How are traits passed from one generation to the next?

Transcription

1 How are traits passed from one generation to the next? Since the dawn of agriculture, humans have been trying to improve and increase their food supply. Historically, this was done by selecting the best plants and animals, then breeding them to get the tastiest, hardiest, most nutritious, or most appealing offspring. However, no one really understood how these traits were inherited. Many people believed that traits blended in the offspring, or that only one parent passed a trait on to its offspring. In the mid-800 s, a monk by the name of Gregor Mendel gathered the first evidence that began to explain how traits were passed. Mendel s repetitious work with pea plants yielded our elementary understanding of genetics and inheritance. In this investigation, you will gather your own evidence in order to better explain HOW inheritance works. As you observe TWO generations of Wisconsin Fast Plants, you will unravel a mystery of inheritance: How is hairiness inherited? What is the significance of plant hair? Is hairiness purely genetic? You will use your powers of observation and various generations of plants to serve as evidence to support or refute your answers to these questions. the Investigation Within the population of Fast Plants there is a phenotypic trait that might escape some students notice, but which lends itself easily to the investigation of variation and inheritance. Plant hairs can be seen along the stem, on the upper and lower surfaces of the leaves, on leaf edges and even on the buds of Fast Plants. Scientists have several theories as to the use of plant hair, but a concrete answer has yet to be found. The genetics of plant hair inheritance has yet to be explained satisfactorily. The number of different genes or alleles that control the number and location of plant hair is also unknown. Observing and counting the hairs is the first step in understanding how hair is inherited and influenced. The expression of the hairy phenotype appears to be under the control of a number of genes and is considered to be a polygenic trait. For this reason, our experiment will be using Fast Plants from two specific stocks: Hairless, Hir (0-), and hairy, Hir (-6). The hairy phenotype is described as Hir (-6). The symbol Hir is Latin for hirsute=hair. As with phenotypes which show a wide variation intheir expression, a scale from (0-9) can be used. On the scale, Hir values are as follows: Hir 0 Hir - Hir -6 Hir 7-8 Hir 9 No hair expression Low expression (few hairs) Intermediate expression (some hairs) High expression (many hairs) Very High Expression (very hairy)

2 Your Challenge The goal of this investigation is to determine Who s Hairy? You and your group will gather evidence to explain how hairiness in Wisconsin Fast Plants is inherited. From your evidence and explanations, you will predict the mode of inheritance and what (if anything) influences gene expression for this trait. Daily Activities Day : Working in your small group, follow the Wisconsin Fast Plants Growing Instructions and plant your four quads. LABEL the quads as follows: o Quad # o Quad # o Quad # o Quad # Days -: You need to water your plants daily. Day -5-Water and Thin (if necessary) Approximately Day 9: The first true leaf will develop. This leaf is an easy place to make your hair counts. You will need good lighting, a hand lens, and dark construction paper (at times it is easier to see plant hairs due to the contrast of light hair to dark paper). *Hairs can be counted form the base of the leaf, where it connects to the stem, to the center of the leaf tip. You should always count hairs on the same side. Record your hair counts in the table below and assign an Hir value. Day : Repeat your steps from Day 9. Record your findings below. Pre-lab Question(s). Explain how you believe hairiness is inherited. Provide a potential reason for your belief.

3 . Based on the current information do you think that genes for height are linked to genes for hair? Provide a reason for your prediction. Day : Following your Growing Instructions you are going to cross pollinate your plants. HOWEVER, we are interested in hairy inheritance. Can you make a SUPER hairy offspring? Would two SUPER hairy plants create hairless offspring? What does it depend on? Using the bee, pollinate your two HAIRIEST PLANTS with one another. When you have completed this task, remove your other plants. (the ones you did not pollinate). Day -6: You will need to pollinate your plants each day. Pre-lab Question:. Based on your findings so far, predict the Hir value of the first generation of offspring (F ) that will result from your pollinations. Explain why you believe this to be so. Day 7-5: Observe your plants daily. If new flowers open, you may remove their blossoms. Remember to water every day you are in class. Make your own observations. What data should you collect? (Place your data on a clean sheet of paper and keep it in your folder) Day 0: (F ) Seeds are harvested as discussed in Growing Instructions. Day 0: (F ) Seeds are planted as discussed in Growing Instructions. Day 0-: Plants will be watered daily. Day 5: Thin and transplant plants if needed. Approximately Day 9: The first true leaf will develop. This leaf is an easy place to make your hair counts. You will need good lighting, a hand lens, and dark construction paper (at times it is easier to see plant hairs due to the contrast of light hair to dark paper). *Hairs can be counted form the base of the leaf, where it connects to the stem, to the center of the leaf tip. You should always count hairs on the same side. Record your hair counts in the table below and assign an Hir value.

4 Day 5: Repeat your steps from Day 9. Record your findings below. Lab Question(s):. Looking at yours/class data from the (F ) generation, what can you conclude about hair gene expression?. Looking at your data from both the (P /P ) and (F ) generations, what can you conclude about the genotype of EACH generation?. Does the class data refute or confirm your original thoughts concerning the potential connection between plant height and hairiness? Explain your answer.

5 Hairiness in Plants Paper (90 points) Paper is typed and double spaced Paper maintains the correct font (pt) and margins settings ( ) Paper contains an introduction, supporting paragraphs and a conclusion What were you trying to accomplish? How is hairiness inherited? *Data used to support your conclusions *Genotype/Phenotype discussed concerning P, P and F Hairiness is considered a polygenic and multifactorial trait. Identify these terms and explain how they relate to hairiness in plants. Use examples to strengthen your argument. Will offspring have more hair than their parents? Why or why not? Will hair in the offspring be found in the same location as in the parental generation? Why or why not? Do other plant traits play a part in hairiness? Explain, using examples. Why do plants have hair? Under what conditions would hair be an advantage? How can the environment influence hairiness? points 9 points points 0 points points 0 points