Question

16.128 QUESTION 7 Please choose the answer which best fits the statement below. Not all answers will be used. This enzyme joins Okazaki fragments. A. Single strand binding protein These proteins help stabilize the two strands of B. DNA helicase the DNA at the replication bubble- they help C. Topoisomerase keep the strands from readhering to one D. DNA ligase another This enzyme adds new DNA nucleotides during E. DNA polymerase DNA replication This enzyme catalyzes the unwinding of the DNA at the replication fork. This enzyme, which works ahead of the replication fork, helps release tension created by the unwinding of the DNA. 6.46 QUESTION 8 The two strands of DNA in the double helix are anti-parallel. Explain what this means and what implications this has on the way DNA is replicated (be sure to mention how the DNA polymerase works and what this has to do with the lagging and leading strands) TTTT Paragraph Arial 3 (12pt) E. T %D09 T' T. fx Mashup 66 HTML CSS

Answer 1

I. The enzyme joins Okazaki fragments: DNA ligase

II. These proteins help in stabilize the two strands of DNA at replication bubble-they help , keep the strands from readhering to one another : Single strand binding protein

III. This enzyme adds new nucleotides during DNA replication : DNA polymerase

IV. This enzyme catalyzes the unwinding of the DNA at replication fork : DNA helicase

V. This enzyme, which works ahead of the replication fork, helps release tension created by the unwinding of the DNA : Topoisomerase

2) DNA is double stranded, and the strands are antiparallel because they run in opposite directions that one strand run from 5’ to 3’ and other is opposite to it from 3’ to 5’. Importance of an antiparallel DNA double helix structure is because of its hydrogen bonding between the complementary nitrogenous base pairs. If the DNA structure were to be parallel, the hydrogen bonding would not be possible. So the base pair formation did not possible. This structure allows for the DNA to be tightly packed into chromosomes.

DNA replication takes place at a Y-shaped structure called a replication fork. DNA polymerase help in produce two matching DNA stranges from a single DNA molecule. The leading strand is continuously extended from the primer by a DNA polymerase with high processivity, while the lagging strand is extended discontinuously from each primer forming Okazaki fragments. These Okazaki fragment are joined by the help of DNA ligase to form a continuous strand. Once the DNA in a cell is replicated, the cell can divide into two cells, each of which has an identical copy of the original DNA.

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