Question

what does the polymerase chain reaction (PCR) accomplish?

1) PCR converts RNA to DNA

2) PCR corrects mutation in a gene

3) PCR makes many copies of DNA segment

4) PCR joins short segments of DNA to make one long segment

how does the ribosome select the next amino acid to add to a growing polypeptide chain?

1) the ribosome selects the amino acid that can form hydrogen bonds with the mRNA

2) the ribosome selects a tRNA that base-pairs with a codon

3) the ribosome senses that the amino acid fits into a binding pocket on the ribosome

4) the ribosome sense that the amino acid has the same codon as the DNA

Answer 1

Answer 1: The Correct answer is option (3) i.e. PCR makes many copies of DNA segment. Polymerase chain reaction is an important method having numerous uses. The basic principle the technique use is to add nucleotides on the template at a rapid rate. Even a small sample of DNA can be taken and makes millions of copy of the same sample. So that it can be easily handled by the user. It doesn't convert RNA to DNA. Denaturation, annealing and extension are the common steps of PCR.

Answer 2: The Correct option is (2) i.e. the ribosome selects a tRNA that base pairs with the codon. Elongation step of translation is a cyclic process on the ribosome. Here, one amino acid is added at a time to the nascent peptide chain. The peptide sequence is determined by the order of codons in mRNA. Ribosome elongate this chain in three stages: Decoding, Transpeptidation and Translocation. During decoding, ribosome selects and binds a charged tRNA whose anticodon is complementary to the mRNA codon in A site. During Transpeptidation, peptidyl group on P site of tRNA is transferred to the aminoacyl group in A site and form peptide bond.