Chapter 11 Vocab

Genetics

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

True-breeding

A true breeding organism, sometimes also called a pure-bred, is an organism having certain biological traits which are passed on to all subsequent generations when bred with another true breeding organism for the same traits. In other words, to "breed true" means that two organisms with a particular, heritable phenotype produce only offspring with that (same) phenotype.

Trait

A genetically determined characteristic or condition: a recessive trait.

Hybrid

The offspring of genetically dissimilar parents or stock, especially the offspring produced by breeding plants or animals of different varieties, species, or races.

Gene

The basic physical unit of heredity; a linear sequence of nucleotides along a segment of DNA that provides the coded instructions for synthesis of RNA, which, when translated into protein, leads to the expression of hereditary character.

Allele

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

Segregation

The separation of allelic genes into different gametes during meiosis.

Gamete

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

Probability

The quality or fact of being probable.

Punnett Square

The Punnett square is a diagram designed by Reginald Punnett and used by biologists to determine the probability of an offspring having a particular genotype.

Homozygous

Having identical pairs of genes for any given pair of hereditary characteristics.

Heterozygous

Having dissimilar pairs of genes for any hereditary characteristic.

Phenotype

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

Genotype

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.

Homologous

Having the same alleles or genes in the same order of arrangement: homologous chromosomes.

Diploid

Having two similar complements of chromosomes.

Haploid

Pertaining to a single set of chromosomes.

Meiosis

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.

Tetrad

A group of four chromatids formed by synapsis at the beginning of meiosis.

Crossing Over

The exchange of genetic material between homologous chromosomes that occurs during meiosis and contributes to genetic variability.

Gene Map

A graphic representation of the arrangement of genes or DNA sequences on a chromosome.