Top-down control - Higher trophic levels determine the sizes of the lower trophic levels Bottom-up control - Size of a higher trophic level is determined by lower trophic level 

TLS Online TPP Program

#Id: 3667

#Unit 3. Fundamental Processes

Valyl-tRNA synthetase can sterically exclude isoleucine from its catalytic pocket because isoleucine is larger than valine.

TLS Online TPP Program

#Id: 3668

#Unit 3. Fundamental Processes

The protein-coding region(s) of each mRNA is composed of a contiguous, non-overlapping string of codons called an open reading frame (commonly known as an ORF).

TLS Online TPP Program

#Id: 3669

#Unit 3. Fundamental Processes

Translation starts at the 5’end of the ORF and proceeds one codon at a time to the 3’end. The first and last codons of an ORF are known as the start and stop codons.

TLS Online TPP Program

#Id: 3670

#Unit 3. Fundamental Processes

mRNAs containing multiple ORFs are known as polycistronic mRNAs, and those encoding a single ORF are known as monocistronic mRNAs.

TLS Online TPP Program

#Id: 3671

#Unit 3. Fundamental Processes

A polycistronic prokaryotic message with three ORFs. Each ribosome binding site is indicated by a purple box labeled RBS.

TLS Online TPP Program

#Id: 3672

#Unit 3. Fundamental Processes

A monocistronic eukaryotic message. The 5’cap is indicated by a “ball” at the end of the mRNA.