Glossary

Allele: a form of a gene, having a different nucleotide sequence than other forms of the gene. Many variations of alleles for a trait may exist in a species. For example, the gene that codes for blood type has alleles for blood types A, B and O distributed among all the people in the world; but any one person can only have two alleles, e.g. AA, or BO, or other combinations.

Amino Acid: small molecules that are joined together to form proteins. There are twenty primary amino acids that form the proteins needed by organisms. Each is coded for by three sequential DNA letters of a gene. Most animals cannot make all of these twenty primary amino acids, and must have certain ‘essential amino acids’ in their diets.

Anticodon: a set of three tRNA bases that match (complement) a set of three mRNA bases.

Autosome: a chromosome that is not a sex chromosome. The human genome has 22 autosome pairs, plus 1 pair of sex chromosomes (= 23 pairs of chromosomes, or 46 chromosomes in total).

Backcross: a mating between an offspring and one of its parents.

Base: one of four small molecules attached to the sugar-phosphate backbone of DNA or RNA. Specific sequences of three bases serve as a code for each amino acid. Adenine (A), Guanine (G), Thymine (T), and Cytosine (C) occur in DNA; Uracil (U) replaces Thymine in RNA.

Base Pair: two matched (complementary) nucleic acid bases held together with a hydrogen bond. In DNA, the base Adenine (A) pairs with Thymine (T), and Guanine (G) pairs with Cytosine (C). In RNA, Uracil (U) pairs with Thymine, and Guanine with Cytosine. The hydrogen bonds of base pairs hold strands of the DNA helix together.

Bioinformatics: applying computer technology to biology. Analysis of DNA or protein sequence patterns can answer questions about gene functions. Bioinformatics is especially important in fields of health, evolution, environmental studies, and others.

Breeding: mating and producing offspring. Organisms of different breeds but of the same species usually can mate with each other, but organisms of different species usually cannot mate with each other. E.g. different breeds of dogs can mate and produce puppies, but a dog and a cat cannot mate.

Carrier: a heterozygous organism that has, but does not usually express, a recessive trait. A carrier has inherited a dominant allele from one parent, and a recessive allele from the other parent.

Chromosome: a long, continuous strand of DNA attached to several proteins. When it is said that “chromosomes contain genes”, these genes are sequences of nucleotides along the DNA molecule that is part of the chromosome. All of the chromosomes in one cell of an organism are referred to as the organism’s genome.

Claim: an assertion or conclusion addressing the original question or problem being investigated.

Codon: Three DNA or mRNA bases that code for one amino acid.

Complementary: A term used in genetics that refers to the regular way nucleotide bases pair with each other. A pairs with T (U in RNA) and G pairs with C. Each base pair is joined by hydrogen bonds.

Crossover: exchange of genetic material during meiosis. During meiosis, homologous chromosomes swap like segments. Crossovers are a contributing factor to the variation between offspring of the same parents.

Crossing: breeding two parent organisms to produce offspring.

Diploid: (2n), a cell or organism that has two complete sets of chromosomes for that organism. Diploid refers to the chromosome number normally found in a ‘body’ cell, and twice the chromosome number normally found in an egg or sperm cell of that organism. Generally, a normal eukaryote is diploid, which means it has one set of chromosomes from its mother, and another set of chromosomes from its father.

DNA: (deoxyribonucleic acid), the molecule that makes up genes, and is often called the “hereditary material”. DNA is a double stranded nucleic acid made of deoxyribose sugar; phosphate groups (the atom phosphorous plus some oxygen atoms); and the bases A, T, G, and C. The two strands are held together by hydrogen bonds between the paired bases.

DNA Sequence: the order of bases (A, T, G, and C) in a strand of DNA.

Dominant: a term used when one form of a gene (allele), in combination with another allele, has sole impact on the phenotype observed. Dominant refers to both the allele and the phenotype. Dominant does NOT mean stronger, nor more common.

Double helix: the shape a DNA molecule takes when its two strands twist around each other.

Enzyme: a protein that speeds up a chemical reaction. For example, the enzyme amylase in saliva is responsible for breaking down starch into sugar.

Epistasis: a gene interaction where one gene masks another one. For example, a primary gene that affects color in some mice will produce mice that are either black or brown; however if a mouse also has a gene for the albino trait, the mouse will be white no matter what combination of black or brown alleles are present for that gene.

Evidence: scientific data that is appropriate and sufficient to support a claim. This data may come from investigations, observations, archived data, or other data sets or reading material. Data must be appropriate and relevant to the problem and sufficient to convince others of the validity of the claim.

Expressed, or expression: transcription of DNA into mRNA and then translation of the mRNA into a protein. A gene that is expressed is also said to be “turned on”.

F1F2 and P generations: terms used to describe observed or intentionally bred generation. P = the Parent generation; F1 = the children, or the first filial generation; and F2 =the grandchildren, or the second filial generation.

Frameshift: a mutation caused by deletion or insertion of one or more bases (excluding multiples of three) into a gene. A frameshift mutation changes ‘reading’ of the DNA codons so that it may not make a useful protein. By analogy, if you took the first letter “a” out of the sentence “Shepatthefatcat” (She pat the fat cat), but kept 3-letter clusters, you might have “Sheptthefatcat” (She ptt hef atc at), which is not a useful sentence.

Gamete: an egg or sperm. Haploid (1n) cells produced by meiosis.

Gene: a section of DNA that usually codes for a protein. These proteins are molecules that contribute to traits,whether physical or biochemical. Genes are strung together into long molecules of DNA; genes do not exist as separate pieces of DNA.

Genetic Code: the sequence of DNA bases (A, T, G, and C) that codes for traits. Each three letters of DNA code for three letters of RNA, which code for one amino acid. There are 64 possible ways to combine the four DNA bases into three-letter “codes”; but there are only 20 primary amino acids. So there are several ways to code for most of these 20 amino acids. This means there can be some mutations in a gene’s DNA sequence that will not change the amino acid sequence of the protein, so the relevant trait is not affected.

Genetic cross: mating two parent organisms to produce offspring, generally to investigate a specific genetically determined trait or traits.

Genome: all of the genetic material of an organism. One set of the chromosomes in one cell of an organism. In eukaryotes, "genome" usually refers only to the nuclear DNA and excludes the mitochondrial or chloroplast DNA.

Genomics: the study of genomes. The study of how genes function and interact.

Genotype: the collection of genes that an organism has; also the set of alleles inherited. Generally we only consider one or a few genes at a time when talking about an organism’s genotype. The complete genotype for an organism is described by its complete genome sequence.

Haploid: (n), one complete set of chromosomes for an organism. The chromosome number normally found in an egg or sperm. Haploid cells have half the number of chromosomes that other cells in an organism have; haploid cells may be joined together to create a new diploid cell, which could develop into a whole organism (an offspring, or baby). Older texts may use the term ‘monoploid’.

Heterozygous: having two different alleles of a gene, such as Tt.

Homologous chromosomes: also called homologs, or partner chromosomes, i.e. pairs of similar chromosomes in a cell. For example, in the genome of an organism, chromosome 1 inherited from the father, is a homolog of chromosome 1 inherited from the mother. X and Y chromosomes are also a homologous pair, although they share comparatively less DNA with each other than the autosomes do.

Homologous recombination: See Crossover.

Homozygous: having two copies of the same allele of a gene, such as TT or tt.

Hybrid: a heterozygous offspring of two different homozygous parents. For example, a parent homozygous for one version of a trait, AA, bred with a parent homozygous for another version of the trait, aa, produces a “hybrid” offspring that is heterozygous for the trait, Aa. The phenotype depends on the interaction between the two different gene products.

Incomplete dominance: a term used when the phenotype of an organism heterozygous at a particular gene displays a phenotype intermediate between the two homozygous possibilities. For example, in some carnations, a pure white flower bred with a pure red flower produces offspring with pink flowers.

Independent Assortment: the process during meiosis when the alleles of one gene separate independently from the alleles of another gene. This can occur when the two genes are on different chromosomes, or when they are far enough apart on the same chromosome. The gametes that represent all possible combinations of these two traits occur with equal frequency.

Inherited Trait: a specific characteristic that is passed on to an organism through its parents’ DNA. In drakes features such as Wings, Forelimbs, Tail shape, Color, and Armor are inherited traits.

Linkage: The tendency for genes or segments of DNA closely positioned along a chromosome to segregate together at meiosis and therefore be inherited together. Linked genes do not have to be right next to each other on a chromosome.

Locus: the location where a gene is on a chromosome.

Meiosis: a special cell division that produces sperm or egg cells. Meiosis is a special kind of cell division in which two divisions follow a single round of DNA replication. In the first division,homologous chromosomes segregate from each other to form haploid cells (those with only 1 complete set of chromosomes). In the second division the chromosome copies formed during replication separate from each other. Meiosis creates new cells that are NOT genetically identical to the original cell.

Mitosis: a division process that creates two identical daughter cells from a single cell.

Mitosis creates new ‘body’ cells that are genetically identical to the original cell. (See Meiosis for the creation of new ‘sex’ cells.) Mitosis is what is happening when organisms grow bigger, replace things like skin cells or leaves, and repair things like broken bones or rips made when a tree branch breaks off.

Multiple Genes: also called multigenic or polygenic; a form of inheritance in which more than one gene affects a trait. Color is often determined by multiple genes, e.g. coat color in dogs, or eye, hair and skin color in humans. Other traits with continuous variation, such as height, are also often governed by multiple genes.

Mutation: any change in the DNA sequence of a gene. A mutation in the DNA of an egg or a sperm can be inherited, while a mutation in the DNA of a ‘body’ cell, such as a skin or a leaf cell, cannot be inherited.

Nucleic acid: DNA or RNA. Nucleic acids are made of strands of sugar (deoxyribose or ribose); phosphate groups (the atom phosphorous plus some oxygen atoms); and four bases (A, T, G, and C in DNA or A, U, G, and C in RNA). Nucleic acids store and express, the hereditary information of all organisms.

Offspring: direct descendants in a family line (e.g. children of a parent).

PF1 and F2 generations: terms used to describe observed or intentionally bred generations. P = the Parent generation; F1 = the children, or the first filial generation; and F2 = the grandchildren, or the second filial generation.

Phenotype: the form of a trait that an organism shows. Not all phenotypes are physical like color or height. There are also behavioral and metabolic phenotypes that are not visible. Phenotypes can be influenced by single genes, multiple gene interactions, and/or the environment.

Polygenic: many genes governing a single trait. Researchers are beginning to see that most traits are polygenic, such as height or skin color which have continuous gradations. The pea traits Geniverse Drake Breeder’s Glossary 7 that Gregor Mendel used in his work are examples of traits determined by single genes (e.g. pea color is green or yellow with no variation in between).

Protein: a chain of amino acids. Proteins carry out a wide variety of jobs, for example enzymes speed up chemical reactions; hormones carry messages; and structural proteins are the main parts of muscle, hair, and seeds. Proteins are the specific molecules that produce a trait such as pigment color in drakes.

Reasoning: in argumentation- statements that link the evidence to the claim, showing why the data counts as evidence to support the claim. Reasoning often includes appropriate scientific principles. Reasoning is related to a “conclusion” but is less formal; reasoning is a necessary step at every stage of a scientific investigation, while a conclusion generally comes at the end of a carefully designed set of experiments.

Recessive: a term used when a particular allele has an impact on the phenotype observed only when in combination with a similar allele. Recessive refers to both the allele and the phenotype. Recessive does NOT mean weaker, nor less common.

RNA: (ribonucleic acid) is a small nucleic acid that works to translate a DNA sequence into a protein. RNA is a single strand nucleic acid made of ribose sugar; phosphate groups (the atom phosphorous plus some oxygen atoms); and the bases A, U, G, and C. A strand of RNA is constructed following the DNA code, then is used by the cell to assemble a specific sequence of amino acids. In eukaryotes, RNA carries the DNA code from the nucleus into the cytoplasm. There are three common forms of RNA (mRNA, tRNA, and rRNA), all of which play specialized roles in converting the DNA code into proteins that contribute to traits.

mRNA: messenger RNA. This is a copy of a gene along the DNA into RNA; mRNA works as a code for assembling amino acids into protein chains.

tRNA: transfer RNA. These molecules work to transport amino acids within a cell's cytoplasm to the ribosomes for assembling into a protein, following the code spelled out by the mRNA.

rRNA: ribosomal RNA. These RNA molecules combine with specialized proteins to form ribosomes. The mRNA, tRNA and amino acids come together in the ribosomes which assist in linking together the amino acids to form protein chains.

Segregation: separation of chromosome pairs, or different alleles of the same gene, when a cell divides in meiosis. Segregation results in eggs or sperm that have only one of the parent chromosomes for each chromosomal pair.

Sex Chromosome: In mammals, an X or Y chromosome, the pairing of which determines the sex of the offspring. Generally in mammals XX is a female, and XY is a male. The Y chromosome is shorter than the X chromosome and does not have the same set of genes found on the X. This fact is important for sex-linked traits. Sex determination of living things is not standard; in different species, there may be different sex chromosomes, different groupings of sex chromosomes, and/or environmental impacts.

Sex Linked: traits that are determined by genes on the X or Y chromosome. Since females have two copies of the X chromosome, a mutation on one X chromosome may be made up for with a normal gene on the other; males with a mutation on their X chromosome are more likely to actually show a sex-linked trait since they do not have a second X chromosome. Most traits that are sex-linked are on the X chromosome.

Test Cross: a cross of an individual of uncertain genotype for a gene or genes under study to one known to be homozygous for the recessive allele of that gene(s). Testcrosses are used to determine the genotype of an individual displaying the phenotype associated with the dominant allele of one or more genes. Testcrosses are also used to determine whether two genes are sorting independently, and if they are not, testcrosses allow the measurement of the map distance between genes.

Trait: a characteristic or feature of an organism, also called its phenotype. Traits might be easily visible, like hair color, presence or absence of wings, or leaf shape. Traits can also be less easy to see, like a tendency to get a certain disease. Traits can be determined by genes or the environment, or more commonly by the interactions between them.

Transcription: production of mRNA from a DNA sequence.

Translation: production of a protein from an mRNA sequence. DNA→transcribed into RNA→translated into Protein; so remember that alphabetically transcription comes before translation.

True-breeding: a kind of breeding in which the parents with a particular phenotype produce offspring only with the same phenotype.

Wild Type: the form of a trait most commonly found in nature; Also, The most common allele for a particular gene in a population of organisms. For example, in the wild most mice are agouti (a shade of brown). Pure white or black mice have been bred in laboratories for specific purposes, and are less often found in nature.

X Chromosome: one of the two chromosomes involved in sex determination in mammals. XX mammals are female; XY mammals are male. (Sex determination in the drakes of Geniverse is modeled after mammals.)

X-Linked: traits that are determined by genes on the X or Y chromosome. Since females have two copies of the X chromosome, a mutation on one X chromosome may be made up for with a normal gene on the other; males with a mutation on their X chromosome are more likely to actually show a sex-linked trait since they do not have a second X chromosome. Most traits that are sex-linked are on the X chromosome.

Y Chromosome: one of the two chromosomes involved in sex determination in most mammals. XY mammals are male. (Sex determination in the drakes of Geniverse organisms is modeled after mammals.)