IB Biology HL - Unit D1.1: DNA Replication

What is the process of DNA replication?

The production of exact copies of DNA with identical base sequences.

What is the semi-conservative nature of DNA replication?

Each daughter DNA molecule contains one strand of parent DNA and one newly synthesized strand.

Where does DNA replication occur in prokaryotic cells?

Before the cell divides by binary fission.

During which phase of the cell cycle does DNA replication occur in eukaryotic cells?

During the S stage of interphase.

What enzyme unwinds and unzips the DNA double helix during replication?

Helicase.

What role do single-strand binding (SSB) proteins play in DNA replication?

They prevent the separated DNA strands from rejoining.

What is the function of topoisomerase during DNA replication?

It relieves the strain caused by the unwinding of DNA.

What is a primer in DNA replication?

A short strand of RNA nucleotides created by primase to initiate DNA synthesis.

In which direction does primase synthesize the RNA primer?

In the 5' to 3' direction.

What is the role of DNA polymerase III in DNA replication?

It adds free DNA nucleotides to the growing strand, matching them with the template strand.

How does DNA polymerase III read the template strand?

In the 3' to 5' direction.

What are leading and lagging strands in DNA replication?

The leading strand is synthesized continuously towards the replication fork, while the lagging strand is synthesized discontinuously away from the fork.

What are Okazaki fragments?

Short segments of DNA synthesized on the lagging strand during replication.

What enzyme removes RNA primers during DNA replication?

DNA polymerase I.

What happens to the gaps between Okazaki fragments?

DNA polymerase I fills in the gaps with DNA nucleotides.

What is the origin of replication?

The point on the double helix where replication begins.

How many origins of replication are found in prokaryotic organisms?

A single origin of replication.

How do eukaryotic organisms differ in their origins of replication?

They have multiple origins of replication, allowing for replication bubbles.

What is the directionality of DNA polymerase during synthesis?

DNA polymerase synthesizes new DNA strands in the 5' to 3' direction.

What is the significance of complementary base pairing in DNA replication?

It ensures that the new strands are exact copies of the parent strands.

What is the role of helicase in DNA replication?

To separate the two strands of the DNA double helix.

What is the function of DNA ligase in DNA replication?

To join Okazaki fragments on the lagging strand.

What is DNA proofreading?

The process by which DNA polymerase checks and corrects errors during DNA synthesis.

What is the final product of DNA replication?

Two complete double helices, each with one parent strand and one new strand.

What ensures both daughter cells receive a full copy of DNA in prokaryotes?

DNA replication occurs before cell division.

What is the role of complementary base pairing in DNA replication?

It allows for the accurate synthesis of new DNA strands.

What enzyme seals gaps between DNA fragments during replication?

DNA ligase

What type of bond is formed between nucleotides in DNA?

Phosphodiester bond

In which direction are nucleic acids built?

5' to 3' direction

What is the error rate of DNA polymerase during replication?

1 in 10,000 base pairs

What is the final error rate of DNA replication after proofreading?

1 in 10 billion

What is the purpose of polymerase chain reaction (PCR)?

To amplify DNA sequences

What temperature is used to denature DNA in PCR?

90+ degrees Celsius

What happens during the annealing step of PCR?

Single-stranded DNA primers bind to target sequences

What is the optimal temperature for Taq polymerase during PCR?

72 degrees Celsius

Why is Taq polymerase used in PCR?

It is heat-resistant and does not denature during the process

What is gel electrophoresis used for?

To separate DNA fragments based on size

What charge does DNA carry due to its phosphate groups?

Negative charge

What is the role of restriction endonucleases in gel electrophoresis?

To cut DNA into fragments of different lengths

What is the first step in DNA profiling?

Collect DNA sample (e.g., bodily fluids)

What are Short Tandem Repeats (STRs)?

Fragments of DNA containing repeated base sequences used in DNA profiling

How many DNA fragments should match between a child and biological father in paternity testing?

50% of the child's fragments

What is the purpose of staining the gel in gel electrophoresis?

To make DNA fragments visible as bands under UV or blue light

What is the significance of the distance traveled by DNA fragments in gel electrophoresis?

It is inversely related to fragment size; smaller fragments move faster

What applications does PCR have?

Forensics, paternity testing, medical diagnostics, genetic disease screening, and research

What is the final step in DNA profiling?

Compare DNA profiles

What type of DNA regions are used for DNA profiling?

Non-coding regions

What is the role of restriction enzymes in DNA profiling?

To cut STR fragments for analysis

What happens to DNA fragments during gel electrophoresis?

They migrate towards the positive electrode

What is the purpose of PCR in forensic investigations?

To amplify DNA samples for comparison

What is the significance of environmental damage in DNA replication errors?

It can lead to mutations not caught by proofreading

What is the relationship between the size of DNA fragments and their migration distance in gel electrophoresis?

Smaller fragments travel farther than larger fragments