A covalent bond forms between the carbon at the 3′ position of a nucleotide and the phosphate group at the 5′ position of the next nucleotide.
RNA usually consists of a single polynucleotide chain.
DNA, on the other hand, consists of two polynucleotide chains. The two DNA chains, or strands, are oriented in opposite directions and held together by hydrogen bonds between the nitrogenous bases on opposite strands.
Nucleotides are composed of a pentose sugar, a nitrogenous base, and a phosphate group.
It untwists the double helix and separates the two DNA strands. By pulling apart and untwisting the DNA strands, helicase makes them available for replication.
Each new double helix consists of one old and one new strand.
What process repairs damage to a preexisting double helix?
nucleotide excision repair
In nucleotide excision repair, a section of DNA containing the damage is removed, and the gap is then filled in and completed by DNA polymerase and DNA ligase.
What are the repetitive DNA sequences present at the ends of eukaryotic chromosomes called?
Telomeres consist of many copies of a short DNA sequence that is bound by specific proteins.
What are chromosomes made of?
DNA and proteins
Long DNA molecules are associated with proteins that allow DNA to coil and pack.
Which of the following is true of DNA during interphase?
It exists as chromatin and is unavailable for gene expression.
Chromatin is the term for the loosely coiled DNA observed in cells during interphase. Even during interphase, however, parts of the chromosome may still be rather tightly coiled and packed.
What catalyzes DNA synthesis?
DNA polymerase
Which of the following statements about DNA synthesis is true?
Primers are short sequences that allow the initiation of DNA synthesis.
When a primer is added to a single strand of DNA, DNA polymerase can start adding nucleotides to synthesize a complementary strand.
Which part of a deoxynucleoside triphosphate (dNTP) molecule provides the energy for DNA synthesis?
Phosphate groups
The potential energy stored in the bonds of the phosphates provides the energy for DNA synthesis
Which of the following enzymes creates a primer for DNA polymerase?
This RNA polymerase synthesizes an RNA primer antiparallel to the template DNA strand.
Which of the following statements about Okazaki fragments in E. coli is true?
They are formed on the lagging strand of DNA.
While DNA is synthesized continuously on the leading strand, Okazaki fragments are formed on the lagging strand because DNA synthesis always proceeds in the 5′ to 3′ direction.

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