Question

Which of the following is not true of cDNA produced using human brain tissue as the starting material?

(A) It can be amplified by the polymerase chain reaction.

(B) It was produced from pre-mRNA using reverse transcriptase.

(C) It can be labeled and used as a probe to detect genes expressed in the brain.

(D) It lacks the introns of the pre-mRNA.

Short answer

(A) The statement “It can be amplified by the polymerase chain reaction.” is false.

(B) The statement “It was produced from pre-mRNA using reverse transcriptase.” is false.

(C) The statement “It can be labeled and used as a probe to detect genes expressed in the brain.” is true.

(D) The statement “It lacks the introns of the pre-mRNA” is false.

Step-by-step solution

Reverse transcription

The process by which cDNA (complementary DNA) is synthesized from an RNA template using reverse transcriptase is called reverse transcription. Thus, it is also known as RNA-directed DNA polymerase.

Explanation for option “A”

The polymerase chain reaction is used to produce clones of genes. In a polymerase chain reaction, multiple copies of the target DNA sequence are produced. cDNA made from human tissue is DNA and can be amplified.

Thus, cDNA can be amplified by polymerase chain reaction.

Therefore, the given statement is true, and thus the option is false.

Explanation for option “B”

The human gene is converted into mRNA in reverse transcription, which is then transcribed by reverse transcriptase to produce cDNA.

Thus, cDNA can be produced from mRNA through reverse transcriptase.

Therefore, the given statement is true, and thus, the option is false.

Explanation for option “C”

cDNA made from human tissue are used as probes to detect genes in the brain, but they are not labeled.

Thus, cDNA from human tissue cannot be labeled.

Therefore, the given statement is not true, and thus the option is correct.

Explanation for option “D”

All pre-mRNA undergoes slicing in which introns are removed to yield mature mRNA. The mature mRNA is then transcribed into cDNA, which does not contain introns.

Thus, cDNA lacks introns of pre-mRNA.

Therefore, the given statement is true, and thus the option is false.