GED Science : DNA and DNA Repair

Study concepts, example questions & explanations for GED Science

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Example Questions

Example Question #1 : Dna And Dna Repair

Which of the following is NOT common to both DNA and RNA?

Possible Answers:

Both have a sugar phosphate backbone

Both use thymine as a nitrogenous base

Both use adenine as a nitrogenous base

Both are composed of nucleotides

Correct answer:

Both use thymine as a nitrogenous base

Explanation:

RNA and DNA have many similarities in structure. They are both nucleic acids, meaning they are polymers of nucleotides; the structure of both DNA and RNA is made by bonding many nucleotide units into a long polymer chain. These chains are created by bonding in the sugar phosphate backbone. Each nucleotide contains a sugar, a phosphate, and a nitrogenous base. When the sugars and phosphates bind, nucleotides are strung together to create the nucleic acid chain.

There are two key structural differences between DNA and RNA. The first is the identity of the sugar used in the sugar phosphate backbone. DNA uses deoxyribose, while RNA uses ribose. Both are pentose sugars, meaning they have five carbons, but the 2' carbon in RNA has a hydroxyl group that is absent in DNA. The second major difference is the identity of the nitrogenous bases used to code genetic information. DNA uses cytosine, guanine, adenine, and thymine. RNA uses cytosine, guanine, adenine, and uracil. Thymine will not be found in RNA and uracil will not be found in DNA.

Example Question #2 : Dna And Dna Repair

What does it mean to say that DNA replication is semiconservative?

Possible Answers:

Only one DNA strand is replicated at a time

DNA replication occurs spontaneously in aqueous solutions

Daughter DNA molecules have one old strand from the parent molecule and one newly synthesized strand

DNA replication has a leading strand, which is synthesized continuously, and a lagging strand, which is synthesized in fragments

Correct answer:

Daughter DNA molecules have one old strand from the parent molecule and one newly synthesized strand

Explanation:

DNA replication is defined as being semiconservative. This statement means that when a DNA molecule undergoes replication, the DNA helix unwinds and each strand serves as a template for the new strand to be created. Once a new DNA molecule has been created, it is composed of both an old strand (template), and the newly created strand, thus making a new double helix.

While the answer choice about leading and lagging strands is a true statement with regard to DNA replication, it is unrelated to the semiconservative nature of the process.

Example Question #1 : Dna, Rna, And Proteins

During DNA replication, primase creates a(n) __________ which serves as a site for __________ to attach and begin strand synthesis.

Possible Answers:

DNA primer . . . RNA polymerase

DNA primer . . . DNA polymerase III

RNA primer . . . DNA polymerase III

RNA primer . . . DNA polymerase I

Correct answer:

RNA primer . . . DNA polymerase III

Explanation:

During DNA replication, DNA polymerase III needs a site of attachment in order to begin DNA strand synthesis. This template is provided by primase, which lays down an RNA primer for DNA polymerase III to attach.

RNA polymerase is not involved in DNA replication (it is involved in translation), and DNA polymerase I is used to replace the RNA primers with DNA nucleotides.

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