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(biochemistry) purine base found in DNA and RNA

Amino Acid

organic compounds containing an amino group and a carboxylic acid group


any chromosome that is not a sex chromosome


a specialized condensed region of each chromosome that appears during mitosis where the chromatids are held together to form an X shape


one of two identical strands into which a chromosome splits during mitosis


the readily stainable substance of a cell nucleus consisting of DNA and RNA and various proteins


a threadlike body in the cell nucleus that carries the genes in a linear order


One of the four aromatic bases found in DNA and RNA. Cytosine is a pyrimidine; it pairs with guanine.

Deoxyribose Sugar

Pentose sugar in Nucleotide


deoxyribonucleic acid, the material that contains the information that determines inherited characteristics


a mature sexual reproductive cell having a single set of unpaired chromosomes

Genetic Code

the ordering of nucleotides in DNA molecules that carries the genetic information in living cells


the complete genetic material contained in an individual


One of the four aromatic bases found in DNA and RNA. Guanine is a purine; it pairs with cytosine.


protein molecule around which DNA is tightly coiled in chromatin


term used to refer to chromosomes that each have a corresponding chromosome from the opposite-sex parent


cell division that produces reproductive cells in sexually reproducing organisms


cell division in which the nucleus divides into nuclei containing the same number of chromosomes

Nucleic Acid

an organic compound, either RNA or DNA, whose molecules are made up of one or two chains of nucleotides and carry genetic information

Polypeptide Chain

A chain of amino acids linked together by peptide bonds.

Ribose Sugar

sugar used in RNA to make up the "backbone"


ribonucleic acid, a natural polymer that is present in all living cells and that plays a role in protein synthesis

Sex Chromosome

one of two chromosomes of the 23rd pair of human chromosomes, which determine an individual's gender


of the body


nitrogen base found ONLY in DNA that pairs with adenine


The RNA version of thymine. Like thymine, this base also pairs with adenine.


fertilized egg


the stage of meiosis or mitosis when chromosomes move toward opposite ends of the nuclear spindle

Anti Codon

group of three bases on a tRNA molecule that are complementary to an mRNA codon

Coding Strand

RNA binds to this strand of DNA & copies it


three-nucleotide sequence on messenger RNA that codes for a single amino acid

Complimentary Base Pairs

the sequence of the strand on one strand determinesthe sequence of bases on the other strand


division of the cytoplasm during cell division

Degenerate Code

a genetic code in which some amino acids may be encoded by more than one codon each.

Disulphide Bridge

The S-S linkage, i.e. between two sulfur atoms, that forms during the cross-linking of amino acids during protein synthesis.

DNA Ligase

an enzyme that eventually joins the sugar-phosphate backbones of the Okazaki fragments

DNA Polymerase

enzyme involved in DNA replication that joins individual nucleotides to produce a DNA molecule


A cell characterized by the presence of a nucleus and other membrane-bound organelles. Eukaryotes can be unicellular (protists) or multicellular (fungi, plants and animals).


expressed sequence of DNA; codes for a protein


an enzyme that untwists the double helix at the replication forks, separating the two parental strands and making them available as template strands


an agent capable of activating specific genes


a period between two mitotic or meiotic divisions during which the cell grows, copies its DNA, and synthesizes proteins


sequence of DNA that is not involved in coding for a protein


photograph of chromosomes grouped in order in pairs

Lagging Strand

The strand in replication that is copied 3' to 5' as Okazaki fragments and then joined up.

Leading Strand

the new continuous complementary DNA strand synthesized along the template strand in the mandatory 5' --> 3' direction

Metabolic Pathways

Series of progressive chemical reaction steps involving energy production or conversion.


The chromosomes move to the center of the cell.


messenger RNA; type of RNA that carries instructions from DNA in the nucleus to the ribosome

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.

Operator Site

The site that a repressor protein can bind to to prevent transcription


a group of genes that operate together


having cells that lack membrane-bound nuclei

Promoter Site

part of DNA molecule that indicates where the sequence of base pairs that make up a gene begin


the first stage of mitosis or meiosis in eukaryotic cell division, during which the nuclear envelope breaks down and strands of chromatin form into chromosomes

Protein Synthesis

the formation of proteins by using information contained in DNA and carried by mRNA


nitrogeneous bases that have a double ring of carbon and nitrogen atoms such as adenine and guanine


nitrogenous bases that have a single ring of carbon and nitrogen atoms, such as cytosine and thymine

Regulator Gene

a genetic unit that regulates or suppresses the activity of one or more structural genes

Replication Fork

a Y-shaped point that results when the two strands of a DNA double helix separate so that the DNA molecule can be replicated

RNA Polymerase

An enzyme that links together the growing chain of ribonucleotides during transcription.

Structural Gene

a gene that codes for a product, such as an enzyme, protein, or RNA, rather than serving as a regulator


the final stage of meiosis when the chromosomes move toward opposite ends of the nuclear spindle

Template Strand

The DNA strand that provides the template for ordering the sequence of nucleotides in an RNA transcript.


(genetics) the organic process whereby the DNA sequence in a gene is copied into mRNA

Transcription Factor

A regulatory protein that binds to DNA and stimulates transcription of specific genes.

Transcription Unit

unit, a region of a DNA molecule that is transcribed into an RNA molecule


(genetics) the process whereby genetic information coded in messenger RNA directs the formation of a specific protein at a ribosome in the cytoplasm


The three nucleotides of DNA which code for one amino acid


transfer RNA; type of RNA that carries amino acids to the ribosome

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