A point mutation that substitutes a single nucleotide within a gene alters the three nucleotides that make up an individual codon. There are four possible nucleotides and sixty-four possible codons, formed by 3-nucleotide sequences. Codons code for translation to one of the twenty amino acids. Changing a single nucleotide in the codon can have one of three effects.

First, it can result in a silent mutation. This is a result of the degeneracy of the genetic code, in which multiple codons can code for the same amino acid. Even though the sequence is different, the same amino acid is added. For example, if the sequence is initially CCT it will code for proline. If a mutation changes it to CCC it will still code for proline.

The second option is a missense mutation. In this case, the change in DNA sequence results in a codon for a different amino acid. For example, a mutation from TTT to TCT will change the amino acid from phenylalanine to serine.

Finally, the mutation could change a codon to a stop codon, causing early termination of translation. This is a nonsense mutation. For example, changing the TAT codon for tyrosine to TAA will result in an mRNA stop codon.

No matter how the point mutation affects the final protein product and codon sequence, it will still be transcribed into mRNA.

A nonsense mutation results in a stop codon. This can be the result of an insertion or a deletion, causing a change in the DNA sequence from a normal amino acid codon to one of the three possible stop codon sequences.

A missense mutation changes the identity of a codon from one amino acid to another, resulting in a change to the protein primary structure. A silent mutation occurs when a mutation does not change the amino acid coded for by that codon. A frameshift mutation is an insertion or deletion that changes the reading frame of the entire protein and can have severe detrimental effects. A radioactive mutation is not a specific classification of mutations. 

This mutation is dominant because whatever mutation occurred at the genomic level was sufficient to cause an amino acid switch, i.e., it was expressed. If this were recessive, we would see that the nucleotide base change would not have yielded a knock out. Recall that only one copy of a "bad" gene is required for it to be expressed if it is a dominant mutation, whereas two copies of the "bad" gene are required for it to be expressed if it is a recessive mutation. No information is provided to consider sex linked traits.

The problem states that there was no change in gene size between the two specimens. That means that the mutant and the control still had the same number of nucleotide bases. Out of all options provided, substitution is the only possible type of mutation that fulfills the description. Deletion, insertion, nonsense and frameshift mutations would have all lead to a size discrepancy. 

The change introduces an extra "T' near the beginning of the sequence. This mutation will change the frame of the codons of the gene, and result in a frameshift mutation.

Translocation is when two different chromosomes exchange large parts of the genetic sequence. 

A nonsense mutation arises when a point mutation in DNA causes a mRNA strand to have a stop codon prematurely. It changes a base that would have led to an amino acid to a base that makes that triplet codon to a stop codon. This causes the ribosome to stop making the protein too soon and results in a shorter protein. The name arises from the drastic effect this has on the function of the protein. 

While biologically important, the other choices are incorrect. An insertion mutation changes the number of bases in that segment of DNA—extra is base added. On the other hand, a missense mutation switches one amino acid for another in that sequence. Last, a frameshift mutation changes the reading frame of three codons. So if a gene in DNA has the following sequence (keeping in mind that there are two strands not one):

ACTATTCCCGGATTC 

The resulting RNA sequence would be as follows:

UGAUAAGGGCCUAAG

A frameshift mutation would occur if a mutation caused thymine to be inserted into the first codon in the following DNA sequence:

ATCTATTCCCGGATTC

As a result, the resulting mRNA sequence would be the following:

UAGAUAAGGGCCUAAG

The entire reading frame has been changed. Because they have been moved over by one base all the triplet have been changed; therefore, each triplet is off by one base.

Given the explanation provided, a transition is a mutation that mutates a purine to another purine, or a pyrimidine to another pyrimidine. The best way to solve is to assign the nucleotide as a purine or pyrimidine. To answer this, you must know that purines include adenine and guanine and pyrimidines include thymine, cytosine, and (in RNA) uracil. 

Mutations and evolution must be distinctly defined. Mutations happen to individuals. To acquire a mutation, a single event will cause the DNA of a single individual to become altered. If the result is a positive mutation, meaning the change helps increase the fitness of the individual (ability to reproduce), then it will get passed on to the next generation.

Evolution affects a population when mutations change the genetic variety of individuals. As a mutation spreads through the population by reproduction and inheritance it changes the genome of the species. As more and more mutations are acquired in the population, speciation can eventually occur.

Mutations are not goal-directed. A mutation simply happens, and does not arise as a result of environmental necessities.

Alleles are different nucleotide sequences at a given gene's location. Different alleles generate different forms of the same protein product. Repair flaws caused by radiation and chemical damage change the nucleotide sequence, causing mutations. Mutations alter the gene pool, and are therefore the source of new alleles. These mutations are the foundation of evolutionary change and diversity among life-forms.