23.1 Mendel’s Laws. Gregor Mendel Augustinian Monk Around 1857, began breeding garden peas to study inheritance. Performed crosses between true breeding lines of garden peas that differed in a single trait. Pea plants have several advantages for genetics:
Stigma (receives pollen)
Ovules (produce female gametes)
1. Remove anthers
from one plant.
2. Collect pollen
from a different plant.
3. Transfer pollen
to a stigma of the
anthers have been
When Mendel allowed the F1 plants to self-fertilize, the F2 generation included both purple-flowered and white-flowered plants.
1. Different factors or alternative versions of genes (alleles) account for variations in inherited characters.
of the alternate (recessive) allele
A homozygous man with a widow’s peak X a woman with a straight hairline
Two individuals who are both Ww
The Law of Independent Assortment:
¾ X ¾ = 9/16
¾ X ¼ = 3/16
¼ X ¾ = 3/16
¼ X ¼ = 1/16
Example: If an individual in the third generation lacks a widow’s peak, but both her parents have widow’s peaks, then her parents must be heterozygous for that gene.
A IAIA or IAi
B IBIB or IBi
XBXB female with normal color vision
XBXb carrier female with normal color vision
XbXb colorblind female
XBY male with normal color vision
XbY colorblind male