Question

1. The 21st and 22nd amino acids found in proteins are the rare amino acids ______________ and ______________.
2. ________________ are nonviral genetic elements that have reverse transcriptase activity.
3. An example of retrotransposons in the human genome is the ____ family of sequences.

Answer 1

1. Answer- The 21st and 22nd amino acids found in proteins are the rare amino acids selenocysteine (Sec) and pyrrolysine (Pyl) .

Explanation- selenocysteine and pyrrolysine are two amino acids that are rarely found in proteins. There are 20 standard amino acids found in proteins and selenocysteine is 21st and pyrrolysine is 22nd amino acid rarely found in proteins.

2. Answer- Retrotransposons are nonviral genetic elements that have reverse transcriptase activity.

Explanation- retrotransposons are transposable elements that copy and paste itself into genome at different site. The retrotransposons has gene for reverse transcriptase and when retroposon is transcribed into mRNA, then reverse transcriptase is synthesized by translation that synthesizes DNA from mRNA and integrates transposon to another site. So that Retrotransposons are nonviral genetic elements that has reverse transcriptase activity.

3.Answer- An example of retrotransposons in the human genome is the Long interspersed nuclear elements (LINEs) family of sequences.

Explanation- The long interspersed nuclear elements i. e. LINEs are family of sequences that are about 7,000 base pairs long and these LINEs are transcribed into mRNA that are translated into enzyme known as reverse transcriptase. Due to reverse transcriptase activity of enzyme, mRNA of LINE used as substrate to synthesize LINE DNA copy and this DNA is integrated into genome at different site.