6.3 Mendel and Heredity

KEY CONCEPT Mendel’s research showed that traits are inherited as discrete units, we now call what??????

Jeans?Not those jeans,GENES!!!!!!

6.3 Mendel and Heredity

Mendel laid the groundwork for genetics. (On Your Own)

• Traits are distinguishing characteristics that are inherited.

• Genetics is the study of biological inheritance patterns and variation.

• Gregor Mendel showed that traits are inherited as discrete units.

• He is called the “Father of Genetics”

• Many in Mendel’s day thought traits were blended.

6.3 Mendel and Heredity

Mendel’s data revealed patterns of inheritance. (P Notes)

• Mendel made three key choices in his experiments.– use of purebred plants– control over breeding– observation of seven

“either-or” characteristics

6.3 Mendel and Heredity

Mendel’s data revealed patterns of inheritance. (On Your Own)Mendel chose pea plants because:• they reproduce quickly • they contain both male and

female reproductive organs in their flowers (self-pollinate)

• he could control their mating

Purebred plants are those that have self-pollinated over a long enough period of time to allow for a genetically uniform lineage.

6.3 Mendel and Heredity

• Mendel used pollen to fertilize selected pea plants. (On Your Own)

Mendel controlled thefertilization of his pea plantsby removing the male parts,or stamens.

He then fertilized the femalepart, or pistil, with pollen froma different pea plant.

– P (parent) generation crossed to produce F1 generation (first offspring)

– He controlled the self-pollination process by removing male flower parts (stamens)

– Once they were removed, he fertilized the female part (pistil)

6.3 Mendel and Heredity

Characteristics Chosen by Mendel (P Notes)

• Mendel chose seven traits to follow during his pea experiment:

1. Pea shape

2. Pea color

3. Pod shape

4. Pod color

5. Plant height

6. Flower color

7. Flower position

They are ALL either-or characteristics: tall or short, peas are wrinkled or round, etc.

6.3 Mendel and Heredity

Understanding Genetics (On Your Own)In genetics, the mating of two organisms is called a cross.

Example: Mendel crossed a purebred white-flowered pea plant with a purebred purple-flowered pea plant.

These parental plants are called the P generation, and represented by a P.

The offspring from this first parental cross are called the first filial or F1 generation.

All of this F1 generation had purple flowers.

The trait for white flowers was not evident.

Mendel then allowed the F1 generation to self-pollinate without interfering with the process.

The resulting F2 generation produced both purple and white flowers.

This showed him that the white trait has only been masked.

Let’s take a look at them.

6.3 Mendel and Heredity

• Mendel allowed the resulting plants to self-pollinate. (On Own)

– Among the F1 generation, all plants had purple flowers

– F1 plants are all heterozygous (different)

– Among the F2 generation, some plants had purple flowers and some had white

6.3 Mendel and Heredity

Mendel’s Observations (P Notes)

• After crossing many pea plants, Mendel observed:– Each cross yielded or produced similar ratios in the F2

generation– About ¾ of the plants had purple flowers– About ¼ of the plants had white flowers– This is displayed as a ration of 3:1 of purple to white

6.3 Mendel and Heredity

• Mendel observed pea plant characteristics or patterns in the first and second generations of his crosses.

6.3 Mendel and Heredity

Cross: the mating of two organisms (On Your Own)Mendel mated purebred pea plants with purple flowers with purebred plants with white flowers

• P: the parental generation; Mendel used purebred plants for the P generation

Example: he crossbred plants with purple flowers with purebred plants with white flowers.

• F1: the first generation of offspring resulting from the parental cross

Example: Mendel’s F1 plants all had purple flowers; Mendel allowed this generation to self-pollinate

• F2: the secondary generation: the result of the self-pollination of F1 plants

Example: In Mendel’s F2 generation, ¾ had purple flowers and ¼ had white flowers.

6.3 Mendel and Heredity

Results: (P Notes)

• For all seven traits, Mendel found that approximately ¾ of F2 offspring had one trait and ¼ of the offspring had the other trait.

6.3 Mendel and Heredity

• Mendel drew three important conclusions. (P Notes)

– Traits are inherited as discrete units.– The last two conclusions are

called the law of segregation.• Organisms inherit two copies of each

gene, one from each parent.• The two copies segregate

during gamete formation. purple white