Gregor Mendel  Austrian scientist who discovered basic ideas of heredity while working with the pea plant

Self-Pollinating Peas  Pea plants grow quickly  Peas self-pollinate = has both male and female reproductive structures  Pollen from ONE flower can fertilize the ovule of the SAME flower and/or the ovule from another plant

Flower Power  PEDUNCLE—stalk of the flower  RECEPTACLE—part of the stalk where the flower is attached  SEPAL—the outer parts of the flower that wrap up the growing bud  PETAL—the colored parts of the flower  STAMEN—pollen producing part of the flower  ANTHER—part of stamen where pollen is produced  PISTIL—ovule producing part of a flower; ovary often supports a long style, topped by a stigma; mature ovary is a fruit and the mature ovule is a seed  STIGMA—part of the pistil where pollen germinates  OVARY—enlarged basal portion of the pistil where ovules are produced

Self-Pollinating Plants  Why is it important that pea plants self-pollinate?  Eggs and sperm from the same plant combine to form a new plant which was actually a TRUE- BREEDING PLANT  True-Breeding Plants self- pollinate and create offspring that will have the same trait (ex—the color of the petals) as the parent

Self-Pollinating Plants  Pea plants also CROSS- POLLINATE  Cross-pollination = pollen from one plant fertilizes the ovule of a flower on a different plant  Pollen can be carried by insects (ex—a bee), the wind, birds, and other small creatures

Characteristics  Characteristic = a feature that has different forms in a population (ex—hair color in humans)  Mendel used plants that has different characteristics in order to figure out how he could change those characteristics in offspring (ex—flowers that were one color may produce offspring with a different color)

Mendel’s First Experiments  1 st Experiment—studies 7 different characteristics  He used plants that were true-breeding for different traits for each characteristic (ex—crossed plants with purple flowers with plants that had white flowers)  FIRST-GENERATION PLANTS = the offspring from a cross [see above]

Mendel’s First Experiments  Similar results were discovered with each cross  DOMINANT TRAIT = the trait that is always present in the first generation  RECESSIVE TRAIT = the trait that always seemed to disappear in the first generation

Mendel’s Second Experiments  Mendel allowed the first- generation plants to self- pollinate  The recessive trait for white flowers reappeared in the 2 nd generation!  After repeating the experiment on each of the 7 characteristics Mendel learned that in the 2 nd generation the recessive trait reappeared in some of the plants

Ratios in Mendel’s Experiments  The recessive trait did not show up as often as the dominant trait  Ratio = a relationship between two different numbers that is often expressed as a fraction  Dominant-to-Recessive Ratio

Section Review  Please complete the entire Section Review on page 61 of your textbook!