the change of Lk Tw Wr One strand of the DNA is broken. (2.5 marks) The helix is denatured by heat. (2.5 marks) DNA helicase is added to the DNA. (2.5 marks) This circular DNA has gone through DNA replication inside a cell. (2.5 marks)
Added by Gary G.
Step 1
- Lk (linking number) is no longer topologically constrained because a nick allows the strands to rotate past one another. - After the break, Tw and Wr can change freely as the molecule relaxes; upon resealing, Lk is restored to its original value, with Tw and Wr Show more…
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A closed circular DNA molecule in its relaxed form has a linking number (Lk) of 500. About how many base pairs are in this piece of DNA? How would the link (Lk), Twist (Tw), and writhe (Wr) of the DNA change under the following conditions. (Possible answers include: increase, decrease, remain the same, and undefined) (a) One strand of the DNA is broken. (b) The helix is denatured by heat. (c) DNA helicase is added to the DNA. (d) This circular DNA has gone through DNA replication inside a cell.
Josee P.
The two strands of a DNA double helix are separated by an enzyme called helicase at several origins of replication along the length of each chromosome. To keep the strands apart, single-stranded binding proteins bind and hold them away from each other, creating two replication -------------one at each end of a replication bubble. feel out the missing blank
Adi S.
The two strands of the DNA are complementary to each other such that at the end of the DNA one strand will be 3' paired with a 5' end. The two strands of the DNA are held together with hydrogen bonds. In DNA, A binds with T and G binds with C. Helicase unwinds the DNA for replication to begin. An RNA primer is created by enzyme primase which then supplies the (3' or 5') hydroxyl group used by DNA polymerase to start adding DNA nucleotides. The DNA strand is made from 5' to 3'. The lagging strand is made in short segments called Okazaki fragments. The leading strand is made in one continuous piece. After replication, the RNA primers are removed by enzyme RNase H and replaced with DNA nucleotides. The enzyme DNA ligase seals the nicks in the sugar-phosphate backbone after the RNA primers are removed. On linear chromosomes, the enzyme telomerase extends the ends by creating a repeating sequence of nucleotides which helps prevent loss of genetic material with each replication.
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