Gregor Mendel In the 1850’s he experimented with thousands of pea plants and formed the foundation for genetics. He is called the Father of Genetics. Why did he study pea plants? The traits were in two forms only. The pea plants produced lots of offspring and made it easy to collect lots of data.

3. Height in Pea Plants Tall Short TT Tall Short Tall Tall Tall Tall Tall Short TT tt Tt Tt TT Tt Tt tt Tall Short TT

4. Pg. 118 Traits of Pea Plant that Mendel studied. Along stem At tip smooth bumpy tall short

5. Recessive alleles will show up as a trait when there are two recessive alleles or there is no dominant allele. The only way to have a short pea plant is to get the recessive short allele from both parents. T= Tall t = short T t T t TT Tt tt

6. Mendel presented his results on heredity in 1866 to science. Some scientists thought that he had made heredity too simple. Because there were no cell phones, televisions, radios, or computers, many did not hear about his work. His work was forgotten for 34 years. In 1900, three scientists rediscovered his work and made it known that Mendel was correct about the process of heredity. That is why he is called the Father of Genetics.

Mendel and His Peas Pages 115-117 1. What is a self-pollinating plant? – pg. 115 Has both male and female reproductive structures 2. What takes place in pollination? Pg. 115 - Figure 2. Pollen from the anthers (male) is transferred to the stigma (female). The pollen fertilizes the eggs in the ovary. 3. Why was it important to Mendel that pea plants were self- pollinating? Pg. 115 Mendel was able to grow true-breeding plants or homozygous plants. This way he knew what traits to expect. When a true-breeding pea plant self-pollinates, all of its offspring will have the same trait as the parent pea plant.

Mutualism – because the bee and the flower both benefit 4. Pea plants can also cross-pollinate. What is cross- pollination? Pollen from one plant fertilizes the ovule of a flower on a different pea plant. 5. In cross-pollination, pollen may be carried by insects or wind to the flower of a different pea plant. 6. When an insect such as a bee is feeding on pollen, some gets on its wings or feet. Then when the bee lands on the stigma of another pea plant flower, cross- pollination occurs. What kind of symbiotic relationship is this? Mutualism – because the bee and the flower both benefit

7. Mendel wanted to know what would happen if he crossed two pea plants that had different traits. See Figure 4 on page 116. To be sure that the pea plant did not self-pollinate, he removed the anthers. He transferred pollen to the stigma of the pea plant without anthers.

8. Describe Mendel’s first set of experiments. Page 117 Mendel used pea plants that were true-breeding or homozygous for traits. For example, he crossed homozygous purple pea plants with homozygous white pea plants. All of the offspring had the dominant purple flowers.

9. Describe Mendel’s second set of experiments. Page 117. He allowed the first-generation plants to self- pollinate. By doing this, it was possible for the recessive traits to show up. For example, there might be pea plants with white flowers.

P P Pp PP Pp Pp Purple dominant - P White recessive - p pp First Generation of Offspring (F1) All Plants have purple flowers Pp Second Generation of Offspring (F2) PP Pp Pp pp On the average, for every three plants having purple flowers, there is one plant with white flowers.

10. Switch to Elmo to show Punnett squares.

How to remember genes and alleles… Genes – Inherited traits Examples: dimples, eye color, hair color, flower color, flower height If the gene is smile dimples… Alleles – Different forms of a gene. One allele is dimples The other allele is no dimples

Alleles are different forms of a gene. Gene – Eye color Alleles – Different Forms of a Gene Blue Brown Gray Green