Mendelian Genetics

allele

allele

alternative form of a gene (one member of a pair) located at a specific position on a specific chromosome (a letter)

dihybrid cross

a two-trait cross (ex. color & shape)

dominant allele

an allele that produces the same phenotype whether its paired allele is identical or different (capital letter)

F1 generation

first filial generation is the generation resulting immediately from a cross of the first set of parents (P generation)

F2 generation

second filial generation is the generation resulting from a cross between two F1 individuals

fertilization

a process in sexual reproduction in which a sperm unites with an egg to make the first cell of a new organism, or zygote

gene

sequence of DNA that codes for a protein and thus determines a trait

genetics

the study of heredity

genome

the entire "library" of genetic instructions in DNA that an organism inherits

genotype

the combination of alleles located on homologous chromosomes that determines a specific characteristic or trait (the allelic combination such as Bb)

Gregor Mendel

father of genetics

heredity

the passing of traits from one generation to the next

heterozygous

term used to refer to an organism that has two different alleles for the same trait (ex. Bb)

homozygous

term used to refer to an organism that has two identical alleles for the same trait (ex. BB or bb)

hybrid

offspring that are the result of mating between two genetically different kinds of parents; opposite of purebred

Law of Independent Assortment

states that genes for different traits (LOCATED ON DIFFERENT CHROMOSOMES) can segregate independently during the formation of gametes

Law of Segregation

states that allele pairs (for a gene) separate, or segregate, during gamete formation (You receive one copy from each parent)

meiosis

a type of cell division that results in four genetically different daughter cells each with half the number of chromosomes of the parent cell (also known as reduction division)

monohybrid cross

a one-trait cross (ex. color)

non-Mendelian inheritance

refers to any pattern of inheritance in which traits do not segregate in accordance with Mendel's laws (ex. incomplete dominance, codominance, multiple alleles, polygenic traits, sex-linked traits)

P generation

parental generation is the first generation involving two individuals that are mated to predict or analyze the genotypes of their offspring

phenotype

the observable physical or biochemical characteristics of an organism, as determined by the genotype (the expressed trait such as brown eyes)

Principle of Dominance

when individuals with contrasting traits are crossed, the offspring will express only the dominant trait

probability

the possibility of different outcomes (percentage or ratio)

Punnett square

diagram showing the gene combinations that might result from a genetic cross

purebred

offspring that are the result of mating between genetically similar kinds of parents; opposite of hybrid; same as true breeding

recessive allele

an allele that produces its characteristic phenotype only when its paired allele is identical (lowercase letter)

sexual reproduction

process by which two cells from different parent unite to produce the first cell of a new organism

trait

a specific characteristic that varies from one individual to another