuous DNA strand that becomes the sister chromatid? h) during what specific phase of the cell cycle does this DNA replication process occur? (This should be a review question from last topics we covered).arrow_forward
- Why is the replication of DNA referred to as a semiconservative process? What is the experimental evidence for the semiconservative nature of the process? What experimental results would you expect if replication of DNA were a conservative process?arrow_forwardWhich of the following is NOT correct concerning the initiation of replication in E. coli? Question 29 options: A) It involves a region of the DNA called oriC. B) DnaA proteins bind to the DNA to begin separation of the strands. C) The strands are initially separated at GC-rich regions of DNA. D) Following initial separation, enzymes continue to separate the parental DNA strands around the rest of the chromosome.arrow_forward(a) Eukaryotic DNA replication is more complex than prokaryotic replication. Give one reason why this should be so. (b) Why might eukaryotic cells need more kinds of DNA polymerases than bacteria?arrow_forward
- Which of the followings statements are true about DNA polymerase? 1.) It can only go in one direction, meaning the lagging strand can't be synthesized continuously. 2.) It cannot start a DNA strand from scratch, so another enzyme is needed to create "primers" as a starting point. 3.) It cannot copy epigenetic marks (such as methyl groups) on its own; these must be "copied" onto the daughter DNA strand by other enzymes after DNA replication. 4.) All of the abovearrow_forwardThe E. coli chromosome is 1.28 mm long. Under optimal conditions, thechromosome is replicated in 40 minutes.(a) What is the distance traversed by one replication fork in 1 minute?(b) If replicating DNA is in the B form (10.4 base pairs per turn), how manynucleotides are incorporated in 1 minute in one replication fork?(c) If cultured human cells (such as HeLa cells) replicate 1.2 m of DNAduring a five-hour S phase and at a rate of fork movement one-tenthof that seen in E. coli, how many origins of replication must the cellscontain?(d) What is the average distance, in kilobase pairs, between these origins?arrow_forwardWhy is DNA replication is considered a semi-discontinuous process? Explain in detail.arrow_forward
- Spontaneous deamination of cytosine bases in DNA takes place at low but measurable frequency. Cytosine is converted into uracil by loss of its amino group. After this conversion, which base pair occupies this position in each of the daughter strands resulting from one round of replication? Two rounds of replication? (a) How many different 8-mer sequences of DNA are there? (Hint: There are 16 possible dinucleotides and 64 possible trinucleotides.) We can quantify the information- carrying capacity of nucleic acids in the following way. Each position can be one of four bases, corresponding to two bits of information (2² = 4). Thus, a chain of 5100 nucleotides corresponds to 2 × 5100 = 10,200 bits, or 1275 bytes (1 byte =8 bits). (b) How many bits of information are stored in an 8-mer DNA sequence? In the E. coli genome? In the human genome? (c) Compare each of these values with the amount of information that can be stored on a computer compact disc, or CD (about 700 megabytes).arrow_forwardAnswer the following questions with regards to DNA replication:1. In what direction does DNA polymerase read the parent strand?2. Describe why Okazaki fragments are formed (1-2 sentences)3. In no more than one sentence describe the function of the following enzymes as it pertains to DNA replication in E. coli : DNA polymerase III, primase and ligasearrow_forwardDNA replication is semi-conservative, this statement means that Question 6 options: a) the new DNA molecules that are made are not identical to the original DNA molecule. b) the new DNA molecules that are made are only partially DNA since RNA primers are included. c) the new DNA molecules that are made are composed of one strand of the old DNA molecule and one strand of new DNA. d) of the two new DNA molecules made, one is entirely new DNA and one is entirely old new. e) the new DNA molecules that are made have a mixture of old and new DNA in each strand of the DNA duplex, randomly interspersed.arrow_forward
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