Genetics Common Terminologies - Study Material for B.Sc. Botany Hons.
This study material covers common genetic terminologies from A to I, including definitions of key terms such as allele, allopolyploid, amorph, anaphase, biotype, and more. The content explains concepts like genetic inheritance, chromosome behavior, and molecular biology fundamentals relevant to the field of botany. It provides valuable insights into genetic principles and terminology essential for students pursuing a B.Sc. in Botany Hons.
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GENETICS: COMMON TERMINOLOGIES Part I (A to I) Study Material for B.Sc. Part II Botany Hons. Paper IV Dr. Pushpanjali Khare Sr. Asstt. Professor & Head, Deptt. of Botany MMC (PU) Patna
A A ALLELE: One of a pair, or series, of alternative forms of a gene that occur at a given locus in a chromosome. Alleles are symbolized with the same basic symbol (e.g., D for tall peas and d for dwarf). ALLOPOLYPLOID: A polyploid having chromosome sets from different species. A polyploid containing genetically different chromosome sets derived from two or more species. ALLOZYGOTE: A diploid individual in which the two genes of a particular locus are not identical by descent from a common ancestor. AMINO ACID: Any one of a class of organic compounds containing the amino (NH2) group and carboxyl (COOH) group. Amino acids are building blocks of proteins. Alanine, proline, threonine, histidine, lysine, glutamine, phenylalanine, tryptophan, valine, arginine, tyrosine, and leucine are common among amino acid. AMORPH: Amutation that obliterates gene function; a null mutation. ANAPHASE: The stage of mitosis or meiosis during which the daughter chromosomes pass from the equilateral plate to oposite poles of the cell (towards the ends of the spindle). Anaphase follows metaphase and precedes telophase. ANEUPLOID (HETEROPLOID): An organism or cell having a chromosome number that is not an exact multiple of the monoploid (n ) with one genome, that is, a hyperploid has a higher number(e.g., 2n+1) and a hypoploid has a lower number (e.g., 2n-1). Also applied to cases where part of a chromosome is duplicated or deficient.
B B BACKCROSS: The cross of an F1 hybrid to one of the parental types. The offspring of such a cross are referred to as the backcross progeny. BALANCED LETHAL: Lethal mutations in different genes on the same pair of chromosomes that remain in repulsion because of close linkage or crossover suppression. In a closed population, only the trans-heterozygotes (l1+/l2) for the lethal mutation survive. BALANCED POLYMORPHISM: Two or more types of individuals maintained in the same breeding population. BARR BODY: A condensed mass of chromatin found in the nuclei of the placenta mammals that contains one or more X chromosomes. Named for its discover Murray Barr. BINOMIAL-EXPANSION: Exponential multiplication of an expression consisting of two terms connected by a plus (+) or a (-) sign, such as (a+b)^n. BIOMETRY:Application of statistical methods to the study of biological problems. BIOTYPE: Distinct physiology race or strain within morphological species. A population of individuals with identical genetic constitution. A biotype may be made up of homozygotes or heterozygotes, of which only the former would be expected to breed true.
B & C BIPARTITE: Consisting of the two identifiable parts. BIVALENT: A pair of synapsed or associated homologous chromosomes that have undergone the duplication process to form a group of four chromatids. BROAD-SENSE HERITABILITY: In quantitative genetics, the proportion of the total phenotypic variance that is the genotypic variance. CHROMATID: In mitosis or meiosis, one of the two identical strands resulting from self-duplication of a chromosome. CHROMATIN: The deoxyribonucleohistone in a chromosome; originally named after the readiness with which it stain with certain dyes.(chromaticity) CHROMOCENTER: Body produced by fusion of the heterochromatic regions of chromosomes in the polytene tissues (e.g., the salivary glands) of certain Diptera. CHROMOMERES: Small bodies, described by J. Belling, that are identified by their characteristic size and linear arrangement along a chromosome. CHROMOSOME ABERRATION: Abnormal structure or number of chromosomes; includes deficiency, duplication, inversion, translocation, aneuploidy, polyploidy, or any other change from normal pattern.
C CHROMOSOME BANDING: Staining of chromosomes in such a way that light and dark areas occur along the length of the chromosomes. Lateral comparison identify pairs. Each human chromosome can be indentified by its banding pattern. CHROMOSOMES: Darkly staining nucleoprotein bodies that are observed in cells during division. Each chromosome carries a linear array of genes. CISTRON: A unit of function in DNA. One DNA cistron specifies one polypeptide chain in protein synthesis. CODON: A set of three adjacent nucleotide in an mRNA molecule that specifies the incorporation of an amino acid into a polypeptide chain or that signals the end of polypeptide synthesis. Codons with the latter function are called termination codons. COINTEGRATE: A DNA molecule formed by the fusion of two different DNA molecules, usually mediated by a transposable element. COLCHICINE: An alkaloid derived from the autumn crocus that is used as an agent to arrest spindle formation and interrupt mitosis. COMPETENCE:Ability of a bacterial cell to incorporate DNA and become genetically transformed. CONTROLLING ELEMENT: In maize, a transposable element such as a Ac or Ds that is capable of influencing the expression of a nearby gene.
C & D COUPLING: The condition in which a double hetrozygote has received two linked mutations from one each parent and their wild-type alleles from the other parent.eg.,a b/a b x++/++ produced ab/++. CROSS BREEDING: Mating between members of different races or species. CROSSING-OVER: A process in which chromosomes exchange material through the breakage and reunion of their DNA molecules. CROSSOVER UNIT: A measure of distance on genetic maps that is based on the average number of crossing-over events that takes place during meiosis. A map interval that is one crossover unit in length (sometimes called a centimorgan) implies that only one in every hundred chromatids recovered from meiosis will have undergone a crossing over event in this interval. CYTOGENETICS: Area of biology concerened with chromosomes and their implication in genetics. CYTOKINESIS: Cytoplasmic division and other changes exclusive of nuclear division that are a part of mitosis or meiosis. CYTOLOGY: The study of structure and functions of cells. DISJUNCTION: Separation of homologous chromosomes during anaphase of mitotic or meiotic divisions. DOMINANCE: A condition in which one member of an allele pair is manifested to the exclusion of the other.
E ENDOMITOSIS: Duplication of chromosomes without division of the nucleus, resulting in increased chromosome number within a cell. Chromosome strands separate but the cell does not divide. ENDOPOLYPOIDY: A state in which the cells of a diploid organisms contain multiples of the chromosome number (i.e., 4n, 8n, etc.) EPIGENETIC:A term referring to the non genetic causes of a phenotype. EPISOME: A genetic element that may be present or absent in different cells and that may be inserted in a chromosome or independent in the cytoplasm. For example, the fertility factor (F) in Escherichia coli. EPISTASIS: Interactions between products of non allelic genes. Genes suppressed are said to be hypostatic. Dominance is associated with members of allelic pair, whereas epistasis is interaction among the products of non alleles. EUCHROMATIN: A part of chromosome with normal staining properties; apparently contains most of the genes; most active part of chromosome. EXON: The Intervening sequence of Gene (Intron-Exon-Intron) that are retained in messenger RNA; A region of genes which is actually expressed.
F & G FOOT PRINTING:A technique to determine the length of nucleic acid in contact with a protein FORWARD MUTATION: A change from wild type allele to a mutant allele FRAME SHIFT MUTATION: A mutational event caused by the insertion of deletion of one or more nucleotide pairs in a gene, resulting in a shift in the reading frame of all codons following the mutational site. FUNCTIONAL ALLELES: Mutations that fail to complement each other in a cis-trans complementation test. GAMETE: A mature male or female reproductive cell (sperm or egg). GAMETOPHYTE: That phase of the plant life cycle that bears the gametes; the cell n chromosomes. GENE: A hereditary determinant of a specific biological content function; a unit of inheritance (DNA) located in a fixed place in a chromosome. GENETIC CODE: The set of 64 triplets of bases (codons) that correspond to the 20 amino acids in protein and the signals for initiation and termination of polypeptide syntehsis
G & H GENE FLOW: The spread of genes from one breeding population to another by migration, possibly leading to allele frequency changes. GENE POOL: The sum total of all different alleles in the breeding member of a population at a given time. GENETICS: The signs of heredity and variation. GENOME:A complete set of (n) of the chromosomes (hence, of genes) inherited as a unit of one parent. GENOTYPE: The genetic constitution(gene makeup) of an organism GERM-PLASM: The hereditary materials transmitted to the offspring. HAPLOID(MONOPLOID):An organism or cell having only one complete set(n) of chromosomes or one genome. HEMIZYGOUS: The condition in which only one allele of the pair id present, as in sex linkage or as a result of deletion. HEREDITY: Resemblance among individuals related by descent; transmission from parents to offspring. HETERODUPLEX: A double-stranded nucleic acid containing one or more mismatched (non-complimentary) base pairs. HETEROGAMETETIC SEX: Producing unlike gamete with regards to the sex chromosomes. In humans XY male is heterogametic and XX female is homogametic
H HETEROSIS: Superiority of heterozygous genotypes in respect to one or more traits in comparison with corresponding homozygote. HETEROZYGOTE: An organism with unlike members of any given pair or series of allele that consequently produces unlike gametes. HISTONES: Group of proteins rich in amino acids. They function in the coiling on DNAin chromosomes. In the regulation of gene activity. HOLANDRIC GENE: Agene carried on the Y chromosome and transmitted from the father to son. HOMEOBOX: A DNA sequence found in several genes that are involved in the specification of organs in different body parts in animal; characteristic of genes that influence the segmentation in animal. The homeobox corresponds to an amino acid sequence I the polypeptide encoded by these genes; this sequence is called homeodomain. HOMEOTIC MUTATION: A mutation that causes a body part to develop in an inappropriate positon in an organism. For example, a mutation in drosophila that causes its leg to grow on the head in place of the antennae. HOMOGAMETIC SEX: Producing like gametes with regard to the sex chromosomes.
H & I HOMOLOGOUS CHROMOSOMES: A chromosomes that occurs in pairs and are generally similar in size and shape, one having come from the male parent and the other from the female parent. Such chromosomes contain the same array of genes. HYBRID: An offspring of homozygous parents differing in one or more genes; more generally, an offspring of a cross between unrelated strains. HYBRID DYSGENESIS: In drosophila, a syndrome of abnormal germ line traits, including mutation, chromosome breakage, and sterility, that results from transposable element activity. HYBRID VIGOR(HETEROSIS): Unusual growth, strength, health, of heterozygous hybrid from two less vigorous parents. HYPOMORPH: A mutation that reduces but does not completely abolish gene expression. INCOMPLETE DOMINANCE: Expression of two alleles in a heterozygote that allows the heterozygote to be distinguished from either of its homozygous parents. INDEPENDENT ASSORTMENT: The random distribution of alleles to the gametes that occurs when genes are located in different chromosomes. The distribution of one pair of alleles is independent of other pair of gene located in non- homologous chromosomes.
I INDUCER: A substance of low molecular weight that inactivates a repressor by combining with it, there by stimulating gene expression. INITIATION: The beginning of protein synthesis. INITIATION CODON: The messenger RNA sequence AUG, which specifies Methionine, the first amino acid used in translation process INHIBITOR: Any substance or object that retards a chemical reaction; a major or modifier gene that interferes with a reaction. In Situ: from the latin, meaning In the natural place. Refers to experimental treatments performed on cells or tissues rather than on extracts from them. In vitro : Biological or chemical work done in the test tube rather than the living system. TO BE CONTD. IN PART II .
