DNA Replication Overview

DNA replication where each new DNA molecule contains one original strand and one newly synthesized strand.

A type of DNA replication where the original DNA molecule remains intact, and a completely new copy is made.

A type of DNA replication where the original DNA molecule is broken down into small pieces, and each new DNA molecule is made up of a mixture of old and new DNA fragments.

A type of DNA structure where the two strands of the DNA helix are intertwined, like a twisted ladder.

Enzymes that help to unwind and separate the two strands of the DNA helix during DNA replication.

DNA molecules that are circular in shape, such as those found in bacteria and some viruses.

The process of copying DNA, which is essential for cell division and growth.

The two strands of DNA are separated and each serves as a template for the synthesis of a new strand. This ensures that each daughter cell receives a complete copy of the genetic information.

A method used to separate molecules based on their density. Heavier molecules settle at the bottom of the tube, while lighter molecules remain near the top.

A commonly used chemical in density gradient centrifugation. It forms a density gradient when centrifuged, allowing molecules to separate based on their weight.

An isotope of nitrogen with an atomic weight of 15. It is heavier than the common nitrogen isotope (14N).

The nitrogen component of DNA bases, which can be labelled with either 14N or 15N allowing for tracking of DNA molecules in experiments.

The experiment conducted by Meselson and Stahl in 1959 to determine the mode of DNA replication.

The process of unwinding the DNA double helix, exposing the individual strands for replication.

The rate at which a circular DNA molecule would have to rotate if it were unwound linearly for replication.

Enzymes that are responsible for relieving the torsional stress caused by DNA supercoiling during replication. They act by temporarily breaking and resealing DNA strands, allowing one strand to pass through the other.

The winding or coiling of double-stranded DNA upon itself, creating a more compact and tightly wound structure. This can occur during DNA replication, as unwinding one part of the strand creates tension elsewhere.

These topoisomerases work by cleaving one of the DNA strands, allowing the other strand to pass through the break, and then resealing the break.

These topoisomerases act by cleaving both strands of DNA simultaneously, forming a 'gate' that allows another portion of the DNA strand to pass through before resealing the break.

The complete breaking of one DNA strand (G segment) to allow another (T segment) to pass through the break.

The unwinding of the DNA helix, breaking the hydrogen bonds between the base pairs, to expose the individual strands for replication.

The enzyme responsible for building new DNA strands during replication. It reads the existing strand and adds complementary nucleotides to the newly synthesized strand.

Enzymes that break the hydrogen bonds between complementary base pairs, allowing for the separation of the DNA double helix.

Short DNA fragments synthesized on the lagging strand during replication, due to the discontinuous nature of synthesis.

DNA synthesis relies on a template strand of DNA to create a new complementary strand.

DNA synthesis always occurs in the 5' to 3' direction, meaning new nucleotides are added to the 3' end of the growing strand.

A primer is a short sequence of RNA that initiates DNA synthesis. It provides a starting point for DNA polymerase.

DNA polymerases have exonuclease activity, which allows them to remove nucleotides from DNA. This activity is crucial for proofreading and repair.

DNA polymerase's ability to remove incorrect nucleotides during synthesis, ensuring accuracy.

A special enzyme that joins Okazaki fragments together on the lagging strand during DNA replication.

The enzyme responsible for removing RNA primers from Okazaki fragments during DNA replication.

A specialized endonuclease that removes the 5' flap created during Okazaki fragment processing in eukaryotes.

Proteins that bind to and protect single-stranded DNA during replication, preventing degradation and re-attachment.

The leading strand is synthesized continuously in the 5' to 3' direction, following the replication fork.

A short RNA sequence that provides a starting point for DNA polymerase to begin synthesis.

The lagging strand is synthesized discontinuously in short fragments called Okazaki fragments, moving away from the replication fork.

The lagging strand is synthesized in short fragments called Okazaki fragments, each requiring a separate primer to initiate synthesis.

The leading strand is synthesized continuously in the 5' to 3' direction, following the replication fork. It requires only one primer to initiate synthesis.

The lagging strand is synthesized discontinuously in the 5' to 3' direction, moving away from the replication fork. It requires multiple primers for each Okazaki fragment.

Short sequences of RNA that provide a starting point for DNA polymerase to begin synthesis.

A specialized endonuclease that removes the 5' flap created during Okazaki fragment processing in eukaryotes.

A special enzyme that extends the parent DNA by adding the sequence TTAGGG several times, preventing the ends of chromosomes from being shortened.

The final Okazaki fragment cannot be made because its priming site would be after the end of the parent molecule; this leads to DNA molecules getting shorter with each replication.

The lagging strand is synthesized discontinuously in fragments because DNA polymerase can only synthesize in one direction (5' to 3').

An endonuclease that cuts the 5' end of the RNA primer located at the beginning of an Okazaki fragment.

Enzymes that join Okazaki fragments together on the lagging strand during DNA replication.

The leading strand is extended by more DNA synthesis, while the lagging strand has to be made in sections (Okazaki fragments) because of the antiparallel nature of DNA.

The ends of chromosomes are protected and maintained by a special enzyme called telomerase. Telomerase adds repetitive DNA sequences to the ends of chromosomes, preventing them from shortening during DNA replication.

Most cells in our body lack telomerase, leading to a gradual shortening of chromosome ends with each cell division. This shortening eventually triggers cellular senescence, where cells stop dividing and become inactive.

Telomeres are specialized structures located at the ends of chromosomes. They are composed of repetitive DNA sequences and protect the ends of chromosomes from degradation and fusion.

The S phase of the cell cycle is the stage during which the cell replicates its entire DNA content, effectively doubling its genetic material before cell division.

The process of replicating DNA involves the unwinding of the double helix structure, separating the two strands, and using each strand as a template to synthesize a new complementary strand. This results in two identical DNA molecules.

Specialized enzymes called DNA polymerases are responsible for synthesizing new DNA strands during replication. They read the existing template strand and add complementary nucleotides, forming a new, identical DNA strand.

The process of DNA replication involves the formation of two replication forks, where the DNA double helix is unwound and separated. These forks move along the DNA molecule, creating two new strands with the help of DNA polymerase.

DNA replication is a semi-conservative process, meaning each newly formed DNA molecule contains one original strand and one newly synthesized strand. This ensures that each daughter cell receives a complete and accurate copy of the genetic information.