Inheritance Vocabulary

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Dominant Allele

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An allele that expresses its phenotypic effect even when heterozygous with a recessive allele

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Recessive Allele

Back 2

An allele that produces its characteristic phenotype only when its paired allele is identical

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Punnett Square

Back 3

A diagram that is used to predict an outcome of a particular cross or breeding experiment

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Test Cross

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A genetic cross between a homozygous recessive individual and suspected heterozygote to determine the genotype of the unknown parent

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Crossing Over

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The exchange of genes between homologous chromosomes, resulting in a mixture of parental characteristics in offspring.

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Karyotype

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The number and visual appearance of the chromosomes in the cell nuclei of an organism or species.

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Heterozygous

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Having two different alleles for a single trait.

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Homozygous

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Having two of the same alleles for a single trait.

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Gamete

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A mature haploid male or female germ cell that is able to unite with another of the opposite sex in sexual reproduction to form a zygote.

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Allele

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One of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome.

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Gene

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A unit of heredity that is transferred from a parent to offspring and is held to determine some characteristic of the offspring.

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Meiosis

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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.

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Dihybrid Cross

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A cross between two different alleles that differ in two observed traits. Mendelian inheritance: relationship of completely dominant or completely recessive.

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Monohybrid Cross

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A monohybrid cross is a mating between two individuals with different alleles at one genetic locus of interest. The character(s) being studied in a monohybrid cross are governed by two or multiple alleles for a single locus. (Completely dominant or completely recessive.)

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Chromosome

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A threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.

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Gregor Mendel

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Augustinian monk and botanist whose experiments in breeding garden peas led to his eventual recognition as founder of the science of genetics (1822-1884)

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Chromatid

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Each of the two threadlike strands into which a chromosome divides longitudinally during cell division. Each contains a double helix of DNA.

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Centromere

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The point on a chromosome by which it is attached to a spindle fiber during cell division.

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Spindle Fiber

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A protein structure that divides the genetic material in a cell. It is necessary to equally divide the chromosomes in a parental cell into two daughter cells during both types of nuclear division: mitosis and meiosis

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Pedigree

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A genetic representation of a family tree that diagrams the inheritance of a trait or disease though several generations.

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Autosomal Inheritance

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Pertaining to a chromosome that is not a sex chromosome.

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X-Linked Inheritance

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A mode of genetic inheritance by which a dominant or recessive gene is carried on the X chromosome.

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Genetic Drift

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Gene Flow

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Variation in the relative frequency of different genotypes in a small population, owing to the chance disappearance of particular genes as individuals die or do not reproduce.

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DNA Fingerprinting

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The analysis of DNA from samples of body tissues or fluids in order to identify individuals.

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Genetic Cloning

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Process in which a gene of interest is located and copied (cloned) out of DNA extracted from an organism.

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Genetic Engineering

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The deliberate modification of the characteristics of an organism by manipulating its genetic material.

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Selective Breeding

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The process of selecting particular phenotypic traits (characteristics) by choosing which animal or plant males and females will sexually reproduce and have offspring together.

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Translocation

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A chromosome abnormality caused by rearrangement of parts between non-homologous chromosomes

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Nondisjunction

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The failure of one or more pairs of homologous chromosomes or sister chromatids to separate normally during nuclear division

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Complete Dominance

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The dominant allele completely masks the effect of the allele that is recessive

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Incomplete Dominance

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The dominant allele incompletely masks the effect of the allele that is recessive, resulting in a blended phenotype

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Codominance

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Neither allele is dominant over the other; both alleles of a gene pair in a heterozygote are fully expressed.