bio unit 6
Terms
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- leading strand
- The new continuous complementary DNA strand synthesized along the template strand in the mandatory 5' ( 3' direction.
- primer
- A polynucleotide with a free 3´ end, bound by complementary base pairing to the template strand, that is elongated during DNA replication.
- G2-phase
- The second growth phase of the cell cycle, consisting of the portion of interphase after DNA synthesis occurs.
- nuclear envelope
- The membrane in eukaryotes that encloses the nucleus, separating it from the cytoplasm.
- origin of replication
- Site where the replication of a DNA molecule begins
- DNA polymerase
- An enzyme that catalyzes the elongation of new DNA at a replication fork by the addition of nucleotides to the existing chain.
- cell cycle check point
- places in the cell cycle that are sensitive to either internal cell conditions or external chemical signals which must be "correct" for the cell to progress past them
- nucleic acid
- A polymer (polynucleotide) consisting of many nucleotide monomers; serves as a blueprint for proteins and, through the actions of proteins, for all cellular activities. The two types are DNA and RNA.
- purine
- One of two types of nitrogenous bases found in nucleotides. Adenine (A) and guanine (G) are purines.
- growth factor
- A protein that must be present in the extracellular environment (culture medium or animal body) for the growth and normal development of certain types of cells; a local regulator that acts on nearby cells to stimulate cell proliferation and differentiation.
- phosphodiester bond
- A phosphodiester bond is a group of strong covalent bonds between the phosphorus atom in a phosphate group and two other molecules over two ester bonds. Phosphodiester bonds are central to all life on Earth, as they make up the backbone of the strands of DNA.
- interphase
- The period in the cell cycle when the cell is not dividing. During interphase, cellular metabolic activity is high, chromosomes and organelles are duplicated, and cell size may increase. Interphase accounts for 90% of the cell cycle.
- cell cycle
- An ordered sequence of events in the life of a eukaryotic cell, from its origin in the division of a parent cell until its own division into two; composed of the M, G1, S, and G2 phases.
- pentose
- A pentose is a monosaccharide with five carbon atoms.
- Okazaki fragment
- A short segment of DNA synthesized on a template strand during DNA replication. Many Okazaki fragments make up the lagging strand of newly synthesized DNA.
- DNA ligase
- A linking enzyme essential for DNA replication; catalyzes the covalent bonding of the 3' end of a new DNA fragment to the 5' end of a growing chain.
- nucleolus
- A specialized structure in the nucleus, formed from various chromosomes and active in the synthesis of ribosomes.
- telomerase
- An enzyme that catalyzes the lengthening of telomeres. The enzyme includes a molecule of RNA that serves as a template for new telomere segments.
- centromere
- The centralized region joining two sister chromatids.
- topoisomerase
- A protein that functions in DNA replication, helping to relieve strain in the double helix ahead of the replication fork.
- cell plate
- A double membrane across the midline of a dividing plant cell, between which the new cell wall forms during cytokinesis.
- cytokinesis
- The division of the cytoplasm to form two separate daughter cells immediately after mitosis.
- pyrimidine
- One of two types of nitrogenous bases found in nucleotides. Cytosine (C), thymine (T), and uracil (U) are pyrimidines.
- bacteriophage
- A virus that infects bacteria; also called a phage.
- nucleosome
- The basic, bead-like unit of DNA packaging in eukaryotes, consisting of a segment of DNA wound around a protein core composed of two copies of each of four types of histone.
- G1-phase
- The first growth phase of the cell cycle, consisting of the portion of interphase before DNA synthesis begins.
- antiparallel
- The opposite arrangement of the sugar-phosphate backbones in a DNA double helix.
- chromosome
- A threadlike, gene-carrying structure found in the nucleus. Each chromosome consists of one very long DNA molecule and associated proteins. See chromatin.
- anaphase
- The fourth stage of mitosis, in which the chromatids of each chromosome have separated and the daughter chromosomes are moving to the poles of the cell.
- single-strand binding protein
- During DNA replication, molecules that line up along the unpaired DNA strands, holding them apart while the DNA strands serve as templates for the synthesis of complementary strands of DNA.
- telomere
- The protective structure at each end of a eukaryotic chromosome. Specifically, the tandemly repetitive DNA at the end of the chromosome's DNA molecule. See also repetitive DNA.
- replication
- DNA replication is the process of copying a double-stranded deoxyribonucleic acid (DNA) molecule, a process essential in all known life forms. The general mechanisms of DNA replication are different in prokaryotic and eukaryotic organisms.
- nitrogenous base
- Nitrogenous bases are organic compounds that owe their basic properties to the lone pair of electrons of a nitrogen atom. Typical nitrogenous bases are ammonia (NH3), triethylamine, pyridine, and the nucleobases adenine, guanine, thymine, cytosine, and uracil. Nitrogenous bases can be classified under two groups: purines (A and G) and pyrimidines (C, T, and U).
- primase
- An enzyme that joins RNA nucleotides to make the primer.
- helicase
- An enzyme that untwists the double helix of DNA at the replication forks.
- lagging strand
- A discontinuously synthesized DNA strand that elongates in a direction away from the replication fork.
- semiconservative replication
- Semiconservative replication describes the method by which DNA is replicated in all known cells. This method of replication was one of three proposed models[1] of DNA replication:
- S-phase
- The synthesis phase of the cell cycle; the portion of interphase during which DNA is replicated.
- telophase
- The fifth and final stage of mitosis, in which daughter nuclei are forming and cytokinesis has typically begun.
- cyclin
- A regulatory protein whose concentration fluctuates cyclically.
- replication fork
- A Y-shaped region on a replicating DNA molecule where new strands are growing.
- histone
- A small protein with a high proportion of positively charged amino acids that binds to the negatively charged DNA and plays a key role in its chromatin structure
- double helix
- The form of native DNA, referring to its two adjacent polynucleotide strands wound into a spiral shape.