Science

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Heredity

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The genetic transmission of characteristics from parent to offspring

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Genetics

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the science of heredity, dealing with resemblances and differences of related organisms resulting from the interaction of their genes and the environment

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Trait

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A genetically determined characteristic or condition

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Gamete

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a mature sexual reproductive cell, as a sperm or egg, that unites with another cell to form a new organism

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Pollination

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the transfer of pollen from the anther to the stigma

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Fertilization

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The union of male and female gametes to form a zygote

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Hybrid

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produced by crossbreeding

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Allele

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any of several forms of a gene, usually arising through mutation, that are responsible for hereditary variation

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Dominant

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the one of a pair of alternative alleles that masks the effect of the other when both are present in the same cell or organism

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Recessive

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that one of a pair of alternative alleles whose effect is masked by the activity of the second when both are present in the same cell or organism

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Law of Segregation

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the principle, originated by Gregor Mendel, stating that during the production of gametes the two copies of each hereditary factor segregate so that offspring acquire one factor from each parent

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Phenotype

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the appearance of an organism resulting from the interaction of the genotype and the environment

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Genotype

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the genetic makeup of an organism or group of organisms with reference to a single trait, set of traits, or an entire complex of traits.

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Homozygous

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having identical pairs of genes for any given pair of hereditary characteristics

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Heterozygous

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having dissimilar pairs of genes for any hereditary characteristic

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Law of Independent Assortment

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the principle, originated by Gregor Mendel, stating that when two or more characteristics are inherited, individual hereditary factors assort independently during gamete production, giving different traits an equal opportunity of occurring together.

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Diploid

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having two similar complements of chromosomes

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Haploid

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pertaining to a single set of chromosomes

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Homologous Chromosome

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one of a pair of chromosomes that match up at meiosis and are identical in morphology and arrangement; a chromosome with the same gene sequence as another, each derived from one parent

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Meiosis

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part of the process of gamete formation, consisting of chromosome conjugation and two cell divisions, in the course of which the diploid chromosome number becomes reduced to the haploid

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Sperm

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a male reproductive cell/gamete

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Egg

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A female gamete

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Zygote

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the cell produced by the union of two gametes, before it undergoes cleavage

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Sexual Reproduction

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reproduction involving the union of gametes

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Crossing Over

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the interchange of corresponding chromatid segments of homologous chromosomes with their linked genes

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Genetic Recombination

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is the process by which a strand of DNA is broken and then joined to the end of a different DNA molecule

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Nondisjunction

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the failure of chromosomes to separate and segregate into daughter cells at division

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Nitrogen Base

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A basic compound that contains nitrogen, such as a purine or pyrimidine

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Double Helix

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the spiral arrangement of the two complementary strands of DNA

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DNA Replication

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is the process of copying a double-stranded DNA molecule

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mutation

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a sudden departure from the parent type in one or more heritable characteristics, caused by a change in a gene or a chromosome

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variation

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a difference or deviation in structure or character from others of the same species or group

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purebred

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bred for many generations from member of a recognized breed or strain

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messenger RNA

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a difference or deviation in structure or character from others of the same species or group

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ribosomal RNA

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a type of RNA, distinguished by its length and abundance, functioning in protein synthesis as a component of ribosomes

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transfer RNA

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a small RNA molecule, consisting of a strand of nucleotides folded into a clover-leaf shape, that picks up an unattached amino acid within the cell cytoplasm and conveys it to the ribosome for protein synthesis

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transcription

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the process by which genetic information on a strand of DNA is used to synthesize a strand of complementary RNA

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codon

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a triplet of adjacent nucleotides in the messenger RNA chain that codes for a specific amino acid in the synthesis of a protein molecule

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translation

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the process by which a messenger RNA molecule specifies the linear sequence of amino acids on a ribosome for protein synthesis

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Pedigree

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a genealogical table, chart, list, or record, esp. of a purebred animal

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Incomplete Dominance

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the appearance in a heterozygote of a trait that is intermediate between either of the trait's homozygous phenotypes

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Codominant alleles

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A type of inheritance in which heterozygotes fully express both alleles

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multiple alleles

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a series of three or more alternative or allelic forms of a gene, only two of which can exist in any normal, diploid individual.

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autosome

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any chromosome other than a sex chromosome

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sex chromosome

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a chromosome, differing in shape or function from other chromosomes, that determines the sex of an individual

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sex-linked trait

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A trait associated with a gene that is carried only by the male or female parent.

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polygenic inheritance

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the heredity of complex characters that are determined by a large number of genes, each one usually having a relatively small effect