Ch4 Genetic Information

• Adaptation


  A feature of an organism that increases its chance of survival in its environment. An adaptation may be anatomical, physiological or behavioural.
• Allele


  A version of a gene
• Anticodon


  A sequence of three nucleotide bases at one end of a tRNA molecule that is specific to an mRNA codon
• Arithmetic mean


  The average of a set of numbers calculated by dividing the sum of the values by the number of values
• Artificial classification


  A type of classification that divides organisms into groups based on analogous characteristics such as leaf shape, number of legs and type of wing
• Binomial system


  A universal system of naming organisms that consists of two parts: the generic name and the specific name, e.g. Homo sapiens
• Biodiversity


  The variety of genes, species and habitats within a particular area
• Cellular proteome


  The proteins expressed in a given type of cell
• Chromatid


  One strand of a replicated chromosome
• Chromosome


  A structure consisting of a long, coiled molecule of DNA and its associated proteins, by which genetic information is passed from generation to generation
• Chromosome mutation


  A change to the number or structure of chromosomes that can occur spontaneously
• Classification


  The organisation of organisms into groups. There are two types of classification: artificial and phylogenetic
• Codon


  A sequence of three bases on mRNA that codes for a specific amino acid
• Conservation


  The maintenance of ecosystems and biodiversity by humans in order to preserve the Earth's resources
• Courtship


  The behaviour by which members of a species select reproductive partners. It enables organisms to recognise their own species, identify a mate with a capacity to breed, form a pair bond, synchronise mating and become able to breed themselves
• Crossing over


  The process in meiosis 1 in which homologous chromosomes pair up, their chromatids wrap around one another and their alleles are exchanged at equivalent portions of chromatids. This creates genetic variation
• Degenerate


  A feature of the genetic code; more than one triplet can code for a particular amino acid
• Deletion


  A form of gene mutation in which one or more nucleotide bases are removed from a DNA sequence. This may change all amino acids in a sequence, rendering the protein non-functional
• Directional selection


  A type of selection that favours individuals that differ in one direction (fall to the left or the right) from the population mean. This changes the traits of the population
• Ecosystem diversity


  A measure of the range of different habitats in a particular area
• Eukaryotic DNA


  Linear molecules of DNA which, together with histones, form chromosomes. DNA in the mitochondria and chloroplasts of eukaryotic cells is circular and does not have associated proteins
• Exon


  A sequence of DNA that codes for an amino acid sequence
• Fertilisation


  The random fusion of haploid gametes during fertilisation to produce a diploid zygote. Genetic information is mixed, creating genetic variation
• Gene


  A length of DNA on a chromosome that codes for the production of one or more polypeptide chains and functional RNA
• Gene mutation


  A change to at least one nucleotide base in DNA or the arrangement of bases. Gene mutations can occur spontaneously during DNA replication
• Generic name


  Denotes the organism's genus. The first letter is written in upper case, e.g. Homo
• Genetic code


  The rules by which triplets in a DNA base sequence code for the sequence of amino acids in a polypeptide chain. The genetic code is degenerate, universal and non-overlapping
• Genetic diversity


  The number of different alleles in a population. Genetic diversity between organisms can be investigated by comparing observable characteristics, DNA and mRNA base sequences and amino acid sequences
• Genome


  The entire set of genes in a cell
• Histones


  Proteins that, together with DNA, form chromosomes in the nuclei of eukaryotic cells
• Homologous chromosomes


  A chromosome pair, one paternal and one maternal, with the same gene loci
• Independent segregation


  The random separation of homologous chromosomes in meiosis 1 that produces genetic variation
• Index of diversity (d)


  Describes the relationship between the number of different species and the abundance of individuals in each of these species within a community. It is calculated using the formula: d = 1 - Σ(n/N)^2 where d is the index of diversity, N is the total number of organisms of all species and n is the total number of organisms of each species
• Intron


  A non-coding sequence of DNA
• Locus


  The position of a gene on a chromosome
• Mean (normal distribution curve)


  A measure of the maximum height of a normal distribution curve
• Meiosis


  A type of cell division that produces four genetically different daughter cells (gametes) with a haploid number of chromosomes. It involves two divisions
• Messenger RNA (mRNA)


  A type of RNA that carries genetic information from the nucleus to the ribosomes for protein synthesis. It is a single helix consisting of thousands of mononucleotides
• Mitosis


  A form of cell division that produces two genetically identical diploid daughter cells
• Mutagenic agent


  An agent that increases the rate of gene mutations above normal level