Discovering the Molecular Structure of Genetic Material Introduction: So far, we have seen how chromosomes behave in both body and reproductive cells (inside the gonads) and we have also examined how traits are passed on to offspring. We have seen that the number of chromosomes is cut in half in the creation of gametes (haploid cells, sperm and eggs) during meiosis. We also have explored the idea that when haploid cells combine to form a diploid zygote, alleles for different traits combine. These alleles are then expressed in different ways, some of which you have heard of (complete dominance, incomplete dominance, codominance) to create many different phenotypes. However, we are struck with the question: WHAT exactly are genes anyway?!?! In this project, you will be given the opportunity to become even more familiar with a number of important discoveries about the chemical nature and composition of chromosomes, and you will attempt to create and test a model of the molecule that carries genetic information. The model should (eventually) tell you how information is passed from parent to offspring. Remember James Watson and Francis Crik? You will be undertaking the same process that resulted in their winning of the Nobel Prize in 1962. By the end, you will read three sets of “historical clues” – these are basically timelines of important discoveries about chromosomes from 1860 all the way to 1953. You will read each set one at a time, and develop a model after reading each set. DO NOT TRY AND READ THE CLUES ALL AT ONCE! It is far too overwhelming! Don’t be discouraged if you had difficulty understanding these readings, they are not leisure reading. Don’t get frustrated if you do not understand it right away. Read through each set a few times before you continue. It is perfectly normal to ask questions about things you don’t understand, so a large part of this project is to ASK/pose questions which you need to answer in order to proceed. Try
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Transcript
Discovering the Molecular Structure of Genetic Material
Introduction:
So far, we have seen how chromosomes behave in both body and reproductive cells (inside the gonads) and we have also examined how traits are passed on to offspring. We have seen that the number of chromosomes is cut in half in the creation of gametes (haploid cells, sperm and eggs) during meiosis. We also have explored the idea that when haploid cells combine to form a diploid zygote, alleles for different traits combine. These alleles are then expressed in different ways, some of which you have heard of (complete dominance, incomplete dominance, codominance) to create many different phenotypes. However, we are struck with the question: WHAT exactly are genes anyway?!?!
In this project, you will be given the opportunity to become even more familiar with a number of important discoveries about the chemical nature and composition of chromosomes, and you will attempt to create and test a model of the molecule that carries genetic information. The model should (eventually) tell you how information is passed from parent to offspring. Remember James Watson and Francis Crik? You will be undertaking the same process that resulted in their winning of the Nobel Prize in 1962.
By the end, you will read three sets of “historical clues” – these are basically timelines of important discoveries about chromosomes from 1860 all the way to 1953. You will read each set one at a time, and develop a model after reading each set. DO NOT TRY AND READ THE CLUES ALL AT ONCE! It is far too overwhelming!
Don’t be discouraged if you had difficulty understanding these readings, they are not leisure reading. Don’t get frustrated if you do not understand it right away. Read through each set a few times before you continue. It is perfectly normal to ask questions about things you don’t understand, so a large part of this project is to ASK/pose questions which you need to answer in order to proceed. Try to write your questions as clearly as possible. They might invoke a large class discussion, others may be answered on your own.
After we have completed the models, we will run through the model together.
Procedure:
1. You are trying to answer two essential questions:a.) What molecules make up the genetic material in
chromosomes?b.) What is the nature of these molecules? (How do they behave? How are they arranged?)
2. Read the six clues from clue set 1. Write five questions on the sheet labeled “THIS IS A QUESTION SHEET” that you have about the set of clues; we will be discussing these in the next class. 3. It is supposed that chromosomes carry genetic information, the question arises:
What molecule in the chromosomes carries the genetic information?
Write out two alternate hypotheses that you- as a scientist might pose after reading the clues (especially after clue #1) TO ANSWER the above question
4. Which of these hypotheses seems most likely to be able to be supported, based on the work done from 1900 – 1952?Give a few examples to support your idea!