Week 7 - Replication Flashcards
Replication Fork/Bubble
The Y-shaped structure that forms at the site where DNA is being unwound for replication. A replication bubble consists of two replication forks moving in opposite directions.
Origin of Replication
The specific sequence in the genome where DNA replication begins. Prokaryotes typically have a single origin, while eukaryotes have multiple origins.
Topoisomerase
An enzyme that helps relieve the strain on the DNA molecule ahead of the replication fork by cutting and rejoining the DNA strands to prevent supercoiling.
Helicase
An enzyme that unwinds and separates the two DNA strands at the replication fork by breaking hydrogen bonds between base pairs.
Template Strand
The original DNA strand that serves as a guide for the synthesis of a new complementary strand during replication.
Daughter Strand
The newly synthesized DNA strand that is complementary to the template strand.
Leading Strand Synthesis
The continuous synthesis of DNA in the 5’ to 3’ direction toward the replication fork, requiring only one primer.
Lagging Strand Synthesis
The discontinuous synthesis of DNA in the 5’ to 3’ direction away from the replication fork, forming short fragments (Okazaki fragments) that are later joined together.
Phosphodiester Bond
The covalent bond that connects nucleotides in the sugar-phosphate backbone of DNA, linking the 3’ hydroxyl group of one nucleotide to the 5’ phosphate of the next.
Base
The nitrogenous component of a nucleotide that participates in base pairing (adenine, thymine, cytosine, guanine, and in RNA, uracil).
Sugar Backbone
The structural framework of DNA and RNA, consisting of a chain of sugar (deoxyribose in DNA, ribose in RNA) molecules linked by phosphate groups.
Telomerase
An enzyme that extends the telomeres (ends of linear chromosomes) in eukaryotic cells to prevent the loss of genetic material during replication.
Reverse Transcriptase
An enzyme that synthesizes DNA from an RNA template, used by retroviruses (e.g., HIV) and in certain cellular processes like telomere maintenance.
Primer
A short RNA sequence that provides a starting point for DNA polymerase to begin DNA synthesis.
Primase
An enzyme that synthesizes RNA primers needed for DNA polymerase to initiate replication.
Ligase
An enzyme that seals nicks in the DNA sugar-phosphate backbone by forming phosphodiester bonds, particularly useful in joining Okazaki fragments.
3’-5’ Exonuclease
An enzyme activity that removes nucleotides in the 3’ to 5’ direction, often used for proofreading newly synthesized DNA.
Antiparallel
The orientation of the two DNA strands in opposite directions; one runs 5’ to 3’ while the other runs 3’ to 5’.
Semiconservative
The model of DNA replication in which each new DNA molecule consists of one original (parental) strand and one newly synthesized (daughter) strand.
5’-3’ Polymerase
The enzymatic activity of DNA polymerase that allows it to add nucleotides only in the 5’ to 3’ direction.
S-Phase
The phase of the cell cycle where DNA replication occurs, ensuring that each daughter cell receives an identical copy of the genome.
Major Groove
The larger of the two grooves in the DNA double helix, where proteins, like transcription factors, commonly bind to recognize specific DNA sequences.
Purine
A type of nitrogenous base with a two-ring structure; includes adenine (A) and guanine (G).
Pyrimidine
A type of nitrogenous base with a single-ring structure; includes cytosine (C), thymine (T) in DNA, and uracil (U) in RNA.
Base Pairing
The specific hydrogen bonding between complementary nitrogenous bases (A pairs with T, and C pairs with G in DNA; A pairs with U in RNA).
Proofreading
The ability of DNA polymerase to check and correct errors during DNA replication, usually using its 3’-5’ exonuclease activity.
