Biology 9 Lesson 20: Practice: Observe and assemble a DNA model
1. Theoretical Summary
a. Knowledge of DNA models
– According to the model of Wat-son and Crick:
The DNA molecule is a double helix consisting of two polynucleotide chains twisted around an imaginary axis. Twist to the right. To form a torsion cycle, there are 1 large groove and 1 small groove.
+ The ladders are nitrogenous bases and the walls and handrails are sugar molecules and phosphate groups.
DNA is a double helix consisting of two parallel strands. The nucleotides between the two bonds form pairs according to the principle of A – T complement; GX (opposite)
+ Helix diameter 2 nm (20 Ao), 1 high period 3.4 nm (34 Ao) including 10 nucleotide pairs.
b. Preparing instruments
- The model of the DNA molecule has been finely assembled.
- The box contains a model of the molecular structure of DNA in disassembled form with the number corresponding to the number of groups of students.
- Monitor and projector or light source (electrical bulb).
- CD, VIDEO (with content on structure, mechanism of replication, mechanism of RNA synthesis, mechanism of protein synthesis).
2. Practice Procedure
– Install a complete circuit first, go from the base up: Choose the curvature of the segment to be reasonable
– The installation of the second circuit must comply with NTBS and have a corresponding and regular curvature with circuit 1.
– When the model is finished installing, it is necessary to check the following:
- Twist direction of 2 circuits
- Equal distance between the two circuits.
- The number of nucleotide pairs per helix period.
- NTBS pair binding between nucleotides.
3. Report on the group’s practice results
The groups take turns to evaluate the performance report
First and last name ………….
After completing this lesson, you should:
- Complete the DNA model correctly.
- Understand the structure of DNA.