Instructional Notes: DNA Puzzle Pieces Lab Part II

Instructional Notes: DNA Puzzle Pieces Lab – Part II

Apparatus:

Pre-cut DNA pieces from Part I Additional Pre-cut DNA pieces to complete Part II Student generated table Tape

Pre-Lab Discussion:

This part of the lab will take what they learned about the structure and introduce the idea of DNA replication. Teacher will pose the question, “What happens when we need to make a copy of DNA?” as a discussion to lead them into the activity. Teacher will lead them to the idea that the nucleotides used to construct the new strand of DNA are free-floating in the cell. Teacher will ask the students what the repeating pieces in a DNA strand were called, and then plant the idea that you cannot just look through them to see what the bases are and make a duplicate strand. (This will help to prevent them from just copying their original strand and actually pull apart the strands and build complimentary strands.)

Instructions:

 Students are going to need to reproduce their original strand of DNA from their table using the pieces in bag 1 (bag used in Part-I).  Students will then need to figure out how to get two strands of DNA from their original strand. Teacher gives each group bag 2 that contains 20 phosphate, 20 sugar, and 5 of each base. (NOTE: Teacher should remind them that pieces need to get back in the correct bags at the end) o Teacher needs to remind them that they cannot just copy the strand on the side, that DNA builds the new strands one piece at a time.)  Students will need to add a new table and record what their new strands are made up of.

Example of new table is provided below: Order of Bases First Molecule Second Strand Left Right Left Right

Post-Lab Discussion:

Students will re-whiteboard their results and show their two new strands. They will then have a board meeting about what they see between each other’s models. The students will be prompted by the teacher on what do they notice between their two strands before they do their whiteboard meeting. As the students conduct the meeting they will see if everyone got the same result between their comparisons. As they are working through their discussion the teacher will prompt them with some questions to further the discussion.

 What were the strands of DNA being held together by? How did you get them apart? (Used to introduce the DNA Helicase, they should come to the conclusion that bonds were broken and the teacher can supply the name of what breaks them.)  If they have not come to the idea of daughter strands the teacher can prompt them with, “Did the original strands stay together?  Did the nucleotides put themselves together? (They were the DNA Polymerase bringing in the nucleotide and stitching things together. Use this to introduce DNA Polymerase).  What was the overall product?  What if there is a mistake? (Can be used to introduce the idea of proofreading by DNA Polymerase)

Prior to releasing the students to work on their analysis questions the teacher will use a model of their own (or a student’s model) and reenact DNA replication using all of the new terminology with the pieces that are found on the second page of the document with the puzzle pieces. Overall conclusions will lead the students to the idea that there are pieces involved in breaking the hydrogen bonds as well as putting everything back together. They can use the terminology they are provided by the teacher to help them answer the analysis questions they have at the end of their lab. They will then write a summary over Part-II tying in anything that is relevant from Part-I.

They will be exposed to the following essential vocabulary in this lab:

 DNA Polymerase  DNA Helicase  DNA Replication  Daughter Strand  Parent Strand  Replication Fork