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Gene Expression
Level 2Biology
Term | Definition |
---|---|
Allele | One of the alternative forms of a gene. |
Amino acids | Any of a group of water-soluble organic compounds that possess both a carboxyl(-COOH) and an amine (-NH2) group attached to the same carbon atom. |
Anticodon | A sequence of three nucleotides on a tRNA molecule that matches with a specific codon on a strand of mRNA during translation. |
Centromere | The part of a chromosome that attaches to the spindle during cell division. |
Chromatid | A threadlike strand formed from a chromosome during the stages of cell division. |
Chromosome | A threadlike structure made of DNA and (in eukaryotes) associated histone proteins on which the genetic information of an individual is stored. |
Cloning | artificial production of genetically identical individuals |
Co-dominance | The condition that arises when both alleles in a heterozygous organism are dominant and fully expressed - eg. the human blood group AB. |
Codon | A triplet of nucleotides within a molecule of messenger RNA that specifies a particular amino acid during the synthesis of proteins in a cell. |
Diploid | Describing a cell or organism with twice the haploid number of chromosomes. |
DNA | Deoxyribonucleic acid. The genetic material of most living organisms. It plays a central role in the determination of hereditary characteristics by controlling protein synthesis in cells. |
Dominant allele | The allele that is expressed when two different alleles of a gene are present in the cells of an organism. It is denoted by a capital letter. |
Double Helix | ladder-like molecule twisted into a helix |
Eukaryotic cells | Cells that have a distinct nucleus where the cell’s genetic information is stored. |
F1 generation | The first generation of offspring resulting from an arranged cross between selected parents in breeding experiments. |
F2 generation | The second generation of offspring in breeding experiments, obtained by crosses between individuals of the F1 generation. |
Fertilization | fusing of an egg and sperm |
Gametes | A reproductive cell that fuses with another to form a zygote - eg. eggs (ova) and sperm (spermatozoa). |
Gene | A section of DNA that codes for a particular protein and cannot be broken by recombination. |
Genetic code | The genetic information in DNA which controls the manufacture of specific proteins by the cell. It takes the form of a series of triplets of bases in DNA. |
Genome | All the genes contained in a single (haploid) set of chromosomes. |
Genotype | The genetic composition of an organism, i.e. the combination of alleles it possesses. |
Haploid | Describing a cell or organism with a single set of unpaired chromosomes. |
Heterozygous | Describes an organism that has two different alleles controlling a particular feature. |
Histone | Water-soluble proteins found in association with the DNA of eukaryotic chromosomes. They serve as a scaffold around which the DNA coils. |
Homologous Chromosomes | Matching pairs of chromosomes, i.e. Chromosomes that have the same structural features. In diploid cells, one chromosome comes from the female parent, the other from the male parent. |
Homozygous | Describes an organism that has two of the same alleles for a trait. |
Incomplete dominance | The condition where neither allele controlling a characteristic is dominant and the resulting phenotype is partially influenced by both alleles. |
Independent assortment | The separation of the alleles of one gene into gametes independently of the way in which the alleles of other genes have segregated. |
Inheritance | The transfer of genetic traits from one generation to the next. |
Lethal genes | A mutant form of a gene that eventually results in the death of an organism if expressed in the phenotype. Most of these genes are recessive, eg. Sickle-cell anaemia. |
Meiosis | A type of cell division that gives rise to four gametes each with half the chromosome number of the parent cell. |
Mitosis | A type of cell division that results in two daughter cells, each having a nucleus containing the same number and kind of chromosomes as the mother cell. |
Monohybrid | The offspring of a cross between parents that differ in the alleles they possess for one particular gene, one parent having two dominant alleles, the other two recessives. |
mRNA | RNA that carry’s the genetic code transcribed from DNA to the ribosomes. |
Nucleotide | An organic compound consisting of a nitrogen-containing purine or pyrimidine base linked to a sugar and a phosphate group. |
Phenotype | The observable characteristics of an organism. |
Protein synthesis | The process by which living cells assemble amino acids into proteins based on the genetic information carried in the DNA of the chromosomes. |
Purines | The chemical family to which the organic nitrogenous bases adenine and guanine belong. |
Pyrimidines | The chemical family to which the organic nitrogenous bases uracil, thymine and cytosine belong. |
Recessive allele | An allele whose effects are masked by those of a dominant allele. It is denoted by a lower case letter. |
rRNA | A type of RNA that is present in the ribosomes. |
DNA-Replication | ability of DNA molecules to make identical copies of themselves |
Somatic cells | All cells in the body other than the reproductive cells. |
Trait | feature whose appearance is determined by genes (inherited) |
Transcription | The process in living cells in which the genetic information of DNA is transferred to a molecule of mRNA as the first step in protein synthesis. |
Translation | The process in living cells in which a sequence of mRNA triplets (codons) is used to build a polypeptide chain during protein synthesis. |
Triplet | A sequence of three nucleotides coding for a specific amino acid during protein synthesis. |