DNA Replication
Paper Clip Simulation
Human Growth Hormone Gene Sequence (First Ten Bases)
A- A- G- C- T- T- A- T- G- G
T- T- C- G- A- A- T- A- C- C
COLOR KEY
BLUE- ADENINE
YELLOW- THYMINE
RED- CYTOSINE
GREEN- GUANINE
STEPS ONE TO THREE
STEP FOUR
STEP FIVE
STEP SIX
1. Examine the two double-stranded DNA molecules. Are they identical or different in any way?
The two DNA molecules are identical.
2. If you were asked to replicate each of the two DNA molecules on your table to create four identical DNA molecules, how would you go about doing this?
I would follow the same procedure used to replicate the first DNA molecule, as stated above. I would split the DNA molecule along the backbone and separate the bases, creating two single strands. Then I would pair the correct bases to each of the strands (A to T, C to G, etc.) in order to create two identical double strand molecules.
3. You now have two copies of a segment of the hGH gene on your table. During periods of growth and cell division, the chromosomes, which are made up of genes, must divide. What features about DNA replication causes each new DNA molecules to be exactly like the original?
DNA replication occurs with the involvement of many enzymes. The DNA molecule is unzipped and therefore separated into two single strands that we will call the "parent strands". These are then used as templates for the complementary base pairing that will take place. Since the A's will always go to the T's, the C's will always go to G's, and vice versa for each pair, the DNA molecule will then create identical "daughter strands" of itself through this process of using each of its halves as a template during replication.
So what is a gene mutation?
STEP SEVEN
4. When this mutated DNA molecule replicates, will the resulting new DNA be similar or different from the hGH gene? Explain.
When this DNA molecule replicates, the new DNA will be different from the hGH gene because the second base has been changed from an A to a C. Thus, when it is paired with a new base to create the daughter strand, it will be a C/G pair instead of the A/T pair, which should be the second base pair in the hGH sequence.
TOP: REPLICATED MUTATED GENE
BOTTOM: REPLICATED ORIGINAL GENE
5. Draw structures of the new double-stranded mutated gene you created by using the letters A, T, C, and G in a manner similar to that shown earlier.
A- C- G- C- T- T- A- T- G- G
T- G- C- G- A- A- T- A- C- C
Since the sequence of bases is different in this molecule, the genetic code is different. This gene CANNOT direct the cell to produce normal human growth hormone.
6. In your own words, explain how mutations can occur in cells and how this might affect the new organism with the mutation.
Mutations can occur from environmental factors such as UV radiation, or from mistakes during cell division. The organism with the mutation in the hGH may experience negative consequences from it. hGH is responsible for things like growth spurts through adolescence, muscle and bone growth, and the development of many bodily systems. Without the presence of normal human growth hormone, these functions may not be executed to the best of the body's ability and result in stunted growth and development of the adolescent.
