Biology 1.2

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Questions and Answers

What is the primary role of primers in PCR?

To separate DNA strands at high temperatures

To serve as starting points for DNA synthesis (correct)

To provide energy for DNA synthesis

To unwind the DNA double helix

Which factor is essential for successful DNA amplification using PCR?

Electrophoresis equipment

Availability of RNA primers

A stable DNA template (correct)

Presence of reverse transcriptase

Why are short DNA fragments generated during the lagging strand synthesis during replication?

Lagging strands do not require additional enzymes

The antiparallel structure dictates the synthesis direction (correct)

Polymerase can only work in the 3' to 5' direction

Nucleotides are added predominantly to the 5' end

What is the primary purpose of using primers in the Polymerase Chain Reaction (PCR)?

To provide starting points for DNA synthesis Signup and view all the answers

Which of the following is NOT a practical application of PCR?

Reversing mutations in DNA sequences Signup and view all the answers

In PCR, how are primers specifically chosen for a particular target sequence?

By matching them to unique sequences surrounding the target DNA Signup and view all the answers

What role does heat-tolerant DNA polymerase play in PCR?

It adds nucleotides to the growing DNA strand during amplification Signup and view all the answers

Which statement best describes the role of primers in DNA replication during PCR?

They initiate DNA synthesis by providing a free 3' hydroxyl group Signup and view all the answers

How can PCR be used in forensic science?

To amplify minute quantities of DNA from crime scenes Signup and view all the answers

Which of the following best describes thermal cycling in PCR?

Repeated heating and cooling to denature DNA and enable replication Signup and view all the answers

Which property of heat-tolerant DNA polymerase is particularly beneficial for PCR?

Its resilience to high temperatures without denaturing Signup and view all the answers

What is the role of primers in the Polymerase Chain Reaction (PCR)?

To provide a starting point for DNA polymerase to replicate DNA Signup and view all the answers

Which statement best describes the significance of using two primers in PCR?

They target opposing strands for replication Signup and view all the answers

What must occur prior to the binding of primers during the PCR process?

The DNA must be heated to break hydrogen bonds Signup and view all the answers

What is the expected outcome after one complete cycle of PCR?

Two identical copies of DNA Signup and view all the answers

Which of the following best describes how PCR can be applied in forensics?

It amplifies trace amounts of DNA for analysis Signup and view all the answers

Why is heat-tolerant DNA polymerase crucial in PCR?

It prevents denaturation during the heating cycle Signup and view all the answers

What is the main purpose of heating the DNA to temperatures between 92-98°C at the start of the PCR cycle?

To denature the DNA strands Signup and view all the answers

Study Notes

DNA Replication

DNA replication is essential before cell division to ensure each daughter cell receives an identical copy of the genetic material.
Five essential components for DNA replication are: DNA template, primers, free DNA nucleotides, enzymes, and ATP.

Stages of DNA Replication

The DNA unwinds, and hydrogen bonds between base pairs break, forming two template strands.
Nucleotides align with their complementary bases on the template strand to form new base pairs (hydrogen bonds form).
New sugar-phosphate backbones are formed on the new strands.
The final product is two identical DNA molecules, identical to the original parent DNA.

Primers in DNA Replication

Primers are short strands of nucleotides that initiate DNA replication.
They are crucial because DNA polymerase can only add nucleotides to an existing chain, and primers provide this starting point.

DNA Replication Enzymes

DNA polymerase is an enzyme that adds new nucleotides in the 5' to 3' direction to the leading strand continuously.
DNA polymerase has to add nucleotides in fragments to the lagging strand.
Ligase joins the Okazaki fragments, completing the lagging strand.
These are involved in DNA replication.

Direction of Replication

DNA replication is always in the 5' to 3' direction.
The leading strand is built continuously in the 5' to 3' direction along, which is the direction of replication. This is due to DNA Polymerase working in this direction.
The lagging strand is built discontinuously in short fragments (Okazaki fragments) in the opposite direction.

Polymerase Chain Reaction (PCR)

PCR is a technique used to amplify DNA in a laboratory.
A single DNA strand can be duplicated into millions, allowing for analysis.
The purpose is to make multiple copies of a specific DNA sequence.
The process involves a series of temperature changes to allow for DNA strand separation (denaturation), primer annealing, and DNA synthesis (extension).
Heat-tolerant DNA polymerase is crucial because it can withstand the high temperatures needed for DNA denaturation.
Primers are specific sequences that bind to the target DNA to be replicated.
Thermal cycling involves repeatedly heating and cooling the DNA to complete each PCR replication cycle.

PCR Applications

PCR is used to amplify small amounts of DNA from a variety of sources, such as crime scenes, blood, or tissue samples.
It is used in genetic testing and diagnostics, such as prenatal genetic testing or paternity testing.

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