Mutations can cause a huge variety of effects, including proteins that don't work (loss-of-function) and proteins that are too active (gain-of-function). Not all mutations are loss-of-function. Mutations can be inherited or from environmental factors, and many times a mutation will mean nothing at all for the organism.

A nonsense mutation will cause the protein to never be completed because of a premature stop codon, hence the protein "never makes sense," ie nonsense. Missense will make a protein with the incorrect amino acid sequence. A point mutation can cause a nonsense mutation, but is not the best answer, as it is vague. The other two mutations also theoretically can cause a nonsense mutation, but nonsense is most specific answer.

The most deleterious mutation would be a frameshift mutation. This would attained by inserting or deleting multiples of 1 or 2 bases in any important coding regions (exons, splice site, translation start site). Inserting or deleting multiples of 3 bases would not cause a frameshift mutation. A mutation in 3' UTR or intron would essentially have minimal effects. A mutation in the wobble position would most likely not change the amino acid.

Recall that a frameshift mutation occurs when part of one or more codons in lost in such a way that the entire sequence of codons "shifts," making the transcribed mRNA translate as a different pattern of amino acids during protein synthesis. This is a big problem, since it means that a sequence of DNA coding for a specific protein now likely codes for a completely, fundamentally different one.

The correct answer is:

A T G C T G G A T A G C T A

T A C G A C C T A T C G A T

Compare to the original DNA, and note where one base pair was removed:

A T G C C T G G A T A G C T A

T A C G G A C C T A T C G A T

The codons on a piece of mRNA transcribed from the top strand of the non-mutated form would read:

UAC GGA CCU AUC GAU

However, mRNA transcribed from the mutated DNA would read:

UAC GAC CUA UCG AT\[ \] (we don't know the last codon, since the next base pair is not given)

This is a serious issue. The non-mutated form codes for these first four amino acids...

tyr gly pro ile

...while the mutated form codes for these first four amino acids:

tyr asp leu ser

Clearly, frameshift mutations can be very dangerous.

Sub-metacentric is when the the centromere is off to one side. Metacentric is when the centromere is in the middle. Acrocentric is when the centromere is at one end. Lop-centric is not a real thing.

It is an insertion because a nucleic acid was added to the sequence.

Point mutations occur when one nucleic base is swapped for a different nucleic base.