Module 7

Module 7—Molecular Genetics: DNA, RNA, and Protein Synthesis

Module Glossary

 

Consult the glossary in the textbook for other definitions that you may need to complete your work.

 

adaptive advantage: a difference in structure, physiology, or behaviour that gives an organism a better chance of survival

 

adenine (A): a nitrogenous base of the purine group; complementary base pairs with thymine

 

amino acid: an organic compound consisting of a carboxylic acid group, an amino group and other side groups linked together by peptide bonds to form proteins; the building blocks of proteins

 

anticodon: specialized base triplet located on one lobe of a transfer RNA molecule that recognizes its complementary codon on a messenger RNA (mRNA) molecule

 

antiparallel: describes the property by which the 5’ to 3’ phosphate bridges run in opposite directions on each strand of nucleotides in a double-stranded DNA molecule

 

anti-sense strand: strand of nucleotides from the double-stranded DNA molecule that is complementary to the sense strand and is not transcribed

 

bioremediation: use of living cells to perform environmental clean-up tasks, such as using bacteria to degrade PCBs into harmless compounds

 

Chargaff’s rule: in any sample of DNA, there is a constant relationship in which the amount of adenine is always approximately equal to the amount of thymine, and the amount of cytosine is always approximately equal to the amount of guanine

 

chemical mutagen: a molecule that can enter the cell nucleus and induce a permanent change in the genetic material of the cell by reacting chemically with DNA (e.g., nitrites)

 

chimera: a genetically engineered organism that contains DNA from unrelated species

 

chloroplast DNA (cpDNA): circular molecules of DNA found in the chloroplasts of plants; codes for the function of photosynthesis

 

chromosomal mutation: a mutation that involves the deletion, insertion, or crossing over of chromosomes

 

complementary base pairs: refers to the hydrogen-bonded, nitrogenous base pairs of adenosine and thymine, and of cytosine and guanine in the DNA double helix

 

codon: set of three bases that code for an amino acid or termination signal

 

cytosine (C): a nitrogenous base of the pyrimidine group; complementary base pairs with guanine

 

deletion: a type of point mutation where a nucleotide is removed from a DNA sequence, causing a frameshift mutation

 

deoxyribose sugar: a ring-shaped sugar; has one less oxygen than ribose sugar

 

DNA (deoxyribonucleic acid): a double-stranded nucleic acid molecule that governs the processes of heredity in the cells of all organisms

 

It is composed of nucleotides containing a phosphate group, a nitrogenous base, and deoxyribose.

 

DNA fingerprint: the pattern of bands into which DNA fragments sort during gel electrophoresis; this pattern is unique for every individual except twins and other multiple-birth people

 

DNA ligase: an enzyme that splices together Okazaki fragments during DNA replication of the lagging strand, or sticky ends that have been cut by a restriction endonuclease enzyme

 

DNA polymerase: an enzyme that slips into the space between two strands of DNA during replication to add DNA nucleotides in order to make complementary strands

 

DNA replication: the process of creating an exact copy of a molecule of DNA

 

double helix: spiral ladder shape of the DNA molecule, made up of two long strands of nucleotides bound together and twisted

 

elongation: the process of joining nucleotides to extend a new strand of DNA; relies on the action of DNA polymerase

 

endosymbiont theory: theory that eukaryotic cells developed by one species of prokaryote engulf another so that organelles are formed

 

frameshift mutation: permanent change in the genetic material of a cell caused by the insertion or deletion of one or two nucleotides, so that the entire reading frame of the gene is altered

 

gel electrophoresis: tool used to separate molecules according to their mass and charge; can be used to separate fragments of DNA

 

gene: a specific sequence of DNA that encodes a protein, tRNA, or rRNA, or that regulates the transcription of such a sequence

 

gene pool: the total of all the alleles of all genes in the individuals in a population

 

gene replacement therapy: the process of changing the function of genes to treat or prevent genetic disorders

 

genetic code: the order of base pairs in a DNA molecule

 

genetic engineering: manipulation of genetic material to alter genes and blend plant, animal and bacterial DNA

 

genome: the sum, or the entire DNA, carried in an organism’s cells

 

germ line mutation: mutation that occurs on a gamete and can be passed to the next generation

 

germ-line therapy: gene therapy used to modify the genetic information carried in egg and sperm cells

 

guanine (G): nitrogenous base of the purine group; complementary base pairs with cytosine

 

helicase: an enzyme that breaks segments of DNA during DNA replication; used in technologies to fragment DNA

 

Human Genome Project: joint effort of thousands of researchers from laboratories worldwide that determined the sequence of the three billion pairs of nucleotides making up the human genome

 

induced mutation: permanent change in genetic material caused by a mutagen outside the cell

 

insertion: a type of point mutation in which one nucleotide is added to the DNA sequence, causing a frameshift mutation

 

lactase: an enzyme involved in the digestion of lactose 

 

lagging strand: the strand that is replicated in short segments during DNA replication

 

leading strand: the strand that is replicated continuously in DNA replication

 

mitochondrial DNA (mtDNA): DNA within the mitochondria; is genetically identical to that of the female parent because the cytoplasm of offspring is derived from the egg (ovum)

 

mRNA (messenger RNA): strand of RNA that carries genetic information from DNA to the protein synthesis machinery of the cell during transcription

 

mutagen: substance or event that increases the rate of mutation in an organism

 

mutation: a permanent change in the genetic code (DNA) of a cell; a change in the sequence of bases on the DNA molecule

 

nitrogen base: an organic molecule containing nitrogen; two types present in DNA: double-ringed purines (adenine and guanine) and single-ringed pyrimidines (cytosine and thymine)

 

nucleotide: the repeating unit (monomer) of DNA; two strings of nucleotides joined in the middle by hydrogen bonds form a DNA molecule; each nucleotide is made up of a deoxyribose sugar, a nitrogenous base, and a phosphate group

 

Okazaki fragments: short nucleotide fragments synthesized during DNA replication of the lagging strand

 

phosphate: an inorganic phosphate group (PO43–)

 

physical mutagen: agent that can forcibly break a nucleotide sequence, causing random changes in one or both strands of a DNA molecule (e.g., X-rays)

 

plasmid: small self-duplication loop of DNA in a prokaryotic cell that is separate from the main chromosome and contains from one to a few genes

 

point mutation: permanent change in the genetic material of a cell that affects one or just a few nucleotides

 

primase: an enzyme in DNA replication that forms an RNA primer, which is used as a starting point for the elongation of nucleotide chains

 

promoter region: during transcription, a sequence of nucleotides on the DNA molecule that tells the RNA polymerase complex where to bind

 

protein: organic macromolecule assembled from subunits of amino acids

 

protein synthesis: amino acids forming larger protein molecules under the direction of DNA

 

recombinant DNA: a molecule of DNA that includes genetic material from different sources

 

replication bubble: oval-shaped, unwound area within a DNA molecule that is being replicated

 

replication fork: during DNA replication, Y-shaped points at which the DNA helix is unwound and new strands develop

 

replication origin: specific nucleotide sequence where replication begins

 

restriction endonuclease: type of restriction enzyme that recognizes a specific, short sequence of nucleotides within, rather than at the ends of, a strand of DNA, and then cuts the strand at that particular point within the sequence

 

restriction enzyme: an enzyme that cuts DNA at specific nucleotide sequences creating fragments

 

restriction fragment: a small segment of DNA cut from a DNA molecule by restriction endonucleases

 

restriction site: specific location within a short sequence of nucleotides in a strand of DNA where restriction endonucleases will cut

 

RNA: ribonucleic acid; a short, single strand composed of nucleotides with a nitrogen base, ribose sugar, and phosphate group; nitrogen bases include adenine, guanine, cytosine, and uracil; has a role in protein synthesis

 

RNA polymerase: main enzyme that catalyzes the formation of RNA from the DNA template

 

RNA primer: short strand of RNA that is complementary to a DNA template and serves as a starting point for the attachment of new DNA nucleotides

 

semi-conservative: term used to describe replication where each new molecule of DNA contains one strand of the original complementary DNA, and one new strand, conserving half of the original molecule

 

sense strand: the one strand of nucleotides from the double-stranded DNA molecule that is transcribed

 

somatic cell mutation: mutation that occurs in a body cell; passed on to daughter cells, but not to the next generation of individual organisms

 

somatic gene therapy: therapy that is aimed at correcting genetic disorders in somatic (body) cells

 

sticky end: short sequence of unpaired nucleotides remaining at each end of a restriction fragment on a single strand of DNA after an endonuclease makes a staggered cut at the restriction site

 

substitution: a type of point mutation in which one nucleotide is switched for another nucleotide in a DNA sequence

 

target sequence: in DNA replication, a short sequence of nucleotides within a strand of DNA recognized and cut by restriction endonucleases

 

termination: the completion of the new DNA strands and the dismantling of the replication machine

 

thymine (T): nitrogenous base of the pyrimidine group; complementary base pairs with adenine

 

transcription: a strand of messenger RNA (mRNA) is produced that is complementary to a segment of DNA

 

transgenic organism: produced by incorporating the DNA from one organism into another to create a new genetic combination

 

translation: second stage of gene expression, in which the mRNA nucleotide sequence directs the synthesis of a polypeptide with the aid of tRNA

 

tRNA (transfer RNA): type of RNA that works with messenger RNA (mRNA) to direct the synthesis of a polypeptide in a process known as translation

 

uracil (U): a nitrogenous base found only in RNA, not DNA; replaces thymine when paired to adenine

 

Watson and Crick: credited with co-discovery of the structure of DNA; received the Nobel Prize for their work

 

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