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unit heredity
Term | Definition |
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dna | deoxyribonucleic acid, a self-replicating material present in nearly all living organisms as the main constituent of chromosomes. It is the carrier of genetic information |
chromosomes | a threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes. |
cell cycle | series of events that take place in a cell leading to its division and duplication of its DNA (DNA replication) to produce two daughter cells. In bacteria, which lack a cell nucleus, the cell cycle is divided into the B, C, and D periods. |
interphase | the resting phase between successive mitotic divisions of a cell, or between the first and second divisions of meiosis. |
mitosis | a type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus, typical of ordinary tissue growth. |
cytokinesis | the cytoplasmic division of a cell at the end of mitosis or meiosis, bringing about the separation into two daughter cells. |
homologous chromosomes | pairs, one from each parent, that are similar in length, gene position, and centromere location. The position of the genes on each homologous chromosome is the same, however the genes may contain different alleles. |
meiosis | a type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell, as in the production of gametes and plant spores. |
asexual reproduction | by which offspring arise from a single organism, and inherit the genes of that parent only; it does not involve the fusion of gametes, and almost never changes the number of chromosomes. |
sexual reproduction | the production of new living organisms by combining genetic information from two individuals of different types (sexes). In most higher organisms, one sex (male) produces a small motile gamete that travels to fuse with a larger stationary gamete produced |
fertilization | the action or process of fertilizing an egg, female animal, or plant, involving the fusion of male and female gametes to form a zygote. |
heredity | the passing on of physical or mental characteristics genetically from one generation to another. |
gene | a unit of heredity that is transferred from a parent to offspring and is held to determine some characteristic of the offspring. |
allele | one of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome. |
genotype | the genetic constitution of an individual organism. |
phenotype | the set of observable characteristics of an individual resulting from the interaction of its genotype with the environment. |
dominant | An allele or a gene that is expressed in an organism's phenotype, masking the effect of the recessive allele or gene when present. (2) (Of, or pertaining to) An organism that expresses the dominant gene (or allele). |
recessive | gene or allele is one in which the effect is not tangible, or is masked by the effects of the dominant gene. The recessive trait may be expressed when the recessive genes are in homozygous condition or when the dominant gene is not present. |
incomplete dominance | a form of intermediate inheritance in which one allele for a specific trait is not completely expressed over its paired allele. This results in a third phenotype in which the expressed physical trait is a combination of the phenotypes of both alleles. |
codominance | A form of dominance in which the alleles of a gene pair in a heterozygote are fully expressed thereby resulting in offspring with a phenotype that is neither dominant nor recessive. Supplement. ... A typical example showing codominance is the ABO blood gr |
punnet square | a diagram that is used to predict an outcome of a particular cross or breeding experiment. It is named after Reginald C. Punnett, who devised the approach. The diagram is used by biologists to determine the probability of an offspring having a particular |
ratio | describes the number of times a genotype would appear in the offspring after a test cross. For example, a test cross between two organisms with same genotype, Rr, for a heterozygous dominant trait will result in offspring with genotypes: RR, Rr, and rr. . |
probability | he likelihood of an event to occur. Supplement. Probability is used to measure the chances or likelihood of an event to occur, a hypothesis being correct, or a scientific prediction being true. In biology, it is used in predicting the outcome of a genetic |
pedigree | An ancestral line or chart depicting the lineage or descent of an individual. (2) (genetics) A diagram showing the lineage or genealogy of an individual and all the direct ancestors, usually to analyze or follow the inheritance of trait. |