AP Bio Insta-Review Topic 6.3*: Transcription & RNA Processing

Which RNA functions as site of protein synthesis?

• mRNA

• rRNA

• tRNA

Answer explanation

rRNA is the ribosomal RNA. Ribosomes, the site of protein synthesis, is composed of protein and rRNA.

Which RNA functions to bring amino acids to the ribosome?

• mRNA

• rRNA

• tRNA

Answer explanation

tRNA is the transfer RNA. There are two important binding sites on the tRNAs. At one end, the tRNA is bound to an amino acid and the other end has an anticodon which pairs with the codon on the mRNA.

Which RNA is the transcript from DNA template?

• mRNA

• rRNA

• tRNA

Answer explanation

mRNA is messenger RNA. It functions as a transcript of the DNA to carry the genetic code to the ribosome for protein synthesis.

Which RNA has an anticodon that pairs with codon?

• mRNA

• rRNA

• tRNA

Answer explanation

tRNA is the transfer RNA. The main function of the tRNA is the bring amino acids to the ribosome. The tRNA has an anticodon that pairs with the mRNA codon to ensure the correct amino acid is added.

Which RNA has the codons sequence for translation?

• mRNA

• rRNA

• tRNA

Answer explanation

mRNA is the messenger RNA. It is a transcript of the DNA to carry to message to the ribosome for protein synthesis. The triplet code of nucleotides on the mRNA is called a codon.

Big picture, how do the three different RNA molecules work together?

Answer explanation

mRNA is the product of transcription in the nucleus. It brings the "message" from the nucleus about the order for protein synthesis. mRNA binds to the small subunit of the ribosome.

tRNA brings the amino acids The tRNA has an anticodon at one end that base pairs with the codons on the mRNA and an amino acid on the other end. It binds to the large subunit of the ribosome.

rRNA is the site of protein synthesis. The rRNA binds with protein to form the ribosome. 

How does the location of transcription differ in prokaryotes vs. eukaryotes?

Answer explanation

Due to the absence of a nuclear envelope, transcription occurs in the cytosol (nucleoid) of the prokaryote. 

Due to the presence of a nuclear envelope, transcription occurs in the nucleus of an eukaryote.

Which enzyme is responsible for transcription?

• Ligase

• Primase

• RNA Polymerase

• Transcriptase

Answer explanation

RNA Polymerase is an enzyme that binds to the DNA and synthesizes a RNA strand. Remember: enzymes tell you what they do. RNA Polymerase makes an RNA polymer.

What is the name of the strand read for transcription?

Answer explanation

› Template strand 

› Noncoding strand

› Minus strand 

› Antisense strand 

(Note: you should know all 4 of these terms as they are directly in the CED and can be used in the prompt.)

In transcription, which direction is DNA read?

• 3' to 5’

• 5' to 3’ 

• C terminus to N terminus

• N terminus to C terminus

Answer explanation

DNA and RNA are antiparallel. The DNA is read 3' to 5’ while the RNA is synthesized 5’ to 3’. Remember the 3’ is the hydroxyl group of the pentose sugar and the 5’ is the phosphate.