Chapter 5 — DNA and Genetic Information · Biology. These are 10 questions from the Magmo3 bank on this lesson, from easy to hard. Solve each one, then open "Show answer and explanation". Magmo3 has 35 questions on this lesson, each with an explanation.
How many DNA molecules result from the replication of a single DNA molecule?
Correct answer: (D) Two molecules
Explanation: Replication produces two identical molecules from the single molecule, and each one goes to one of the two resulting cells.
What is the shape of the DNA molecule in prokaryotes?
Correct answer: (D) Circular
Explanation: Bacterial DNA is a single circular molecule, unlike eukaryotes, whose DNA is linear.
During DNA replication, the nitrogenous base adenine (A) pairs with:
Correct answer: (C) Thymine
Explanation: According to the complementary base-pairing rule, A pairs with T through two hydrogen bonds.
At what point in the cell cycle does DNA replication occur?
Correct answer: (A) Before the cell divides
Explanation: The cell replicates its DNA before it divides so that each resulting cell receives a complete, identical copy.
The small circular DNA molecules found in some bacteria in addition to the main DNA are called:
Correct answer: (A) Plasmids
Explanation: Plasmids are small, extra circular DNA molecules found in some bacteria, separate from the main DNA.
What is the importance of complementary base pairing in ensuring the accuracy of replication?
Correct answer: (A) It determines the correct base opposite each base on the template
Explanation: Because A always pairs with T and G with C, the template exactly determines the order of nucleotides in the new strand, so the copy is accurate.
Why is DNA replication described as 'semiconservative'?
Correct answer: (B) Because each resulting molecule contains one original strand and one new strand
Explanation: In semiconservative replication each old strand acts as a template for a new strand, so each resulting molecule is half old and half new.
Compared with the leading strand, building the lagging strand needs:
Correct answer: (B) more primers and more joining by ligase
Explanation: The lagging strand is built in many fragments, and each fragment starts from its own primer. The fragments must then be joined by ligase. The leading strand grows continuously from a single start.
A bacterium lost its plasmid but kept growing and dividing normally, although it could no longer survive a certain antibiotic. What does this suggest?
Correct answer: (D) Essential genes are on the main chromosome, while plasmids carry useful extra genes
Explanation: The cell still lived and divided, so its essential genes are on the main circular chromosome. The plasmid carried an extra advantage, antibiotic resistance, and is still genetic material because it carries genes.
A new strand formed during replication has the sequence C-G-A-T-T. What is the sequence of the template strand it was built on?
Correct answer: (C) G-C-T-A-A
Explanation: The new strand is complementary to the template, so the template must be the complement of C-G-A-T-T, which is G-C-T-A-A (C with G and A with T).
The first 10 questions in every subject are free, each with an explanation.