Introns
Non-coding fragments of DNA.
Exons
Protein-coding fragments of DNA.
Highly repetitive sequences
Sequences of DNA in the genome which acount for 5-45% of the total genome and are not used for coding purposes.
Structural DNA
Tightly coiled DNA which does not have a coding function, and occurs around the centromere of a chromosome.
Histone
Proteins structures paired with DNA in eukaryotic cells which package DNA.
Purines
Double-ring structured nitrogenous bases; adenine and guanine
Pyrimidines
Single-ring structured nitrogenous bases; cytosine and thymine
Semiconservative Model of DNA Replication
A model of DNA replication that shows how complimentary base pairs act as a template to allow for the copying of the strand of DNA.
Leading Strand
the new continuous complementary DNA strand synthesized along the template strand in the mandatory 5' --> 3' direction
Lagging Strand
A discontinuously synthesized DNA strand that elongates in a direction away from the replication fork, because the strand runs in the 3' -->5' direction, requiring elongation to occur as Okazaki fragments which are later joined my DNA ligase.
DNA Ligase
An enzyme that eventually joins the sugar-phosphate backbones of the Okazaki fragments.
DNA Polymerase I
Enzyme which removes RNA primers and replaces them with the appropriate nucleotides during DNA replication.
DNA Polymerase III
Enzyme which is responsible for synthesizing complementary strands of DNA during DNA replication.
RNA Primer
Short segment of RNA used to initiate synthesis of a new strand of DNA during replication
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.
Primase
An enzyme that joins RNA nucleotides to make the primer using the parental DNA strand as a template.
Helicase
An enzyme that untwists the double helix at the replication forks, separating the two parental strands and making them available as template strands during DNA replication
Transcription
The process by which a DNA sequence in a gene is copied into mRNA to be transported out of the nucleus and to the site of the ribosome for protein synthesis.
Terminator
A sequence of nucleotides that, when transcribed, causes the RNA polymerase to detach from the DNA, stopping the transcription process, and releasing the RNA transcript from the DNA strand.
A Site
Site on the ribosome which holds the tRNA carrying the next amino acid to be added to the polypeptide chain.
P Site
Site on the ribosome which holds the tRNA carrying the growing polypeptide chain.
E Site
Site on the ribosome from which tRNA that has lost its amino acid is discharged.
Translation
The process of translating genetic information coded for in messenger RNA to synthesize a specific protein at a ribosome in the cytoplasm.
Initiation Phase
Phase of translation in which a the start codon AUG begins the process of translation, and appropriate amino acids are attached to their corresponding tRNA anticodons.
Elongation Phase
Phase of translation in which involves tRNA bringing amino acids to the mRNA-ribosomal complex in the order specified by the codons of the mRNA.
Translocation Phase
Phase of translation which occurs during the elongation phase, involving the movement of the tRNAs from one ribosomal site to the next.
Termination Phase
Phase of translation in which the three stop codons appear at the A-site of the ribosome, and a protein called the release factor (which has no attached amino acid) fills the A-site. This catalyses the the hydrolysis of the bond btween the tRNA and the P-
Haemoglobin
Protein which contains iron that thransports oxygen from the lungs to all parts of the body in vertebrates.
Actin and Myosin
Proteins that interact to bring about muscle movement (contraction) in animals.
Insulin
A hormone secreted by the pancreas that aids in maintaining blood glucose level in vertebrates,
Immunoglobins
A group of proteins that act as antibodies to fight bacteria and viruses.
Amylase
A digestive enzyme that catalyses the hydrolysis of starch.
Primary Organzation
The protein structure in which the unique sequence of amino acids is held together by peptide bonds in each protein.
Secondary Organzation
The protein structure in which hydrogen bonds are formed between the oxygen from one carboxyl group of one amino acid and the hydrogen from the amino group of another. The two most common confugurations of this structure are the alpha-helix and the beta-p
Tertiary Organzation
The protein structure in whichthe polypeptide chain bends and folds over itself because of the interactions among R-groups and the peptide backbone, resulting in a definate three-dimensional conformation.
Quaternary Organzation
The protein structure which involves multiple polypeptide chains which combine to form a single structure. All bonds found in the other three levels of organization are present in this structure.
Fibrous Proteins
Proteins composed of many polypeptide chains in a long, narrow shape, usually insoluble in water, such as collagen and actin.
Globular Proteins
Proteins which are more three dimensional in their shape and are mostly water soluble, such as haemoglobin and insulin.
Polar Amino Acids
Amino acids which have hydrophyllic properties and are found in regions of proteins which are exposed to water, such as membrane proteins. These amino acids create hydrophyllic channels through which polar substances can move.
Non-Polar Amino Acids
Animo acids which are hydrophobic, found in the regions of proteins that are linked to the hydrophobic area of the cell membrane.
Anabolic Rections
Reactions which build complex molecules, are endergonic, and are biosynthetic, such as photosynthesis.
Catabolic Reactions
Reactions which break down complex molecules, are exergonic, and are degradative, such as cellular respiration.
Activation Energy
Energy which is necessary to destablize the existing chemical bonds in the substrate of an enzyme-catalysed reaction.
Competitive Inhibition
Type of inhibition where an inhibitor competes directly for the site of an enzyme so that the substrate may not come in contact with the active site and the chemical reaction rate is decreased.
Non-Competitive Inhibition
Type of inhibition where an allosteric inhibtor interacts with the enzyme to change the shape of the actice site, but does not compete directly for the active site.
End-Product Inhibition
Type of inhibtion which prevents the cell from wasting resources by making more substance than is needed. When the end product is present in sufficient quantity, the action of the first enzyme is inhibited by the end product which acts as an allosteric in