Glossary
Acrocentric:- Acrocentric chromosomes have centromeres very close to one end, giving the chromosome a "V" shaped appearance. The short (p) arms are very short and usually have small dot-like appendages on stalks: satellites. The acrocentric human chromosomes are 13,14,15,21 & 22.
ACUS/LSIL:- Atypical squamous celles of uncertain significance/low-grade squamous intraepithelial lesion.
Adenine (A):-- A base; one of the molecular components of DNA and RNA. Bonds with thymine (A-T) in DNA and with uracil (A-U) in RNA.
Alleles:-- Alternative forms of a genetic locus; a single allele for each locus is inherited separately from each parent (e.g., at a locus for eye color the allele might result in blue or brown eyes).
Amino acid:- Any of a class of over 20 molecules that are combined to form proteins in living things. The sequence of amino acids in a protein and hence protein function are determined by the genetic code.
Amplification:- An increase in the number of copies of a specific DNA fragment; can be in vivo or in vitro. See Cloning, Polymerase chain reaction.
Apoptosis:- programed cell death
Arrayed library: Individual primary recombinant clones (hosted in phage, cosmid, YAC or other vector) that are placed in 2-dimensional arrays in microtiter dishes. Each primary clone can be identified by the identity of the plate, and the clone location (row = file and column like X, Y), used possibly for screening as well as for physical mapping. Genetic linkage and physical map analyses is entered into a relational database used to construct physical and genetic linkage maps. Compare Library, Genomic library.
ATM:- Ataxia-telangiectasia gene.
Autoradiography:- Uses Xray film to visualize radioactively labeled molecules or fragments of molecules. Used in analyzing length and number of DNA fragments after they are separated by gel electrophoresis.
Autosome:- A chromosome not involved in sex determination
Bacteriophage:- See phage.
Base pair (bp):- Two nitrogenous bases (adenine and thymine or guanine and cytosine) held together by weak bonds. Two strands of DNA are held together as a double helix by the bonds between base pairs. Adenine always bonds with thymine (A-T), and cytosine always bonds with guanine (C-G).
Base sequence:- The order of bases--nucleotides--in a DNA molecule.
Bases:- The molecular building blocks of DNA and RNA: adenine, cytosine, guanine, thymine, and (in RNA only) uracil. In DNA, A attaches only to T, and C attaches only to G. In RNA, A attaches only to U. C attaches only to G.
B-cells (B lymphocytes):- – White blood cells that mature in the bone marrow
Biotechnology:- A set of biological techniques developed through basic research and now applied to research and product development. The use by industry of recombinant DNA, cell fusion and new bioprocessing techniques to manufacture products.
Biparental:- Involving or inherited from both parents
Bouquet formation:- Telemere and also centromere clustering on the nuclear envelope or nucleolus for prealignment of homologues.
bp:- Base pair.
Carcinoma:- Tumor of epithelial cells.
cDNA:- See complementary DNA.
Cell-mediated immunity (cellular immunity):- – Immune protection provided by the direct action of immune cells, including cytotoxic T-cells.
Cells:- The basic units of life. All living organisms are a collection of cells.
Centimorgan (cM):- A unit of measure of recombination frequency. One centimorgan is equal to a 1% chance that a marker at one genetic locus will be separated from a marker at a second locus due to crossing over in a single generation. In human beings, 1 centimorgan is equivalent, on average, to 1 million base pairs.
cM:- Centimorgan.
Centromere:- The constricted or pinched in part of the chromosome separating the short (p) arm from the long (q) arm. It is the attachment point for the mitotic spindle during cell division. Has 2 centrioles
Centromeric fission:- Splitting of the chromosome horizontally through the centromere, separating the p and q arms.
Chimera:- Mosaicism in which an individual or tissue contains a mix of cells derived from 2 genetically different individuals. The blood of a patient who had a transfusion from another individual would be chimeric.
Chromosomes: The selfreplicating genetic structures of cells containing the cellular DNA that bears in its nucleotide sequence the linear array of genes. In prokaryotes, chromosomal DNA is circular and the entire genome is carried on one chromosome. Eukaryotic genomes consist of a number of chromosomes whose DNA is associated with different kinds of proteins.
Clone bank: See genomic library.
Clone:- A group of genetically identical cells or o rganisms that are descended from one parent. Identical twins are clones, as are colonies of bacteria that reproduce by simple cell division.
Cloning vector:- DNA molecule originating from a virus, a plasmid, or the cell of a higher organism into which another DNA fragment of appropriate size can be integrated without loss of the vectors capacity for self- replication; vectors introduce foreign DNA into host cells, where it can be reproduced in large quantities. Examples are plasmids, cosmids, and yeast artificial chromosomes; vectors are often recombinant molecules containing DNA sequences from several sources.
Cloning:- The process of asexually producing a group of cells (clones), all genetically identical, from a single ancestor.
cM:- See centimorgan.
Code:- See genetic code.
Complementary DNA (cDNA):- DNA that is synthesized from a messenger RNA template; the single-stranded form is often used as a probe in physical mapping. The complementary sequence to G-T-A-C is C-A-T-G.
Complementary sequences:- Nucleic acid base sequences that can form a double- stranded structure by matching base pairs; the complementary sequence to G- T- A- C is C- A- T- G.
Conserved sequence:- A base sequence in a DNA molecule (or an amino acid sequence in a protein) that has remained rather unchanged throughout evolution.
Contig map:-- A map depicting the relative order of a linked library of small overlapping clones representing a complete chromosomal segment.
Contigs:- Groups of clones representing overlapping regions of a genome.
Cosmid: Artificially constructed cloning vector containing the cos gene of phage lambda. Cosmids can be packaged in lambda phage particles for infection into E. coli; this permits cloning of larger DNA fragments (up to 45 kb) than can be introduced into bacterial hosts in plasmid vectors.
Crossingover:- The breaking during meiosis of one maternal and one paternal chromosome, the exchange of corresponding sections of DNA, and the rejoining of the chromosomes at their chiasmata (bridges). This can result in an exchange of alleles between chromosomes. Compare recombination.
Cytosine (C):- A nitrogenous base, one member of the base pair G- C (guanine and cytosine).
Cytotoxic T-cells (CD8+ T-cells, killer T-cells, cytotoxic lymphocytes, CTLs): – Lymphocytes--white blood cells maturing in the thymus gland--that destroy infected or damaged cells.
DAPI:- blue fluorescent dye "perfect" for DNA: 4'6-diamidino-2-phenylindole.
Deletion:- Loss of a whole chromosome or part of a chromosome. Usually refers to loss by partial deletion. A terminal deletion occurs at the end of a chromosome. Interstitial deletion is loss between the ends.
Dendritic cells: – White blood cells found in the spleen and other lymphoid organs that contain antigens and present them to T-cells.
Diploid:- A full set of genetic material, consisting of paired chromosomes, one chromosome from each parental set. Most animal cells except the gametes have a diploid set of chromosomes. The diploid human genome has 46 chromosomes. Compare haploid.
Diploidy:- A cell with a normal chromosome number including 2 sets of parental chromosomes. See triploidy and tetraploidy.
Disomy:- Meaning 2 bodies. Refers to a normal chromosome pair.
DNA (deoxyribonucleic acid):- The molecule that encodes genetic information. DNA is a double- stranded molecule held together by weak bonds between base pairs of nucleotides. The 4 nucleotides in DNA contain the bases: adenine (A), guanine (G), cytosine (C), and thymine (T). In nature, base pairs form only between A and T and between G and C; thus the base sequence of each single strand can be deduced from that of its partner.
DNA fingerprinting:- Uses fragments of DNA to identify the unique genetic makeup of an individual.
DNA probes:- See probe.
DNA replication:- The use of existing DNA as a template for the synthesis of new DNA strands. In humans and other eukaryotes, replication occurs in the cell nucleus.
DNA sequencing:- Determining the order of bases in a segment of DNA.
Domain:-A discrete portion of a protein with its own function. The combination of domains in a single protein determines its overall function.
Dominant gene:- A gene which, when present on a chromosome, passes on a certain physical characteristic, thereby dominating over a recessive gene present on the same or another chromosome.
Double helix:- A common name for DNA It has adouble-stranded, spiraling structure.
DTH:-- Delayed type hypersensitivity
Duplication:- A double copy of part of a chromosome resulting in an extra (abnormal) dose of the duplicated material.
E. coli, Escherichia coli:- Common bacterium intensively studied because of its small genome size, normal lack of pathogenicity and ease of growth.
Electrophoresis:- A method of separating large molecules such proteins from a mixture of similar molecules. An electric current is passed through agarose or acrylamide gels containing the mixture. Each kind of molecule travels through the medium at a different rate, depending on its electrical charge and size. are the media commonly used for electrophoresis of proteins and nucleic acids.
Endonuclease restriction enzyme:- A protein that recognizes specific, short sequences of DNA and cuts at those sites it is restricted to. See also Restriction enzyme cutting site.
Enzyme:- A proteinaceous catalyst, speeding or slowing the rate at which a biochemi cal reaction proceeds.
Escherichia coli, E. coli:- Common bacterium intensively studied because of its small genome size, normal lack of pathogenicity, and ease of growth.
EST:- Expressed sequence tag. See Sequence tagged site.
Euchromatin:- Chromosomal DNA which is genetically active and pale staining with G-, Q- and C- banding. Euchromatin is relatively rich in GC base pairs. During interphase it is uncoiled and transcriptionally active whereas heterochromatin is condensed and inactive.
Eukaryote:- Cell or organism with membrane-bound, structurally discrete nucleus and other well- developed subcellular compartments. Eukaryotes include all organisms except viruses, bacteria and bluegreen algae. Compare prokaryote. See chromosomes.
Evolutionarily conserved:- See conserved sequence.
Exogenous DNA:- DNA originating outside an organism.
Exons:- The protein- coding DNA sequences of a gene. Compare introns.
Exonuclease:- An enzyme that cleaves nucleotides sequentially from free ends of a linear nucleic acid substrate.
FISH:- Fluorescence In-Situ Hybridisation. The technique whereby small lengths of DNA (probes) which recognise complementary DNA on particular chromosomes are labelled with a colored fluorescent dyes then used to highlight target DNA in chromosomes.
Flow cytometry:- Analysis of biological material by detection of the light- absorbense or fluorescense of cells or subcellular fractions (i.e., chromosomes) passing in a narrow stream through a laser beam. A profile of the sample is produced. Automated sorting devices, used to fractionate samples, sort successive droplets of the stream into different fractions.
Flow karyotyping:- Use of flow cytometry to analyze or separate chromosomes on the basis of their DNA content.
Fragile Site:- A small break or constriction in a chromosome that can be visualised after special treatment of the chromosomes. Fragile X syndrome, a fragile site often seen on the X chromosome.
Gamete:- The germ cell (sperm or ovum) containing a single set of chromosomes from one parent each a haploid set of chromosomes (23 for humans), but has a double set to be reduced after fertilization when the organism is haploid, a haplont.
G-bands:- Giemsa stain banding patterns on chromosomes make it easier to examine the chromosomes for abnormalities in structure and number..
Gel:- A dense net work of fine particles dispersed with water (Gelatin is a gel). Used to separate different-sized strands of DNA.
Gene cloning:- Isolating a gene and then making multiple copies of it by inserting it into a bacterial cell or another organism.
Gene expression:- The process by which a genes coded information is converted into the structures present and operating in the cell. Expressed genes include those that are transcribed into mRNA and then translated into protein and those that are transcribed into RNA but not translated into protein (e.g., transfer and ribosomal RNAs).
Gene families:- Groups of closely related genes that make similar products.
Gene library: See Genomic library.
Gene mapping:- Determination of the relative positions of genes on a DNA molecule (chromosome or plasmid) and of the distance, in linkage units or physical units, between them.
Gene product:-The biochemical material, either RNA or protein, resulting from expression of a gene. The amount of gene product is used to measure how active a gene is; abnormal amounts can be correlated with disease- causing alleles.
Gene therapy:- A method of treating genetic conditions by inserting a correct copy of the gene in question into the cells of individuals who have a mutated gene.
Gene:- The basic unit of heredity. A sequence of DNA nucleotides within a chromosome with genetic code information which is responsible for a particular bodily function or characteristic.
Genetic code:- The sequence of nucleotides, coded in triplets (codons) along the mRNA that determines the sequence of amino acids in protein synthesis. The DNA sequence of a gene can be used to predict the mRNA sequence. The genetic code can in turn be used to predict the amino acid sequence.
Genetic engineering technologies:--See Recombinant DNA technologies.
Genetic engineering:- The technology used to genetically manipulate living cells to produce new chemicals or to perform new functions.
Genetic map: See Linkage map.
Genetic material: See Genome.
Genetic testing (o r genetic screening):- A search for a certain gene.
Genetics:- The study of the patterns of inheritance of specific traits. The study of characteristics which are passed on (inherited) through successive generations in humans and other organisms due to the transmission of genetic material (DNA).
Genome projects: Research and technology development efforts aimed at mapping and sequencing some or all of the genome of human beings and other organisms.
Genome:- All the genetic material in the chromosomes of a particular organism. The human genome consists of 3 billion bases, organized in 100,000 genes on 23 chromosomes.
Genomic library:- A collection of clones made from a set of randomly generated overlapping DNA fragments representing the entire genome of an organism. Compare library, arrayed library.
Genotype:- The entire genetic identity of an individual, including alleles that do not show as outward characters.
Guanine (G):- A nitrogenous base, one member of the base pair G- C (guanine and cytosine).
HAI- Hemagglutination inhibition.
Haploid:- A single set of chromosomes (half the set of diplonts), present in the egg and sperm cells of animals, and in the egg, pollen cells of plants and the single cells of many Protista. Compare diploid.
Heterochromatin:- Chromosomal material which is condensed and genetically inactive during interphase. It consists of repetitive DNA sequences which are relatively rich in AT base pairs and is late replicating in the cell cycle. In metaphase chromosomes it is dark staining with G- and C- banding.
Heterozygosity:- The presence of different alleles at one or more loci on homologous chromosomes.
Homeobox:- A short stretch of nucleotides whose base sequence is virtually identical in all the genes that contain it. It has been found in many organisms from fruit flies to human beings. In Drosophila, a homeobox determines when particular groups of genes are expressed during development.
Homolog searching:- Sister chromatids seek each other for crossovers.
Homologies:- Similarities in DNA or protein sequences between individuals of the same species or among different species.
Homologous chromosomes (homologs):- A pair of chromosomes containing the same linear gene sequences, each derived from one parent.
Homozygote:- Refers to an individual in whom the 2 alleles or gene copies contain identical information.
Hormone:- A chemical product of the body that has a specific regulatory effect upon the cells.
Human gene therapy:- Insertion of normal DNA directly into cells to correct a genetic defect.
Human Genome Initiative:- Collective name for several projects begun in 1986 by DOE to 1/ create an ordered set of DNA segments from known chromosomal locations, 2/ develop new computational methods for analyzing genetic map and DNA sequence data, and 3/ develop new techniques and instruments for detecting and analyzing DNA.
Human Genome Project (HGP):-.A worldwide project aimed at deciphering all the 3 billion bases of the human genome, including mapping and sequencing every gene.
HGP:- Human Genome Project.
Hybridization:- The process of joining 2 complementary strands of DNA or one each of DNA and RNA to form a double- stranded molecule.
Immortal- Applied to cells like HeLa (donor Helan Lane, 1950s, cervical cancer) that propogate forever like a typical cancer cell, whereas normal cells die out after say 50 generations in vitro.
Imprinting:- The "memory" held by a chromosome as to which parent it was inherited from. The memory is chemically "stamped" into the DNA and can result in chromosomes behaving differently, depending on the parent of origin.
In situ hybridization:- Use of a DNA or RNA probe to detect the presence of the complementary DNA sequence in cloned bacterial or cultured eukaryotic cells.
In vitro:- Outside a living organism as growing on glass in tissue or cell culture.
In vivo:- Inside a living organism. Simply alive.
Informatics:- The study of the application of computer and statistical techniques to the management of information. In genome projects, informatics includes the development of methods to search databases quickly, to analyze DNA sequence information and other diverse information, and to predict protein sequences and structures from DNA sequence data.
Interstitial:- Any part of a chromosome between the ends (telomeres).
Introns:- The DNA base sequences interrupting the protein- coding sequences of a gene; these sequences are transcribed into RNA but are cut out of the message before it is translated into protein. Compare exons.
Inversion:- Breakage of a chromosome in 2 places followed by a 180 degree switch of the segment between the breaks. The sequence of the inverted segment is reversed.
ISCN:- The International System of Cytogenetic Nomenclature.
Isochromosome:- A metacentric chromosome in which the p and q arms are of equal length and the information in each arm is genetically identical.
Karyotype:- A photomicrograph of an individuals chromosomes arranged in a standard format showing the number, size, and shape of each chromosome type; used in low- resolution physical mapping to correlate gross chromosomal abnormalities with the characteristics of specific diseases.
kb:- See Kilobase.
Kilobase (kb):- Unit of length for DNA fragments equal to 1000 nucleotides.
Kinetochore:-Attachment of the centromere.
Koilocytes- Epidermal cells in the superficial layers of the epidermis that have a swollen, glassy, highly eosinophilic cytoplasm. They likely contain papillomavirus.
Library:- An unordered collection of clones (i.e., cloned DNA from a particular organism), whose relationship to each other can be established by physical mapping. Compare Genomic library, Arrayed library.
Linkage map:- A map of the relative positions of genetic loci on a chromosome, determined on the basis of how often the loci are inherited together. Distance is measured in centimorgans (cM).
Linkage:- The proximity of 2 or more markers (e.g., genes, RFLP markers) on a chromosome; the closer together the markers are, the lower the probability that they will be separated during DNA repair or replication processes (mitosis in prokaryotes, mitosis or meiosis in eukaryotes), and hence the greater the probability that they will be inherited together.
Localize:- Determination of the original position (locus) of a gene or other marker on a chromosome.
Locus (pl. loci):- The position on a chromosome of a gene or other chromosome marker; also, the DNA at that position. The use of locus is sometimes restricted to mean regions of DNA that are expressed. See Gene expression.
LSIL:- Low-grade squamous intraepithelial lesion.
Macrorestriction map:- Map depicting the order of and distance between sites at which restriction enzymes cleave chromosomes.
Mapping:- See gene mapping, physical map.
Mapping:- See gene mapping, linkage map, physical map.
Marker:- An identifiable physical location on a chromosome (e.g., restriction enzyme cutting site, gene) whose inheritance can be monitored. Markers can be expressed regions of DNA (genes) or some segment of DNA with no known coding function but whose pattern of inheritance can be determined. See RFLP, restriction fragment length polymorphism.
Mb:- See megabase.
Megabase (Mb):- Unit of length for DNA fragments equal to 1 million nucleotides and roughly equal to 1 cM.
Meiosis:- A series of cell divisions that contain a reduction division before--gametic--or after--zygotic--fertilization. Gametic meiosis results in 4 rather than 2 daughter cells, each with a haploid set of chromosomes. Compare to mitosis.
Messenger RNA (mRNA):- A single-stranded molecule of ribonucleic acid that serves as a template for protein synthesis.
Metacentric:- A metacentric chromosome has its centromere in the middle and the p and q arms are of equal length.
Metaphase:- A stage in mitosis or meiosis during which the chromosomes are aligned along the equatorial plane of the cell.
Interphase:- A stage in mitosis or meiosis during which the chromosomes are diffuse. The resting state between the other stages.
Mitosis:- The process of nuclear division in cells that produces daughter cells that are genetically identical to each other and to the parent cell.
Modal number:- The chromosome count which is most frequent.
Monosomy:- A single copy of a chromosome rather than a pair (disomy).
Mosaicism:- The co-existence of genetically different cells within the same individual or tissue. e.g. a mixture of both normal cells and cells with a chromosome abnormality.
mRNA:- See messenger RNA.
Multifactorial or multigenic disorders:- Polygenic disorders.
Multiplexing:- A sequencing approach that uses several pooled samples simultaneously, greatly increasing sequencing speed.
Mutation:- A spontaneous or induced heritable change in the DNA of a cell.
Nitrogenous base:- A nitrogen- containing base.
Nondisjunction:- The failure of homologs to segregate into each daughter cell during mitotic or meiotic anaphase. Both sister chromosomes go to the same daughter cell, resulting in a deficit in one cell and an excess in the other.
Nucleic acid:- A large molecule composed of nucleotide subunits.
Nucleotide:- A molecular subunit of DNA or RNA consisti ng of a base (adenine, guanine, thymine or cytosine in DNA; adenine, guanine, uracil, or cytosine in RNA). Thousands of nucleotides are linked to form a DNA or RNA molecule. See DNA, base pair, RNA.
Nucleus:- The cellular organelle in eukaryotes that contains the genetic material.
-oma- Tumor of . . .
Oncogene:- A gene causing or associated with cancer, often associated with cellular rate of growth.
ORF- Open reading frame.
Overlapping clones:- See Genomic library.
PCR:- See Polymerase chain reaction.
Phage:- A virus for which the natural host is a bacterium.
Phenotype:- The outward physical characteristics of an organism.
Physical map:- A map of the locations of identifiable landmarks on DNA (restriction enzyme cutting sites, genes), regardless of inheritance. Distance is measured in base pairs.
Plasmid:- Autonomously replicating, extrachromosomal circular DNA molecules, distinct from the normal bacterial genome and nonessential for cell survival under nonselective conditions. Some plasmids are capable of integrating into the host genome. A number of artificially constructed plasmids are used as cloning vectors.
Polygenic disorders:- Genetic disorders resulting from the combined action of alleles of more than one gene (e.g., heart disease, diabetes, and some cancers). Although such disorders are inherited, they depend on the simultaneous presence of several alleles; thus the hereditary patterns are usually more complex than those of single- gene disorders. Compare single- gene disorders.
Polymerase chain reaction (PCR):- A "biological copy machine": a method for making many copies of a specific DNA base sequence. A method for amplifying a DNA base sequence using a heat-stable polymerase and 2 20- base primers, one complementary to the (+)- strand at one end of the sequence to be amplified and the other complementary to the (- )- strand
Polymerase, DNA or RNA:- Enzymes that catalyze the synthesis of nucleic acids on preexisting nucleic acid templates, assembling RNA from ribonucleotides or DNA from deoxyribonucleotides.
Polymerase:- An enzyme that acts like a molecular assembly line to build new strands of DNA something like a negative photo producing a positive..
Polymorphism:- Difference in DNA sequence among individuals. Genetic variations occurring in more than 1% of a population would be considered useful polymorphisms for genetic linkage analysis. Compare Mutation.
Polymorphism:- Literally many forms. Variations of chromosome appearance which are considered to be normal.
Polypeptide:- A molecule made up of a string of amino acids. A protein is a polypeptide.
Primer:- Short (perhaps 10-20 bp) preexisting polynucleotide chain to which new deoxyribonucleotides can be added by DNA polymerase.
Probe:- A small segment of DNA of known origin, designed to recognize complementary DNA on specific parts of chromosomes. The probe are usually labelled with a dye.
Probe:- Single- stranded DNA or RNA molecules of specific base sequence, labeled either radioactively, immunologically or FISH that are used to detect the complementary base sequence by hybridization.
Prokaryote:- Cell or organism lacking a membrane- bound, structurally discrete nucleus and other subcellular compartments. Bacteria are prokaryotes. Compare eukaryote. See Chromosomes.
Promoter:- A site on DNA to which RNA polymerase will bind and initiate transcription.
Prophylactic vaccine:- -a standard preventive vaccine.
Protein:- A large molecule composed of one or more chains of amino acids in a specific order; the order is determined by the base sequence of nucleotides in the gene coding for the protein. Proteins are required for the structure, function, and regulation of the bodys cells, tissues, and organs, and each protein has unique functions. Examples are hormones, enzymes, and antibodies.
Proteins:- The active molecules in all cells. Proteins control biochemical reactions and determine the physical structure of organisms.
Purine:- A nitrogen- containing, single- ring, basic compound that occurs in nucleic acids. The purines in DNA and RNA are adenine and guanine.
Pyrimidine:- A nitrogen- containing, double- ring, basic compound that occurs in nucleic acids. The pyrimidines in DNA are cytosine and thymine; in RNA, cytosine and uracil.
Quinacrine:- A chromosome stain specific for deoxyadenylate-rich regions in DNA.
Rare- cutter enzyme:- -See Restriction enzyme cutting site.
Rb:- Retinoblastoma gene.
Recessive gene:- A gene which must be present in both chromosomes of a pair to show outward signs of a certain characteristic.
Reciprocal translocation:- The breakage and exchange of material between 2 chromosomes without any gain or loss of genetic material. Such a reciprocal translocation is balanced and others unbalanced.
Recombinant clones: -Clones containing recombinant DNA molecules. See Recombinant DNA technologies.
Recombinant DNA molecules:- A combination of DNA molecules of different origin that are joined using recombinant DNA technologies.
Recombinant DNA technologies:- Procedures used to join together DNA segments in a cell- free system (an environment outside a cell or organism). Under appropriate conditions, a recombinant DNA molecule can enter a cell and replicate there, either autonomously or after it has become integrated into a cellular chromosome.
Recombinant DNA:- Hybrid DNA produced by splicing together segments of DNA from 2 or more organisms.
Recombinant genetic engineering (recombinant DNA technology)- –Genetic material from one organism is inserted into a foreign cell or another organism in order to mass-produce the protein encoded by the inserted genes.
Recombination:- Crossovers derive combinations of genes different from that of either parent.
Regulatory regions or sequences:- A DNA base sequence that controls gene expression.
Resolution:- Degree of molecular detail on a physical map of DNA, ranging from low to high.
Restriction enzyme cutting site:- A specific nucleotide sequence of DNA at which a particular restriction enzyme cuts the DNA. Some sites occur frequently in DNA (e.g., every several hundred base pairs), others much less frequently (rare- cutter; e.g., every 10,000 base pairs).
Restriction enzyme cutting site:- A specific sequence of DNA at which a particular restriction enzyme cuts the DNA.
Restriction enzyme, endonuclease:- A protein that recognizes specific, short sequences of DNA and cuts at those sites. See also Restriction enzyme cutting site.
Restriction enzyme, endonuclease:- A protein that recognizes specific, short nucleotide sequences and cuts DNA at those sites. Bacteria contain over 400 such enzymes that recognize and cut over 100 different DNA sequences. See restriction enzyme cutting site.
Restriction fragment length polymorphism (RFLP): Variation between individuals in DNA fragment sizes cut by specific restriction enzymes; polymorphic sequences that result in RFLPs are used as markers on both physical maps and genetic linkage maps. RFLPs are usually caused by mutation at a cutting site. See marker.
RFLP: See Restriction fragment length polymorphism.
Ribonucleic acid (RNA):- Related to DNA and responsible for translating the genetic code of DNA into proteins. A class of RNA found in the ribosomes of cells.
Ribonucleic acid (RNA):- The structure of RNA is similar to that of DNA. There are several classes of RNA molecules, including messenger RNA, transfer RNA, ribosomal RNA, and other small RNAs, each serving a different purpose.
Ribonucleotides:- See Nucleotide.
Ribosomal RNA (rRNA):- A class of RNA found in the ribosomes of cells.
Ribosome :- The small cellular structure in which RNA translates the genetic code into proteins.
Ribosomes:- Small cellular components composed of specialized ribosomal RNA and protein; site of protein synthesis. See ribonucleic acid (RNA).
Ring chromosome:- A chromosome which broke at each end lost the terminal segments, curled around and rejoined to form in a ring shape
RNA:- See Ribonucleic acid.
Robertsonian translocation:- Translocation exclusive to the acrocentric chromosomes (13,14,15,21,22), in which 2 chromosomes join near their centromeres, a fusion of 2 whole chromosomes. Robertson like Sutton was a student of McClung.
Sarcoma- Tumor of muscle fibers.
Satellites:- Small round appendages attached by fine stalks to the ends of the short (p) arms of the acrocentric chromosomes (13,14,15,21,22). They may be difficult to see. Satellites on different chromosomes are often attracted to one another, causing the acrocentric chromosomes to be satellite associated.
SC- Synaptonemal complex.
Segregation- The separation of the new sets of chromosomes.
SEM:- Scanning electron microscope.
Sequence tagged site (STS):- Short (200-500 bp) DNA sequence that has a single occurrence in the human genome and whose location and base sequence are known by PCR. Expressed sequence tags (ESTs) are STSs derived from cDNAs.
Sequence:- See Base sequence.
Sequencer:- An apparatus used for deciphering the order of bases in a stra nd of DNA.
Sequencing:- Determination of the order of nucleotides (base sequences) in a DNA or RNA molecule or the order of amino acids in a protein.
Sex Chromosome:- The X and Y chromosomes which are responsible for sexual development. In humans, females have XX chromosomes and males have XY.
Sex chromosomes:- The X and Y chromosomes in human beings that determine the sex of an individual. Females have 2 X chromosomes; males have one X and one Y.
Sex chromosomes:- The X and Y chromosomes in human beings that determine the sex of an individual. Females have two X chromosomes in diploid cells; males have an X and a Y chromosome.
Shotgun method:- Cloning of DNA fragments randomly generated from a genome. See Library, Genomic library.
Single strand: One half of a DNA double helix.
Somatic cells:- Cell of the body except sex cells.
Southern blotting: Transfer by absorption of DNA fragments separated in electrophoretic gels to membrane filters for detection of specific base sequences by radiolabeled complementary probes.
STS:- See Sequence tagged site.
Submetacentric:- Chromosomes with centromeres off center. The chromosome arms are of unequal length.
Synaptonemal complex:-- Tripartite proteinaceous ladder composed of axial elements (cores) holding early pairs of aligned homologues--synapsing sister chromatids.
Syndrome:- A group of symptoms, occurring together, which characterise a disease.
Systemic immunity- – Same as antibody-mediated or humoral immunity.
Tandem repeat sequences:- Multiple copies of the same base sequence on a chromosome; used as a marker in physical mapping.
T-cells (T lymphocytes):- – White blood cells (lymphocytes) that mature in the thymus and participate in immune defenses. They are cytotoxic T-cells and helper T-cells.
Technology transfer:- The process of converting scientific findings from research laboratories into useful products by the commercial sector.
Telomere:- The ends of chromosomes. These specialized structures are involved in the replication and stability of linear DNA molecules. See DNA replication.
TEM- Transmission electron microscopy.
Template:- a single DNA strand that serves as pattern for building a new second strand.
Tetraploidy:- The presence in a cell of 4 haploid sets of parental chromosomes, thus a count 92 in humans.
Tetrasomy:- The presence of 4 instead of 2 of a particular chromosome.
Therapeutic vaccine a vaccine for treatment-
Thymine (T):- A nitrogenous base, one member of the base pair A- T (adenine- thymine). Always bonds with adenine (T-A).
Transcription:- The synthesis of an RNA copy from a sequence of DNA (a gene); the first step in gene expression. Compare translation.
Transfer RNA (tRNA):- A class of RNA having structures with triplet nucleotide sequences that are complementary to the triplet nucleotide coding sequences of mRNA. The role of tRNAs in protein synthesis is to bond with amino acids and transfer them to the ribosomes, where proteins are assembled according to the genetic code carried by mRNA.
Transformation:- A process by which the genetic material carried by an individual cell is altered by incorporation of exogenous DNA into its genome.
Translation:- The process in which the genetic code carried by mRNA directs the synthesis of proteins from amino acids. Compare transcription.
Translocation:- The fusion or exchange of material between chromosomes. When there is no gain or loss of material, the translocation is said to be balanced; when there is gain or loss, resulting in trisomy or monosomy for a particular chromosome segment, it is unbalanced.
Triploidy:- The presence in a cell of 3 haploid sets of parental chromosomes, giving a total chromosoome count of 69 for humans.
Trisomy:- The presence of 3 copies of a particular chromosome like 21 for Down's syndrome. Three copies of part of a chromosome is partial trisomy.
tRNA:- See Transfer RNA. Virus:-A noncellular biological entity that can reproduce only within a host cell.
Uniparental disomy:- Both members of a chromosome pair are contributed by one parent rather than one from each parent. Was there a nondisjunction?
Uracil:- A nitrogenous base normally found in RNA but not DNA. Uracil can form a base pair with adenine.
Vector:- See Cloning vector.
Virus:- A noncellular biological entity that can reproduce only within a host cell. Viruses consist of nucleic acid covered by protein; some animal viruses are also surrounded by membrane
VLSI:- Very large-scale integration allowing over 100,000 transistors on a chip.
X-chromosome:- Female sex chromosome.
X-Linked gene:- Any gene which is located on the X chromosome.
X-Linked Recessive Mutation:- A recessive mutation in a gene carried on the X chromosome.
YAC:- Yeast artificial chromosome.
Y-chromosome:- Male sex chromosome
Yeast artificial chromosome (YAC):- A vector used to clone DNA fragments (up to 400 kb). Constructed from the telomeric, centromeric and replication origin sequences needed for yeast cells. Compare Cloning vector, Cosmid.
Zygote:- Fertilized ovum or other cell. Through mitosis, the zygote develops into a multicellular embryo or a cell line.