Question

Mutation 1. A chromosomes has the following segments, where represents the centromere: MNOPQRST Give the chromosome sequences that would result from the following mutations: a. Deletion of MN Pericentric inversion of NOP C. Inversion of RS, followed by tandem duplication of QRST b. 2. Which type(s) of chromosomal mutations: a. Increase the amount of genetic material in a particular chromosome? b. Increase the amount of genetic material in the entire genome? c. Decrease the amount of genetic material in a particular chromosome? d. Change the position of DNA sequences in a single chromosome without changing the amount of genetic material? e. Move DNA from one chromosome to a nonhomologous chromosome 3. Most mutations are thought to be deleterious. Why, then, is it reasonable to state that mutations are essential to the evolutionary process? 4. A codon that specifies the amino acid glycine (Gly) undergoes a single-base substitution to become a stop codon. a. At which position of the codon does the mutation occur? b. Is this mutation a transition or a transversion? e Is it a missense or a nonsense mutation? 5. Assume that an Ames test is performed on a new compound. Tube I contains distilled water as a control, tube 2 contains the compound, and tube 3 contains the compound
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Answer 1

4.a) The codons for glycine are GGT, GGC, GGA, GGG. The three STOP codons are UAG, UGA, and UAA. Any single base substitution mutation that could turn the glycine codon to stop codon must takes place in the GGA. The G is replaced by U so that it becomes UGA, which is a stop codon.

b)Guanine is a purine and Uracil is a pyrimidine. Thus the mutation is a transversion mutation since the purine is replaced for pyrimidine. In a transition mutation, the change happens within the purine or within pyrimidine.

c)This is a nonsense mutation since the sense codon that corresponds to one of the twenty amino acids specified by the genetic code is changed to a chain-terminating codon. A missense mutation occurs when one DNA nucleotide is changed so that different amino acid is inserted into a protein. Here the mutation results in the stop codon.