Genetic Mutations What mistakes can occur when DNA is replicated?
Why?
The genes encoded in your DNA result in the production of proteins that perform
... [Show More] specific functions within your cells. Various environmental factors and spontaneous events can lead to changes in genes. These changes, called mutations, can lead to alterations in the structure and activity of the proteins your cells use in their daily activities. In other words, changes to your genotype can result in changes to your phenotype. We all have mutations in most of our body cells—yet we are, for the most part, normal and functional human beings. How can that be?
1. How many nucleotides are present in the “normal” DNA sequence in Model 1?
2. How many codons are contained in the mRNA that is produced by the “normal” DNA in Model 1?
3. How many amino acids will be in the polypeptide produced by the normal DNA/mRNA sequence and what is the sequence?
4. Consider DNA sequence 2 in Model 1. The mutation in that sequence is a substitution mutation.
a. Compare sequence 2 with sequence 1 and describe the mutation that has occurred.
ACC instead of AGC
b. What is the effect of this substitution mutation on the amino acid sequence?
It changes from Trp to Ser
5. Consider DNA sequence 3 in Model 1. The mutation in that sequence is an insertion mutation.
a. Compare sequence 3 with sequence 1 and describe the mutation that has occurred.
The first two are the same and all the rest are different
b. What is the effect of the insertion mutation on the amino acid sequence as compared to the “normal” amino acid sequence? It changed all of the amino acids after His
7. In your group, use grammatically correct sentences to define each of the following mutations.
12. For each of the mutations A – D in Model 2, circle the substitution that occurred by comparing the mutated DNA with the original DNA.
13. As a group, describe the range of changes in the amino acid sequence that can result from this type of mutation.
17. All cells have DNA errors due to the mistakes that occur each time DNA is replicated prior to cell division. There are proofreading enzymes in cells that correct many of these mistakes, but on average, 3 – 5 errors are found in DNA after each replication.
a. If each cell has multiple mutations, why do most of us have normally-functioning tissues and organs?
18. Insertion and deletion mutations are said to cause shifts in the “reading frame” (the sets of three nucleotides) of the mRNA. Substitution mutations do not cause these so-called frameshifts. Explain why insertions and deletions are called frameshift mutations, using the terms reading frame, codons, and amino acids in your answer. [Show Less]