DNA Replication, Repair, Chromosome Structure, and Cellular Respiration

Vocabulary practice flashcards covering DNA replication enzymes, DNA repair pathways, chromosome structure and telomeres, and cellular energetics including redox reactions.

DNA helicase

An enzyme that binds near the origin of replication and unwinds double-stranded DNA into single-stranded DNA to produce the replication bubble.

Replication bubble

A region of single-stranded DNA surrounded by double-stranded DNA where DNA replication takes place.

Single-stranded binding proteins

Proteins that bind to single-stranded DNA within the replication bubble to stabilize it so replication can occur.

Primase

An enzyme that synthesizes a short single-stranded RNA primer and attaches it to single-stranded DNA.

RNA primer

A short segment of single-stranded RNA synthesized by primase that provides a binding site for DNA polymerase III.

DNA polymerase III

An enzyme that binds to an RNA primer on single-stranded DNA and synthesizes a new complementary strand in the 5' to 3' direction.

Okazaki fragments

Individual pieces or fragments of DNA synthesized on the lagging strand moving away from the replication fork.

DNA polymerase I

An enzyme that removes RNA primers and replaces the RNA bases with DNA nucleotides.

DNA ligase

An enzyme that connects Okazaki fragments on the lagging strand by forming phosphodiester bonds.

Topoisomerase

An enzyme that relieves supercoiling and super-twisting in DNA to prevent it from becoming wound too tightly for replication.

Trombone model

A proposed model of bacterial DNA replication where the replication proteins and enzymes form a structure resembling a trombone.

Proofreading activity

The mechanism by which DNA polymerase checks its work, removes an incorrect nucleotide, and replaces it with the correct base.

Mismatch repair

A repair pathway where repair enzymes other than DNA polymerases detect and correct mispaired bases that escaped proofreading.

Mutations

Permanent, random sequence changes within the DNA of a cell, caused by spontaneous events or physical and chemical agents.

Nucleotide excision repair

A repair process in which a nuclease cuts out damaged or incorrectly paired base pairs in a row, DNA polymerase fills the gap, and DNA ligase seals the strand.

Nuclease

An enzyme that cuts out and removes one or more incorrectly added or damaged base pairs in nucleotide excision repair.

Alleles

Different versions of genes whose frequencies in a population can be altered by environmental pressures via natural selection.

Natural selection

The process by which the environment causes certain alleles to become more or less common in a population.

Speciation

The creation of new species resulting from accumulated mutations and natural selection.

Telomeres

Repetitive DNA sequences at the ends of linear eukaryotic chromosomes that protect inner essential genes from being eroded during rounds of replication.

Telomerase

An enzyme present in germ cells and cancer cells that lengthens and extends telomeres by adding DNA bases to chromosome ends.

Cellular respiration

The process by which animal and plant cells break down organic molecules such as sugars to produce ATP.

Catabolic pathways

Metabolic pathways that break down complex molecules into simpler ones, releasing free energy to the surroundings.

Exergonic

A term describing chemical processes, such as the breakdown of organic molecules, that release free energy.

Fermentation

The partial breakdown of sugars to produce ATP occurring entirely in the absence of oxygen ($O_2$).

Aerobic respiration

A form of cellular respiration that breaks down organic molecules in the presence of oxygen ($O_2$) to produce ATP.

Anaerobic respiration

A form of cellular respiration that functions in the absence of oxygen ($O_2$) and transfers electrons to an atom or molecule other than oxygen to produce ATP.

Redox reactions

Oxidation-reduction chemical reactions in which one substance loses electrons while another substance gains electrons.

Oxidation

The loss of one or more electrons from a substance during a chemical reaction.

Reduction

The gain of one or more electrons by a substance, which reduces or makes its positive charge more negative.

Reducing agent

A substance that donates electrons to an electron acceptor in a redox reaction, thereby becoming oxidized.

Oxidizing agent

A substance that takes or removes electrons from an electron donor in a redox reaction, thereby becoming reduced.