Question

Which of the following mutations is most likely to result in a non-functional protein?

a) a single-nucleotide substitution in a promoter

b) an insertion in an intron

c) a frameshift mutation

d) a missense mutation

You have conducted an Ames test on a given compound to determine whether it is a mutagen. Which of the following would be classified as a positive result on the Ames test?

a) originally His+ strain grows on minimal medium with histidine.

b) originally His+ strain grows on minimal medium either with or without histidine.

c) originally His+ strain grows on minimal medium.

d) originally His- strain grows on minimal medium with histidine.

e) originally His- strain grows on minimal medium.

To integrate an F plasmid's genes into a host chromosome, there must be DNA recombination at homologous regions on the two circular strands. What is the minimum number of such crossover events needed for integration?

a) 5

b) 1

c) 2

d) 0

e) 3 4.

Which of the following events creates partial diploids?

a) The genes of the F plasmid and some chromosomal genes are excised from the chromosome of an Hfr strain

b) Conjugation between an Hfr strain and an F- strain

c) Conjugation between an F’ strain and an F+ strain

d) The F plasmid undergoes homologous recombination with the chromosome and becomes integrated

e) Conjugation between an F’ strain and an F- strain 5.

In negative regulation of gene expression, what molecule would you expect to find bound to the operator if there is no transcription

? a) RNA polymerase

b) repressor

c) No molecules will be bound to the operator

d) corepressor

e) activator

Answer 1

1). c) a frameshift mutation

A permanent change in the sequence of nucleotides of the genome is called mutation, which results in altered or absence of corresponding protein synthesis. If the base substitution of one with another results in the formation of a stop codon like UAG, the translation process terminates at that point and the resulting protein is short and may be non-functional. These types of mutations are known as nonsense mutations.

Missense mutations occur as a result of base substitutions, but the results are not much disruptive like nonsense mutations (Eg: they do not result in the formation of stop codons).

Insertion or deletion of single base pairs in DNA results in frame shift mutations, in this; the reading frame shifts at the point of mutation and results in non-functional proteins.