CONCEPT 14.1: Mendel used the scientific approach to identify two
laws of inheritance
Mendel discovered the basic principles of heredity by breeding garden peas in carefully planned
experiments.
Mendel’s Experimental, Quantitative Approach
Mendel’s fresh approach to studying heredity allowed him to deduce principles that had
remained elusive to others.
A character is a heritable feature that varies among individuals (such as flower color).
Each variant for a character, such as purple or white color for flowers, is called a trait.
Peas were available to Mendel in wide different varieties.
Other advantages of using peas
-Short generation time
-Large numbers of offspring
-Mating could be controlled; plants could be allowed to self-pollinate or could be cross-
pollinated
, Mendel chose to track only those characters that occurred in two distinct alternative
forms.
He also started with varieties that were true-breeding (plants that produce offspring of
the same type when they self-pollinate)
In a typical experiment, Mendel mated two contrasting, true-breeding varieties, a process
called hybridization.
The true-breeding parents are called the P generation
The hybrid offspring of the P generation is called the F1 generation
When F1 individuals self-pollinate or cross-pollinate with other F1 hybrids, the F2
generation is produced
The Law of Segregation
-In the 1800s, the explanation of heredity was the “blending” hypothesis
-When Mendel crossed contrasting, true-breeding white- and purple-flowered pea plants, all of
the F1 hybrids were purple
-The blending hypothesis did not predict this result
-When Mendel crossed the F1 hybrids, many F2 plants had purple flowers, but some had white.
-Mendel discovered a ratio of about three purple flowers to one white flower in the F2 generation.
-Mendel reasoned that only the purple flower factor affected flower color in the F1 hybrids.
laws of inheritance
Mendel discovered the basic principles of heredity by breeding garden peas in carefully planned
experiments.
Mendel’s Experimental, Quantitative Approach
Mendel’s fresh approach to studying heredity allowed him to deduce principles that had
remained elusive to others.
A character is a heritable feature that varies among individuals (such as flower color).
Each variant for a character, such as purple or white color for flowers, is called a trait.
Peas were available to Mendel in wide different varieties.
Other advantages of using peas
-Short generation time
-Large numbers of offspring
-Mating could be controlled; plants could be allowed to self-pollinate or could be cross-
pollinated
, Mendel chose to track only those characters that occurred in two distinct alternative
forms.
He also started with varieties that were true-breeding (plants that produce offspring of
the same type when they self-pollinate)
In a typical experiment, Mendel mated two contrasting, true-breeding varieties, a process
called hybridization.
The true-breeding parents are called the P generation
The hybrid offspring of the P generation is called the F1 generation
When F1 individuals self-pollinate or cross-pollinate with other F1 hybrids, the F2
generation is produced
The Law of Segregation
-In the 1800s, the explanation of heredity was the “blending” hypothesis
-When Mendel crossed contrasting, true-breeding white- and purple-flowered pea plants, all of
the F1 hybrids were purple
-The blending hypothesis did not predict this result
-When Mendel crossed the F1 hybrids, many F2 plants had purple flowers, but some had white.
-Mendel discovered a ratio of about three purple flowers to one white flower in the F2 generation.
-Mendel reasoned that only the purple flower factor affected flower color in the F1 hybrids.
