What happened when the purple flowered pea plants were allowed to self fertilize?
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Science >> Biology for Kids Mendel and InheritanceWhat is heredity?Heredity is when certain traits are passed from the parents to the children. Traits are characteristics such as eye color, height, and athletic ability. Heredity is passed through genes in the DNA molecule. In biology the study of heredity is called genetics. Show Gregor Mendel Scientist Gregor Mendel (1822 - 1884) is considered the father of the science of genetics. Through experimentation he found that certain traits were inherited following specific patterns. Gregor studied inheritance by experimenting with peas in his garden. Peas work as an excellent test subject as they can self-pollinate, cross fertilize, and have several traits that only have two forms. This enabled Mendel to easily control his experiments and reduced the possibility of the outcomes to something he could record and manage. Mendel's Experiments Gregor studied seven traits of the pea plant: seed color, seed shape, flower position, flower color, pod shape, pod color, and the stem length. There were three major steps to Mendel's experiments: 1. First he produced a parent generation of true-breeding plants. He made these by self-fertilizing the plants until he knew they bred true to the seven traits. For
example, the purple flowering plants always produced seeds that made purple flowers. He called these plants the P generation (for parent). Mendel's Results Mendel found some incredible results from his experiments. F1 Generation Mendel found that the F1 generation all produced the same trait. Even though the two parents had different traits, the offspring always had the same trait. For example, if he bred a P plant with a purple flower with a P plant with a white flower, all of the offspring (F1) plants would have purple flowers. This is because the purple flower is the dominate trait. These results can be shown in a diagram called a Punnett square. The dominate gene is shown with a capital letter and the recessive gene with a lower case letter. Here the purple is the dominant gene shown with a "P" and the white is the recessive gene shown with a "w." You can go to this page to learn more about inheritance patterns and Punnett Squares. F2 Generation In the F2 generation he found that 75% of the flowers were purple and 25% were white. Even though both parents had purple flowers, 25% of the offspring had white flowers. This turned out to be because of a recessive gene or trait was present in both parents. Here is the Punnett square showing that 25% of the offspring had two "w" genes causing them to have white flowers: Homozygous and Heterozygous When two of the genes are the same (like with "PP" or "ww" above) they are called homozygous. When they are different (like with "Pw") they are called Heterozygous. Interesting Facts about Mendel and Inheritance
Science >> Biology for Kids BackgroundIn this web lab, students experiment with garden pea plants (Pisum sativum) as did Austrian monk Gregor Mendel (1822-1884). Mendel chose to experiment with peas because they possessed four important qualities:
The traits that Mendel studied are listed below:
The Web Lab This web lab has five sections that are accessible through the “Sections” button in the lower left-hand corner of the screen. Students can explore the
entire web lab by clicking through or can jump to specific sections by using the menu. Each section is described below. IntroductionMendel is the guide for students throughout the web lab. When he first appears, he says, “Hello. My name is Gregor Mendel. I lived in Austria in the 1800s long before anyone knew about genes and genetics. I experimented with plants to study how traits are passed from parents to offspring ad discovered the basic rules of inheritance that are
still used in your textbooks today. Come and try some of my experiments to see what you can discover about inheritance. Click Next to continue.” The next text reads, “I used pea plants because they grow quickly and easily, and it is easy to see and recognize their different traits.” Plant & CrossThis section of the web lab allows students to explore the traits on which Mendel experimented, then cross pea plants to see what offspring they produce. Mendel
urges students to, “Plant five pea plants and observe what they look like.” When students click the “Plant” button, the animated Mendel plants and waters five pea plants. Each of the pea plants quickly sprouts. By rolling over the plants with the cursor, the student can see the color of the pea pod, the shape of the pod, and the color and form of the ripe seed. All of the different variations of pea plant can be seen in these growing peas, although the plants are randomly chosen each
time the application is run. After they have planted and grown five plants, Mendel asks students how many distinguishing traits they see in the plants. On the next screen, he reveals that there are seven different traits:
These traits are all pictured in the plants below: Students are then asked to experiment with plant crosses. Using the five plants that they grew, they can cross any plant with itself or with another plant. Students may begin to notice some patterns in the ways in which traits are inherited. For example, they may recognize that a plant with
white flowers crossed with itself or another plant with white flowers will produce only white flowered plants, while a purple-flowered plant crossed with itself or another purple-flowered plant sometimes produces white-flowered offspring. By encouraging students to look at individual traits during their experimentation, you may find that they begin to recognize these patterns on their own. After they have made five crosses, the Next button is enabled and students can move on to the
following section. Predict ResultsIn this section of the web lab, students explore plant crosses and predict what the offspring of these crosses will look like. A plant with round peas and a random assortment of other traits appears on the screen. Mendel says “Cross this plant with itself. What pea shapes do the offspring have?” When the student drags the plant into one of the Parent boxes, the Cross button appears. When the student clicks the Cross
button, five offspring grow. Some of the offspring from the plant with round peas have wrinkled peas. Mendel then asks, “Were you surprised that a plant with round peas produced some offspring with wrinkled peas?” A plant with wrinkled peas appears on the screen and students are asked to cross this plant with itself. As before, when the student drags the plant into one of the Parent boxes, the Cross button appears. When the student clicks the Cross button, five offspring grow. Mendel appears and says, “What did you learn about your peas?” Students will probably recognize that, while a plant with round peas produced some offspring with wrinkled peas, the plant with wrinkled peas produced only offspring with wrinkled peas. This is one key to Mendel’s experimentation—a trait that was not apparent in a parent generation appeared in the F1 generation. When the student click Next, two plants appear on the screen, both with wrinkled peas. The student is asked to
predict the offsprings’ pea shapes (both round and wrinkled; all round; all wrinkled; or can’t predict). Because the allele that produces wrinkled peas is recessive, the offspring of this cross will all have wrinkled peas. Mendel then explains the concept of dominant and recessive alleles by saying, “By performing my experiments with peas, I learned a lot about genetics and how traits are passed on. I noticed that sometimes offspring seem to have traits that their parents did not
show. I called the traits that appeared to mask (or hide) other traits dominant. I called traits that seemed to be hidden recessive.” PedigreeIn this section of the web lab, students experiment with pea plants to try to discover which alleles are dominant and which are recessive. Using four different pea plants, students can cross plants with themselves or with each other to determine dominance. One strategy that students might employ is to cross plants with
themselves—offspring that show a different trait than the parent of such a cross possess the recessive allele (which was hidden by the dominant allele in the parent generation). Mendel says, “Using these plants, figure out how the trait for flower color is passed on. Which color is dominant, white or purple? This is a pedigree. You can cross plants with themselves or with each other.” When a student clicks on one of the plant symbols (a white or a black box), the cross button
appears. If the student selects two plants, then the two plants are crossed and the offspring appear below. If a student selects only one plant and clicks the Cross button, then the plant self-fertilizes and the offspring appear below. Students can cross plants as many times as they want before deciding which allele is dominant. ExploreStudents can explore all seven of the pea traits that Mendel explored in this section. Four pea plants appear in the pedigree and students
can select which trait they are looking at with the pulldown menu in the upper left corner of the screen. When students have determined which alleles are dominant, they can record their choices in their notepads by clicking on the View Notepad button. The Check button allows students to check the answers they have input into their notepads. The following table shows each of the traits and which traits are dominant and which recessive.
GlossaryAxial Flowers located near the middle of the plant. Dominant Traits that appear to mask (or hide) other traits. Pedigree A diagram of a family history used for tracing a trait through several generations. Recessive Traits that can be hidden in one generation and then appear in the next. Terminal Flowers located at the ends of the stems. Trait A distinguishing characteristic. What happened to the experiment of pea plant?Mendel crossed pure lines of pea plants. Dominant traits, like purple flower colour, appeared in the first-generation hybrids (F1), whereas recessive traits, like white flower colour, were masked. However, recessive traits reappeared in second-generation (F2) pea plants in a ratio of 3:1 (dominant to recessive).
What happened when Mendel allowed the F1 plants to self pollinate?To test this prediction, Mendel allowed the F1 generation plants to self-pollinate. He was surprised by the results. Some of the F2 generation plants had white flowers. He studied hundreds of F2 generation plants, and for every three purple-flowered plants, there was an average of one white-flowered plant.
Are pea plants self fertilizing?Pea flowers are perfect and self- pollinating. The flowers open early in the morning and do not shut. The anthers shed pollen the night before the flower opens, but this does not reach the stigma until the flower is tripped, usually by the wind.
How did Gregor Mendel keep his pea plants from selfTo perform his experiments, how did Mendel prevent pea flowers from self-pollinating and control their cross-pollination? He cut away the pollen-bearing male parts of a flower and dusted that flower with pollen from another plant.
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