Heredity and Gregor Mendel's Principles of Genetics

Gene

It is the sequence of DNA that codes for a protein and determining a trait.

Alleles

The different forms of a single gene.

Dominant allele

Whose appearance dominates over other alleles for the same trait.

Recessive allele

That does not show when a dominant allele is present.

Homozygous

Has two identical alleles for a gene (true-breeding).

Heterozygous

Has two different alleles for a gene (hybrid).

Genotype

Gene pair for a trait.

Phenotype

The observable physical characteristics (appearance) of an allele pair.

P generation

Parental generation.

F1 generation

Offspring from P generation.

F2 generation

Offspring from F1 generation.

Law of Segregation

Alleles separate from each other when gametes form in meiosis.

Law of Independent Assortment

Alleles for different genes usually separate independently of each other.

True-breeding

Organisms that produce offspring identical to themselves.

Hybrid

Offspring resulting from the cross of two true-breeding plants.

Cross-Pollination

When Mendel cross-pollinated two true-breeding plants with different traits.

Phenotype of purple flower

Purple flower.

Genotype if purple is dominant

PP or Pp.

Genotype if it is a recessive trait

pp.

Mendel's conclusion about inheritance

Inheritance is determined by 'factors' (now called genes) that are passed down from parent to offspring.

Proportion of F2 offspring that were yellow

1/4.

Proportion of F2 offspring that were green

3/4.

Example of allele trait abbreviation

T = tall, t = short.