Final answer:
The yeast Ty retrotransposon synthesizes TyA-B protein through a mechanism that involves several genes including Gag, RT, Prt, and Int, which encode the proteins necessary for forming a virus-like particle (VLP), reverse transcription, protease activity, and genome integration, respectively. The synthesis takes place in virus-like particles in the cytoplasm where reverse-transcribed DNA is then able to reintegrate into the yeast genome.
Step-by-step explanation:
Yeast Ty Retrotransposon Mechanism
The mechanism used by the yeast Ty retrotransposon to synthesize TyA-B protein involves several integrated genes and their respective enzymes that contribute to the retrotransposition process. Firstly, the Gag gene encodes the group-specific antigen, a structural protein that forms a virus-like particle (VLP) which also serves as the enclosure for the reverse-transcribed transposon DNA in the cytoplasm. The RT gene codes for reverse transcriptase responsible for making reverse-transcribed copies from retrotransposon transcript RNAs. Next, the Prt gene encodes a protease that degrades the VLP as the retrotransposon enters the nucleus. The Int gene encodes the integrase needed for integration of the retrotransposon into a genomic DNA insertion site. These proteins all enter the nucleus, where they play a role in integrating and propagating the retrotransposon within the yeast's genome.
During the cycle, VLP encapsulates retrotransposon RNA and proteins in the cytoplasm. Double-stranded reverse transcripts (cDNAs) of the viral RNA are then synthesized within the VLPs. After shedding the VLP coat, the cDNAs can re-enter the nucleus and integrate into the yeast genome, resembling the action of retroviral integration but without causing infection.