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| A qualitative characteristic; a discrete attribute as contrasted with metrical character. A trait is amenable to segregation rather than quantitative analysis; it is an attribute of phenotype, not of genotype. |
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| The fundamental, physical, and functional unit of heredity. It is because a gene is a segment of DNA (on a specific site on a chromosome) that is responsible for the physical and inheritable characteristics of an organism. |
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| One member of a pair (or any of the series) of genes occupying a specific spot on a chromosome (called locus) that controls the same trait. For example, a pair of alleles controlling the same trait, i.e. eye color: one allele codes for blue eyes, another allele for brown eyes. |
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| The property of a gene (or allele) when it suppresses the expression, or dominates the effects, of the recessive gene (or allele). Usually, a dominant allele is symbolized with a capital letter and the recessive allele a small letter, for example: Hh |
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| A gene (or allele) whose phenotypic expression is masked by a dominant gene (or allele). The recessive trait may be expressed when the recessive genes are in homozygous condition or when the dominant gene is not present. That happens when an organism inherits a pair of recessive genes from its parents. |
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| A kind of dominance occurring in heterozygotes in which the dominant allele is only partially expressed, and usually resulting in an offspring with an intermediate phenotype. Synonym: partial dominance. |
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| The physical appearance or biochemical characteristic of an organism as a result of the interaction of its genotype and the environment, for example, skin color or height. |
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A set of alleles that determines the expression of a particular characteristic or trait (phenotype).
genotype + environment + random variation → phenotype |
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| A condition in which a characteristic that apparently manifests more frequently in one sex than in the other is associated with the gene(s) located in the sex chromosome. |
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| A genetic cross between homozygous individuals but with different alleles for a single gene locus of interest. Monohybrid cross is one of the methods used by the geneticist, Gregor Mendel, in his garden peas experiments. |
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| A genetic cross between individuals with different alleles for two gene loci of interest. Was used to formulate his Law of Independent Assortment. |
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| A tool that helps to show all possible allelic combinations of gametes in a cross of parents with known genotypes in order to predict the probability of their offspring possessing certain sets of alleles. Named after Reginald Punnett ,a British geneticist, who developed it. |
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| In a pair of alleles, one trait may cover up the allele of the other trait; for example; brown eyes are dominant to blue eyes. |
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| Only one of the two possible alleles from each parent passed on to the offspring from each parent, so that during meiosis, the haploid number ensures that hall the sex cells get one allele and half get the other. |
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| Law of independent assortment |
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| Alleles sort independently of each other so that many combinations are possible depending on which sperm ends up with which egg. |
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| Reproduction that involves the fusion of gametes or haploid reproductive cells. Two gametes, one of each sex, fuse during fertilization to produce a zygote. |
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| Occurring without a fusion of gametes and by which offspring arise from a single parent, and inherit the genes of that parent only. |
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| (1) a change in the structure of a nucleotide sequence, often, but not necessarily, in a gene; (2) the altered sequence or gene resulting from such a change; (3) a change in the karyotype (chromosomal mutation) (4) an individual or type having such a change in its genetic makeup, and any descendants of that individual that in which it also occurs. |
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| The creation of a duplicate molecule from a template. During the replication of DNA the two strands of a duplex DNA molecule are first unzipped, then each of the separated ("parental") strands is used as a template for the synthesis of a new strand. |
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| deoxyribonucleic acid (DNA) |
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| The molecule in living organisms that contains inherited information; it is made up of genes which in turn make up the chromosomes. |
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| The production of new forms of life over time, as documented in the fossil record. |
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| A natural evolutionary process in which different heritable traits have a differential effect on the ability to produce offspring. Since there are variations due to sexual reproduction and mutations, some traits allow for better survival rates. |
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| Certain factors increase chances of variability in populations which lead to evolution such as mutations, sexual reproduction, immigration, large populations and variation in geographic local. |
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| 1) a genetic process whereby a population or at type of organism is thought to have become better suited to its environment; (2) a trait considered to be the product of such a process. |
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| The evolutionary process by which new biological species arise which can no longer exchange genes with the original population. |
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| The end of an organism or of a group of organisms (taxon), normally a species. Species become extinct when they are no longer able to survive in changing conditions or against superior competition. |
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