BIO 340 - General Genetics: DNA Replication Flashcards

Flashcards about DNA Replication, covering topics such as DNA structure, replication mechanisms, key experiments, enzymes involved, and differences between prokaryotic and eukaryotic replication.

What is the significance of Watson and Crick's 1953 DNA model?

Proposed that DNA is a right-handed double helix with antiparallel strands and bases stacked on one another, connected by A-T and G-C base pairing, with 10 base pairs per helix turn.

What are the three components of a nucleotide, the building block of DNA?

1) a nitrogenous base, 2) a pentose sugar, and 3) a phosphate group.

Why is the width of the DNA molecule always the same?

The width of the DNA molecule remains constant because a pyrimidine always pairs with a purine.

How do A-T and G-C base pairings contribute to the structure of DNA?

A-T base pairs form two hydrogen bonds, and G-C base pairs form three hydrogen bonds, providing complementarity and stability.

What is the central dogma of molecular biology?

DNA -> RNA -> Protein

How has the definition of a gene evolved, especially after the ENCODE project?

Genes are now defined by their predicted sequence rather than the genetic loci responsible for phenotypes.

Why is the complementarity of DNA strands important for replication?

Each strand of DNA serves as a template for synthesizing the other strand.

What are the three proposed modes of DNA replication?

Conservative, semiconservative, and dispersive.

What did the Meselson and Stahl experiment demonstrate about DNA replication?

Demonstrated that DNA replication is semiconservative in prokaryotes, with each new molecule consisting of one old and one new strand.

How does DNA replication occur in bacteria?

Bacteria have a single circular DNA with replication originating at a single point (OriC), and replication is bidirectional, creating two replication forks.

What are the key requirements for DNA polymerase activity?

DNA template, four deoxyribonucleoside triphosphates (dNTPs), and a DNA or RNA primer.

In what direction does chain elongation occur during DNA synthesis?

Chain elongation occurs in the 5' to 3' direction.

Which DNA polymerases in bacteria have 3' to 5' exonuclease activity for proofreading?

DNA polymerases I, II, and III.

Which bacterial DNA polymerase is the holoenzyme primarily responsible for 5' to 3' polymerization in vivo?

DNA polymerase III

Which DNA polymerase(s) are the main DNA builder?

DNA polymerase II and III

What are the seven key issues that must be resolved during DNA replication?

Unwinding of the helix, reducing increased coiling, synthesizing an RNA primer, discontinuous synthesis of the lagging strand, removal of RNA primers, joining gap-filling DNA, and proofreading.

What roles do DnaA, DnaB, DnaC, and SSBPs play in unwinding the DNA helix in bacteria?

DnaA initiates unwinding at oriC, DnaB and DnaC further open and destabilize the helix, and single-stranded binding proteins (SSBPs) stabilize the open conformation.

Which enzymes remove positive supercoils ahead of the replication fork?

Topoisomerases

What is the role of primase in DNA replication?

Primase synthesizes an RNA primer to provide a free 3'-hydroxyl group for DNA polymerase III.

How do leading and lagging strand synthesis differ?

The leading strand is synthesized continuously, while the lagging strand is synthesized discontinuously as Okazaki fragments.

What is the function of DNA polymerase I and DNA ligase on the lagging strand?

DNA polymerase I removes primers on the lagging strand, and DNA ligase joins the fragments.

How does the presence of multiple origins of replication benefit eukaryotic DNA replication?

Eukaryotic chromosomes contain multiple origins of replication to allow the genome to be replicated in a matter of minutes to a few hours.

What are telomeres and what is their function?

Telomeres are long stretches of short repeating sequences at the ends of linear chromosomes that preserve chromosome integrity and stability.

Which enzyme maintains telomeres by adding small repeated segments of DNA to the ends of chromosomes?

Telomerase

What are the two major components of the telomerase enzyme?

Telomerase reverse transcriptase (TERT) and telomerase RNA (TR or TERC).