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IB Biology D1.1: DNA Replication — Practice Questions & Answers
IB Biology D1.1 DNA replication study notes: semi-conservative copying, complementary base pairing, helicase and DNA polymerase, and the role of PCR.
Here are 10 practice questions with full answers and explanations.
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Practice questions with answers
1
Multiple choice
Which of the following statements accurately explain why DNA replication is a necessary process for multicellular organisms?
I. It ensures that each new cell produced during growth and development receives a complete and identical set of genetic instructions
II. It is essential for replacing old, damaged, or dead cells and for repairing tissues throughout the organism's life
III. It is a prerequisite for cell division (mitosis and meiosis), allowing for the formation of new cells and gametes
IV. Its primary role is to generate immediate energy for cellular metabolic activities, similar to ATP synthesis
I and II only
I, II, and III only
II and IV only
All I, II, III, and IV.
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Why DNA replication is needed for growth, tissue repair, and passing complete genetic information to daughter cells.
2
Multiple choice
What does the semi-conservative nature of DNA replication ensure?
I. Each new DNA molecule consists of one strand from the original (parental) molecule and one newly synthesized strand.
II. The accurate transmission of genetic information from a parent cell to its two daughter cells.
III. The preservation of the original genetic sequence across generations of cells.
I and II only
I and III only
II and III only
All I, II and III
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Why Semi-conservative replication ensures each new molecule keeps one parental strand, preserving genetic information accurately.
3
Multiple choice
What is the role of helicase in DNA replication?
Unwinding and breaking hydrogen bonds between DNA strands.
Synthesizing new DNA strands.
Joining DNA fragments.
Proofreading DNA sequences.
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Why Helicase unwinds the double helix and breaks the hydrogen bonds between complementary strands.
4
Multiple choice
What is the general role of DNA polymerase?
Synthesizing new DNA strands.
Unwinding DNA.
Joining RNA fragments.
Breaking peptide bonds.
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Why DNA polymerase synthesises new DNA strands by adding nucleotides complementary to the template.
5
Multiple choice
What is the purpose of the polymerase chain reaction (PCR)?
To amplify DNA.
To separate DNA fragments.
To synthesize proteins.
To modify DNA sequences.
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Why PCR amplifies a target DNA sequence, producing many copies from a small starting sample.
6
Multiple choice
What is Taq polymerase used for in PCR?
Synthesizing DNA at high temperatures.
Unwinding DNA.
Joining DNA fragments.
Breaking peptide bonds.
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Why Taq polymerase is heat-stable, allowing it to synthesise DNA at the high temperatures used in PCR.
7
Multiple choice
Which of the following statements accurately describe the basis of separation of DNA fragments during gel electrophoresis?
I. DNA molecules are negatively charged due to their phosphate backbone, causing them to migrate towards the positive electrode
II. The gel matrix acts as a sieve, allowing smaller DNA fragments to move through its pores more easily and thus migrate faster and further
III. Separation is primarily based on the length (size) of the DNA fragments, with shorter fragments traveling a greater distance than longer ones
IV. Fragments are separated based on their specific nucleotide base sequence, allowing for precise identification of genes
I and II only
I, II, and III only
II and IV only
All I, II, III and IV.
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Why Gel electrophoresis separates fragments by size and charge as they migrate through the gel toward the positive electrode.
8
Multiple choice
What is one application of PCR and gel electrophoresis?
DNA profiling for paternity and forensic investigations.
Protein synthesis.
RNA transcription.
Cellular respiration.
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Why Combining PCR and gel electrophoresis enables DNA profiling for paternity testing and forensic identification.
9
Multiple choice
What does increasing the number of markers used in DNA profiling reduce?
The probability of a false match.
The speed of gel electrophoresis.
The accuracy of PCR.
The size of DNA fragments.
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Why Using more markers lowers the probability that two unrelated individuals share the same profile by chance.
10
Multiple choice
What is the role of primers in PCR?
Defining the DNA sequence to be amplified.
Unwinding DNA.
Joining DNA fragments.
Breaking peptide bonds.
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Why Primers are short sequences that flank and define the region of DNA to be amplified.
Key terms in DNA Replication
Semi-conservative replication: Replication in which each new DNA molecule contains one original template strand and one new strand.
Complementary base pairing: The specific pairing of A with T and C with G by hydrogen bonds, ensuring each strand specifies its partner.
Template strand: An original DNA strand whose base sequence directs the synthesis of a new complementary strand.
Helicase: An enzyme that unwinds the double helix and breaks the hydrogen bonds between bases to separate the strands.
DNA polymerase: An enzyme that adds free DNA nucleotides to a template strand by complementary base pairing and links them together.
DNA nucleotide: The monomer of DNA, made of a deoxyribose sugar, a phosphate group and one of the bases A, T, C or G.
Replication fork: The Y-shaped region where the double helix has been separated and new strands are being synthesised.
Polymerase chain reaction (PCR): A laboratory technique that rapidly makes many copies of a target DNA sequence through repeated cycles of denaturation, annealing and elongation.
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