Genetic Terms Part 1
Heredity - the transmission of traits from parents to offspring.
Environment – all outside forces, everything that an organism comes in contact with.
Genetics – the science of heredity.
Dominance – when one allele of a gene prevents the expression of another.
Recessive – when one allele of a gene is masked when a dominant allele is present.
Hybrid – offspring of parents differing in one or more traits.
Principle of Segregation – a pair of factors (alleles of a gene) are segregated, or separated, during the formation of gametes.
Principle of Independent Assortment – alleles of a genes are separated and distributed to gametes independent of other genes.
Walter Sutton – chromosome theory – genes are located on chromosomes.
Genotype - the genetic make-up of an organism, the alleles of the genes that it has, represented by letters like BB, Bb, bb, BbAA etc…
Phenotype – the outward appearance of an organism as the result of its genotype. (brown, blue, tall, short)
Homozygous – (true-breeder, pure) organism in which the paired alleles for a specific gene are identical. Represented by letters like bb, BB, bbAA etc ….
Heterozygous – organisms in which the paired alleles for a specific gene are not identical. Represented by letters like Bb, Aa, BbDd etc….
Allele – forms of a gene responsible for contrasting traits. Two or more alternate forms of a gene
Punnett Square – a grid system used to find possible genotypes of offspring.
Monohybrid Cross – a cross involving one gene of the parents. The alleles could differ.
Dihybrid Cross – a cross involving two gene of the parents. The alleles could differ.
Incomplete Dominance – when two different alleles of the same gene affect the phenotype, the heterozygous condition will be a third intermediate phenotype.
Codominance - when two different alleles of the same gene affect the phenotype, in the heterozygous condition both alleles each affect the phenotype in separate distinguishable ways.
Mitosis – the division of the chromosomes preceding the division of the cytoplasm. Mitosis produces cells for growth, maintenance, repair and asexual reproduction.
Meiosis – reduces a diploid cell to four haploids, for the production of gametes, the number of chromosomes is reduced to half.
Gene – basic unit of heredity, a portion of DNA that codes for a protein of functional RNAs.
Homologous Chromosome – one of two members of a pair of characteristically similar chromosomes.
Male chromosomes – XY Female chromosomes – XX
Genetic Terms Part 2
P generation – the first mating pair
F1 generation – offspring of the P generation
F2 generation – offspring of the F1 generation when allowed to interbreed
Probability – the likelihood that a specific event will occur, can be expressed in three ways 1) percentage, 2) fraction, 3) ratio
True-breeding – when self-pollinated produce the same phenotype generation after generation. They are Homozygous
Multiplication rule – when two separate events occur simultaneously multiply the probability of one event with the probability of the other.
Addition rule – the probability that any one of two or more mutually exclusive events will occur is calculated by adding their individual probabilities.
Pleiotropy – when a gene has multiple phenotypic effects
Epistasis – when the phenotypic expression of a gene at one locus alters the expression of a gene at a second locus.
Locus – the position of a gene on a chromosome.
Quantitative characters – characters that vary in a population along a continuum (skin color).
Polygenic inheritance – the additive effect of two or more genes on a single phenotype
Multifactorial – many factors both genetic and environmental, collectively influencing phenotype