Really, this blog should be read from the bottom up. Since the pictures insist on adding to the top of the page, this information is basically backwards and progresses from the bottom up.
Overall, I really enjoyed this lab! I am much better with this hands-on, visual learning. I found it very interesting, and my family even jumped in to help. (See above pictures.) :)
Finally, I have tried to show the process of DNA transcription to mRNA, and mRNA translation to proteins. I have to admit, this part was challenging for me. I truly had to read and re-read, and then talk it over with my husband before I felt confident enough to build it with full understanding. I must say, I found it very confusing until I built the model myself. Now, I feel like I actually have a true understanding of this process. First, DNA transcription occurs within the nucleus. During this process, DNA (the blueprint for synthesizing proteins is unzipped and a strand of mRNA froms that is complimentary to a portion of DNA. This is a transcript (exact copy) of the gene. This all happens before the mRNA is processed and it leaves the nucleus. Next, the mRNA strand breaks free from the DNA and moves through the membrane of the nucleus out into the cytoplasm. It then attaches to ribosomes. Amino acids are carried to the ribosomes be tRNA, and the ribosomes then translate mRNA to a specific amino acid sequence. The amino acid sequence then folds up into a protein. Proteins are vital because they catalyze reactions of cell metabolism. This is gene expression. For this, I used the twizzlers to again represent the DNA, with a different color coming off of one strand to show the mRNA. I used a few spaghettie strands to represent the nuclear membrane that mRNA passes through. I chose to use a baked potato to represent the ribosomes, and "Stackers" candy to signify the amino acids and peptide. Finally, I used the small twizzler candy to represent tRNA.
Next is mitosis. The goal of mitosis is to produce two identical daughter cells. We need these new cells from growth and replacement and repair of damaged cells. The first phase of mitosis is Prophase. During this stage, chromosomes condense and become visible, the nuclear envelope fragments and the nucleolus disappears. The Centrosomes move to opposite poles, and spindle fibers appear and attach to the centromere. The next stage is Metaphase,during which chromosomes line up at the middle of the cell (equator), and a fully formed spindle is present. Next is Anaphase, when sister chromatids separate at the centromeres and move towards the poles. Finally, in Telephase and Cytokinesis, the nuclear envelope begins to reassemble around the two daughter neclei. This all results in the division of the cytoplasm and the creation of two new cells, or Interphase. For this model, I used a cantalope halves to represent the cells, twister candy to represent the chromosomes, and a different version of twizzlers to represent the centrioles.
Next, I built a model in order to show the process of DNA replication. DNA replicates to pass on information to daughter cells during the process of mytosis. First, you will again see the cell and the nucleus. During DNA replication, the helix of the DNA is duplicated. The double-stranded structure of DNA allows each original strand to serve as a template for the formation of a complementary new strand. It is considered semiconservative, because each new double helix has one original strand and one new strand. Each original strand produces a new strand through complimentary base pairing. All of this results in two DNA helices identical to eachother and to the original molecule. In DNA replication, the double helix is unzipped, and two new strands of DNA are formed. So, what you are seeing in my pictures is first, the nucleus in the cell, then the nucleus by itself containing chromosomes, then a close-up shot of a chromosome, and then an even closer view of what the chromosome actually is: a double DNA helix. Finally, you will see the helix "unzipped", creating two new identical strands. The materials I used for this portion of the lab were: my original cell model, a grapefruit half with candy placed on it to represent chromosomes, colored twizzlers to represent DNA strands, and colored toothpicks to show the bases.
I decided to build my cell out of edible objects. Here are the components of the cell with their definitions / functions. I will also provide the materials I used for each part next to the definition. (Note: the cell as a whole is represented by bread dough.)
- Cell Membrane: The outer surface of a cell that regulates the entrance and exit of molecules into the cell. ("Hard" outer crust of dough.)
Nucleus with nuclear membrane: Membrane-bound organelle that contains chromosomes and controls the structure and function of the cell. The nuclear membrane encloses the nucleus. (Grapefruit = nucleus, grapefruit rind = nuclear membrane.
- Endoplasmic reticulum: System of membranous saccules and channels in the cytoplasm, often with attached ribosomes. Rough ER: studded with ribosomes. Smooth ER: Lacks ribosomes, synthesizes lipid molecules. (Rough ER: Blue spaghetti with corn kernels. Smooth ER: Brown penne noodles cut to different shapes and sizes.)
- Golgi Apparatus: Processes, packages and secretes modified cell products. (Green beans, opened and de-seeded.)
- Lysosomes: Vesicle that digests macromolecules and even cell parts. (Purple jelly beans.)
- Vesicles: Membrane-bounded sac that stores and transports substances. (Peas)
- Mitochondria: Organelle that carries out cellular respiration, producing ATP molecules. (Baby red potatos)
- Cilia: Made of microtubules. Short, hairlike projection from the plasma membrane. (Red food coloring, mixed in with dough.)
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