DNA Replication Flashcards

Flashcards about DNA Replication

Continuity and Change in Living Things

Living things have mechanisms for maintaining equilibrium and for bringing about transformation. Environmental change is a driver of evolution by natural selection.

What is DNA replication?

DNA replication is the production of exact copies of DNA with identical base sequences.

Describe the result of DNA replication.

Each molecule formed by replication consists of one new strand and one old strand conserved from the parent DNA molecule, resulting in two DNA molecules each with one original and one newly synthesized strand.

What processes require DNA replication?

Growth, reproduction, and tissue repair.

How do multicellular organisms grow?

Multicellular organisms increase their size by increasing their number of cells.

Why is DNA replication important for reproduction?

Offspring need copies of the base sequences of their parents, so parents must replicate their DNA when reproducing sexually or asexually.

Why is DNA replication important for tissue replacement and repair?

Multicellular organisms require cell division in tissues where cells have been lost or damaged.

Describe the process of DNA replication using a template.

The two strands of DNA come apart, and each strand acts as a template for DNA replication. The new strands are formed by adding nucleotides one by one and linking them together.

Why is DNA replication called semi-conservative?

When replication is complete, there are two DNA molecules, both composed of an original strand and a newly synthesized strand. For this reason, DNA replication is referred to as semi-conservative.

What experiment proved that DNA replication is semi-conservative?

Experiments (Meselson-Stahl experiment) proved that DNA replication is semi-conservative.

What acts as the template for new DNA strands?

The DNA base sequence of the parent strands act as template for the new strands.

Which bases pair together in DNA?

Adenine pairs only with Thymine, and Cytosine pairs only with Guanine.

Why is complementary base pairing important?

Complementary base pairing ensures a high degree of accuracy when strands are assembled.

What is the role of helicase in DNA replication?

Helicase separates the two strands of a DNA molecule by breaking hydrogen bonds.

What is the role of DNA polymerase in DNA replication?

DNA polymerase adds free nucleotides one by one in positions on the template strand where hydrogen bonds between complementary bases can form.

What is PCR?

The polymerase chain reaction (PCR) is an automated procedure used to copy specific sections of DNA molecules in a cell sample.

What is the use of Thermus aquaticus in PCR?

Thermus aquaticus' polymerase is often abbreviated to 'Taq’ and is frequently used in polymerase chain reaction (PCR) because the enzyme withstands the high temperatures required in this process without being destroyed (denatured).

How does PCR amplify DNA?

Each reaction cycle doubles the amount of DNA – a standard PCR sequence of 30 cycles creates over 1 billion copies.

What is gel electrophoresis used for?

Gel electrophoresis separates DNA molecules by length.

What techniques are required to establish a DNA profile?

PCR and gel electrophoresis are required to establish a DNA profile or fingerprint.

What is DNA profiling?

Comparing short DNA sequences of different individuals and looking for matches in fragment length.

What are the main applications of DNA profiling?

Crime scene/forensic investigations and paternity investigations.

What are STRs and VNTRs?

STRs and VNTRs are short repetitive sequences on the DNA which differ slightly between individuals and therefore allow a specific DNA fingerprint to be produced for every person.

What is the definition of VNTR?

Variable Number Tandem Repeats, VNTR (minisatellites) have longer base sequences (hundreds of base pairs) repeated few times.

What is the definition of STR?

Short Tandem Repeats, STR (microsatellites) have shorter base sequences (2-6 base pairs) repeated many times.

What are the 5' and 3' ends of a nucleotide?

The carbon atom to which the phosphate group is attached is called C5 and marks the 5’ end of the nucleotide. The carbon atom with a free OH (hydroxyl) group on the pentose sugar is the C3, and therefore marks the 3’ end of the nucleotide.

In what direction does DNA replication occur, and why?

When a new DNA strand is synthesized, the direction of replication will always occur from 5’ to 3’ direction – new nucleotides can only join at the 3’ end.

How does DNA polymerase form bonds between nucleotides?

Once DNA polymerase has recognized the 3’ end of a nucleotide, it helps the formation of a covalent (phosphodiester bond) between previous nucleotide and the free one.

How does replication differ on the leading and lagging strands?

It is continuous on the leading strand but discontinuous on the lagging strand.

Okazaki fragments

Short DNA fragments synthesized on the lagging strand in the 5’ to 3’ direction during DNA replication.

Helicase function

Helicase unwinds the DNA double helix by breaking the hydrogen bonds between base pairs, creating the replication fork.

DNA Polymerase III Function

Synthesizes new DNA strands by adding nucleotides in the 5’ to 3’ direction, primarily responsible for elongating the leading strand and Okazaki fragments on the lagging strand.

DNA Primase Function

Synthesizes short RNA primers that provide a starting point for DNA Polymerase III to begin DNA synthesis.

DNA Polymerase I Function

Removes RNA primers and replaces them with DNA nucleotides.

DNA Ligase Function

Joins Okazaki fragments by forming phosphodiester bonds, sealing gaps in the sugar-phosphate backbone.

RNA Primers

Short RNA sequences synthesized by RNA primase that serve as starting points for DNA polymerization.

How does DNA replication differ in prokaryotes and eukaryotes?

In prokaryotes there is one origin of replication. In eukaryotes DNA replication is initiated at many points.

How is DNA proofread in prokaryotes?

In prokaryotes, DNA polymerase III takes over repair and proofreading immediately after replication.