DNA Replication and Cell Cycle Overview

<p>G1 and G2 phases. (C)</p> Signup and view all the answers

<p>Eukaryotes. (B)</p> Signup and view all the answers

<p>Conservative model (C)</p> Signup and view all the answers

<p>Semiconservative model (A)</p> Signup and view all the answers

<p>Dispersive model (C)</p> Signup and view all the answers

<p>Meselsohn &amp; Stahl experiment (D)</p> Signup and view all the answers

<p>The conservative model keeps both strands entirely parental. (C)</p> Signup and view all the answers

<p>A-T rich sequence (A)</p> Signup and view all the answers

<p>10,000 ORI sites (C)</p> Signup and view all the answers

<p>Theta (Θ) (C)</p> Signup and view all the answers

<p>Multiple replication units (B)</p> Signup and view all the answers

<p>DNA A (D)</p> Signup and view all the answers

<p>To provide a starting point for DNA polymerase to add nucleotides (D)</p> Signup and view all the answers

<p>5' to 3' (D)</p> Signup and view all the answers

<p>Phosphodiester bond (C)</p> Signup and view all the answers

<p>To synthesize short RNA sequences as primers (D)</p> Signup and view all the answers

<p>An RNA primer (B)</p> Signup and view all the answers

<p>To initiate the synthesis of DNA strands (A)</p> Signup and view all the answers

<p>Okazaki fragments (C)</p> Signup and view all the answers

<p>The leading strand is synthesized continuously, while the lagging strand is formed in fragments. (A)</p> Signup and view all the answers

<p>DNA ligase (D)</p> Signup and view all the answers

<p>100-200 bases (A)</p> Signup and view all the answers

<p>Each DNA strand is replicated in opposite directions from a single origin. (D)</p> Signup and view all the answers

<p>To correct mismatched bases (A)</p> Signup and view all the answers

<p>3' to 5' exonuclease activity (C)</p> Signup and view all the answers

<p>By reducing the error rate to about one per billion base pairs (A)</p> Signup and view all the answers

<p>3' to 5' (D)</p> Signup and view all the answers

<p>Correction of replication errors (C)</p> Signup and view all the answers

<p>5' to 3' exonuclease activity (A)</p> Signup and view all the answers

<p>Remove RNA primers and add DNA nucleotides at the 3’ end (A)</p> Signup and view all the answers

<p>Sealing nicks between Okazaki fragments (C)</p> Signup and view all the answers

<p>It can remove RNA primers and extend DNA strands. (B)</p> Signup and view all the answers

<p>By joining Okazaki fragments (D)</p> Signup and view all the answers

<p>To synthesize a short RNA primer (D)</p> Signup and view all the answers

<p>A template DNA strand and RNA primer (B)</p> Signup and view all the answers

<p>5′ → 3′ direction (D)</p> Signup and view all the answers

<p>To join two DNA fragments together (B)</p> Signup and view all the answers

<p>Serving as a starting point for DNA polymerase (C)</p> Signup and view all the answers

<p>DNA Polymerase III (B)</p> Signup and view all the answers

<p>To prevent DNA polymerase from dissociating from the DNA strand (A)</p> Signup and view all the answers

<p>DNA Polymerase γ (B)</p> Signup and view all the answers

<p>Eukaryotic DNA polymerases are more than a dozen types. (D)</p> Signup and view all the answers

<p>Removing RNA primers and replacing them with DNA (D)</p> Signup and view all the answers

<p>Opens up the DNA at the replication fork (B)</p> Signup and view all the answers

<p>Primase (C)</p> Signup and view all the answers

<p>Hold DNA polymerase III in place (A)</p> Signup and view all the answers

<p>Prevents supercoiling in the DNA ahead of the replication fork (D)</p> Signup and view all the answers

<p>DNA Ligase (D)</p> Signup and view all the answers

<p>They loosen nucleosome packing. (D)</p> Signup and view all the answers

<p>They are reassembled on the new strands. (B)</p> Signup and view all the answers

<p>They do not exist in bacteria. (A)</p> Signup and view all the answers

<p>They are temporarily disassembled. (D)</p> Signup and view all the answers

<p>They provide structural stability for linear DNA. (D)</p> Signup and view all the answers

<p>Protecting important genetic information (D)</p> Signup and view all the answers

<p>TTAGGG (D)</p> Signup and view all the answers

<p>There is no 3' end available for nucleotide addition (B)</p> Signup and view all the answers

<p>Replicating telomeres (C)</p> Signup and view all the answers

<p>They produce shorter DNA molecules with uneven ends (C)</p> Signup and view all the answers

<p>DNA damage (C)</p> Signup and view all the answers

<p>Mitosis Promoting Factor (MPF) (C)</p> Signup and view all the answers

<p>Serves as a Stop signal (A)</p> Signup and view all the answers

<p>M checkpoint (A)</p> Signup and view all the answers

<p>It is regulated by protein levels (A)</p> Signup and view all the answers

<p>Exposure to certain chemicals or radiation (D)</p> Signup and view all the answers

<p>To correct DNA damage (A)</p> Signup and view all the answers

<p>S phase (A)</p> Signup and view all the answers

<p>Cellular aging and disease development (D)</p> Signup and view all the answers

<p>It can spontaneously incur damage (C)</p> Signup and view all the answers

<p>Deamination and alkylation (B)</p> Signup and view all the answers

<p>Removal of the damaged base (A)</p> Signup and view all the answers

<p>Conversion of base C to base U (B)</p> Signup and view all the answers

<p>G/C to A/T (B)</p> Signup and view all the answers

<p>DNA mutations (D)</p> Signup and view all the answers

<p>Pyrimidine dimers (C)</p> Signup and view all the answers

<p>Potential mutations leading to cancer (C)</p> Signup and view all the answers

<p>Xeroderma pigmentosum (A)</p> Signup and view all the answers

<p>T-T dimers (C)</p> Signup and view all the answers

<p>Recognition of DNA damage (C)</p> Signup and view all the answers

<p>Deamination (A)</p> Signup and view all the answers

<p>C to U (D)</p> Signup and view all the answers

<p>Removal of the damaged base (A)</p> Signup and view all the answers

<p>G/C to A/T (D)</p> Signup and view all the answers

<p>Prevention of all mutations (C)</p> Signup and view all the answers

The sequence of events that leads to cell division in eukaryotic cells, including the stages of Interphase (G1, S, G2) and the M stage (Mitosis).

DNA replication happens during the S phase of Interphase in eukaryotic cells. This phase doubles the cell's DNA content.

Identical copies of a chromosome formed during DNA replication, joined at the centromere.

Process of DNA replication in prokaryotes that differ significantly from the eukaryotic cell cycle. No Interphase, no Mitosis. Divides by Binary Fission.

The region where two sister chromatids are joined together on replicated chromosomes.

The process of creating two identical DNA molecules from one original DNA molecule. It involves the separation of the original strands and the synthesis of new complementary strands.

A model of DNA replication where the original DNA molecule remains intact, and the newly synthesized DNA is entirely new. In other words, one daughter DNA is fully parental and the other is fully new.

A model of DNA replication where the original DNA molecule is broken into segments, and the new DNA is a mix of old and new segments. In other words, each daughter DNA has a mix of original and new pieces.

A model of DNA replication where each new DNA molecule contains one original strand and one newly synthesized strand. In other words, each daughter DNA has one parental strand.

An experiment that proved the semiconservative model of DNA replication. It used isotopes of nitrogen to distinguish between old and new DNA strands.

The specific DNA sequence where DNA replication starts in both prokaryotes and eukaryotes.

An initiator protein in bacteria that identifies and binds to the ORI site, initiating DNA unwinding.

A structure formed during DNA replication where the DNA strands separate, creating a bubble-like region where new DNA is synthesized.

Two Y-shaped structures that form at the ends of a replication bubble, where new DNA is synthesized.

DNA replication that occurs simultaneously in both directions away from the origin of replication (ORI).

DNA replication where each new DNA molecule consists of one original strand from the parent molecule and one newly synthesized strand.

The enzyme responsible for synthesizing new DNA strands during replication. It adds nucleotides to the 3' end of an existing strand.

A short RNA sequence that serves as a starting point for DNA polymerase to begin synthesizing a new DNA strand.

DNA polymerase can only add nucleotides to the 3' end of an existing strand, thus DNA synthesis proceeds in this direction.

The process of extending the new DNA strand by adding nucleotides, one at a time, to the free 3' end.

The new DNA strand synthesized continuously in the 5' to 3' direction. It grows in the same direction as the replication fork.

The new DNA strand synthesized discontinuously in short fragments called Okazaki fragments. It grows in the opposite direction of the replication fork.

Short segments of DNA synthesized on the lagging strand, joined together by DNA ligase to create a continuous strand.

The enzyme that seals the gaps between Okazaki fragments, creating a continuous strand of DNA.

DNA polymerase can check the newly added nucleotide and replace it with the correct one if it's wrong.

DNA polymerase removes a wrong nucleotide by using its exonuclease activity, chewing it off from the 3' end.

The accuracy of DNA replication, meaning very few errors are made.

The number of errors made during DNA replication.

DNA replication has an error rate of around 1 in a billion base pairs.

DNA polymerase I removes RNA primers using its 5' to 3' exonuclease activity, preparing the DNA strand for ligation.

DNA polymerase I can remove RNA primers with its 5' to 3' exonuclease activity and also add DNA nucleotides to the 3' end of a growing chain.

DNA ligase joins the Okazaki fragments on the lagging strand, creating a continuous DNA strand.

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

Okazaki fragments are needed on the lagging strand because DNA polymerase can only synthesize DNA in the 5' to 3' direction, and the lagging strand is synthesized in the opposite direction of the replication fork.

An RNA polymerase enzyme that synthesizes short RNA primer sequences (~10 bases) on the template DNA strand during DNA replication.

Short fragments of DNA synthesized on the lagging strand during DNA replication. They are joined together by DNA ligase to create a continuous strand.

The primary enzyme responsible for DNA replication in bacteria. It replicates DNA at a rate of about 50,000 base pairs per minute.

A protein that binds to DNA polymerase III and prevents it from detaching from the DNA template strand during replication.

Eukaryotes have multiple DNA polymerases, with specific roles in replication.

An enzyme that unwinds the DNA double helix at the replication fork, separating the two strands to create a template for replication.

An enzyme that relieves the tension ahead of the replication fork by cutting and rejoining the DNA strands, preventing supercoiling.

Proteins that bind to the separated DNA strands at the replication fork, keeping them from re-annealing (re-binding) and preserving the template for replication.

In eukaryotic cells, specialized proteins loosen the tightly packed chromatin structure (nucleosomes) to allow access for DNA replication machinery.

After DNA replication, nucleosomes are reassembled on the newly synthesized DNA strands, ensuring proper packaging and function.

Nucleosomes need to be removed during replication because they act as roadblocks for the replication machinery, preventing the enzymes involved from accessing the DNA.

Specialized proteins help guide the reassembly of nucleosomes on the newly synthesized DNA strands, ensuring proper chromatin structure is restored.

Prokaryotic cells do not have nucleosomes, as their DNA is not packaged in the same way as eukaryotic DNA.

A specialized region at the end of a linear chromosome, made of repetitive DNA sequences, that protects the chromosome from degradation and prevents it from fusing with other chromosomes.

The inability of DNA polymerase to replicate the very end of a linear DNA strand during normal replication, resulting in a progressive shortening of chromosomes after each round of replication.

An enzyme that adds repetitive DNA sequences (TTAGGG) to the ends of chromosomes, compensating for the loss of DNA during replication, and maintaining telomere length.

Telomeres protect the ends of chromosomes from degradation and prevent them from fusing with other chromosomes. They are like caps that keep the chromosomes intact.

Telomerase acts as a reverse transcriptase, using its own RNA template to add telomeric repeats to the ends of chromosomes, effectively replacing the lost DNA and maintaining telomere length.

Points in the cell cycle where the cell checks for essential conditions before proceeding to the next phase. They ensure accurate DNA replication and chromosome segregation.

The first major checkpoint in the cell cycle, checking for DNA damage. If damage is detected, the cell cycle arrests and the cell attempts repair before proceeding.

The second major checkpoint in the cell cycle, verifying that DNA replication is complete and accurate. It ensures all chromosomes are duplicated correctly.

The final checkpoint in the cell cycle, ensuring that all replicated chromosomes are properly attached to the mitotic spindle before cell division.

A protein kinase that acts as a 'Go' signal at the G2 checkpoint. High MPF levels trigger the transition from G2 to M phase of the cell cycle.

DNA repair mechanisms are essential for maintaining the integrity of the genetic code and preventing mutations that can lead to diseases like cancer. They fix damage to DNA caused by replication errors, environmental factors, or other stressors.

Major types of DNA repair include: Base Excision Repair, Nucleotide Excision Repair, Mismatch Repair, and Double Strand Break Repair. Each mechanism targets specific types of DNA damage.

BER removes damaged or incorrect bases from DNA. It involves a series of enzymes that recognize the damaged base, excise it, and then replace it with the correct base.

NER repairs larger lesions in DNA, such as those caused by UV radiation. It involves a series of enzymes that cut out the damaged segment and replace it with a new, correct segment.

MMR corrects mismatched base pairs that arise during DNA replication. It involves a series of enzymes that identify the mismatch, excise the incorrect base, and then replace it with the correct base.

A DNA repair mechanism that removes damaged or incorrect bases from DNA. It involves a series of enzymes that recognize, excise, and replace the damaged base with the correct one.

A spontaneous chemical reaction that removes an amino group from a base. It can convert cytosine (C) to uracil (U), leading to a G/C to A/T base pair conversion.

A spontaneous chemical reaction that adds an alkyl group to a base, changing its structure. It can lead to mutations and DNA damage.

BER involves several enzymes that work together to repair the damaged base. They include DNA glycosylase, AP endonuclease, DNA polymerase, and DNA ligase.

BER removes single damaged bases, while Nucleotide Excision Repair (NER) removes larger damaged segments of DNA involving multiple bases.

A DNA repair mechanism that removes damaged DNA segments, especially those caused by UV radiation, by cutting out the damaged portion and replacing it with a correct sequence.

Abnormal DNA structures formed when two adjacent pyrimidine bases (thymine, cytosine) bond together, often caused by UV radiation. They can hinder DNA replication and transcription.

A rare genetic disorder caused by mutations in genes involved in Nucleotide Excision Repair (NER), leading to an inability to repair DNA damage caused by UV radiation. This increases the risk of skin cancer.

Unrepaired pyrimidine dimers can hinder DNA replication and transcription. They can lead to mutations and, ultimately, cancer.

NER involves several steps: 1. Recognition of the damaged DNA segment. 2. Excision of the damaged segment. 3. Synthesis of a new, correct segment. 4. Ligation of the new segment into the DNA.