Laying Foundations: Peas, Patterns, and Probabilities (Section 17.1)

Selective Breeding

Choosing and breeding specific plants and animals for desired physical features or behaviours

True Breeding

Organisms that are homozygous for a particular trait or set of traits and produce offspring that exhibit the same characteristics generation after generation

Monohybrid Cross

A cross of two individuals in which only one trait is different

Dominant

A trait which always appears (is expressed) in an individual that is either heterozygous (Aa) or homozygous (AA) for that trait

Recessive

A trait that doesn’t appear (is not expressed) in an individual that is heterozygous (Aa) for that trait

Complete Dominance

A condition in which the dominant allele of a gene completely conceals the presence of the recessive allele of a gene

An individual with one recessive and one dominant allele has the same observable physical characteristic as an individual with two dominant alleles

Law of Segregation

Mendel’s first law of inheritance, stating that all individuals have two copies of each gene

These copies segregate randomly during gamete formation, and each gamete receives one copy of every gene

Genotype

The combination of alleles for any given trait

Phenotype

The visible physical and physiological traits of an organism

Homozygous

Describes an individual with two identical alleles for a trait (AA or aa)

Heterozygous

Describes an individual with two different alleles for a trait (Aa)

Punnett Square

Simple grid used to illustrate all possible combinations of simple genetic crosses

Test Cross

Cross of an individual of unknown genotype with a homozygous recessive individual

Used as a method to determine the unknown genotype

Dihybrid Cross

Cross of two individuals that differ in two traits

Law of Independent Assortment

Mendel’s second law of inheritance, stating that the two alleles for one gene segregate independently of the alleles for other genes during gamete formation

Incomplete Dominance

A condition in which neither of two alleles for the same gene can completely conceal the presence I’d the other

Co-Dominance

Described a situation in which two alleles may be expressed equally

Occurs when two different alleles for a trait are both dominant

Chromosome Theory of Inheritance

Theory proposed by Walter Sutton that genes are carried in chromosomes