Biology - Ch. 12 - Patterns of Inheritance

The study of traits that are transmitted from one generation of living things to the next. p1 = first parent generation f1=first offspring generation p2=second parent generation f2=second offspring generation

The branchy of heredity that attempts to explain how the similarities and diffrerences between parents and offspring are inherited.

Founder of modern genetics; observed patterns of inheritance in peas that provided clues about what the genes were doing.

Studied generations of garden peas and formulated simple mathematical expressions to explain patterns of heredity.

Breed "true-breeding" varieties which all display the same form of a trait (e.g. white flowers)

Human manipulation of the pollen introduced genetic variation in "hybrids".

one trait crosses (f2)- Mendel crossed pure parents of contrasting characters and all the f1 offspring showed only one of the characteristics. conclusion: in an individual, every trait is controlled by a pair of factors; one of the factors can be dominant (show up) over the other, which is recessive (hidden).

one-trait crosses (f2) - mendel crossed two hybrids and the recessive characters, which were hidden in the f1, showed presence in the 1/4 of the f2 offspring. conclusion: the factors (homologues) seperate when the gametes are formed and onlny one factor of each pair is present in each gamete.

The principle for two trait crosses

two trait crosses: mendel crossed true-breeding parents with contrasting traits for flower color and plant height and found that all four factors showed up in a 9:3:3:1 ration in the second generation. conclusion: pairs of factors seperate independently of one another to form gametes, and therefore all possible combos of factors may occur in the gametes.

Instructions for producing a trait

Location of a gene on a chromosome

Have two genes (a gene pair) for each trait - each on a homologous chromosome.

Various molecular forms of a gene for the same trait.

Both alleles are the same.