Unit 6 AP Biology Gene Expression and Regulation

Contrast amount of DNA between prokaryotes and eukaryotes.

• Eukaryotes have multiple DNA strands while prokaryotes have one DNA strand

• Prokaryotes have multiple DNA strands while eukaryotes have one DNA strand

Answer explanation

The DNA structure differs between prokaryotes and eukaryotes. Prokaryotes have a single circular DNA strand while eukaryotes have multiple linear DNA strands. Prokaryotes store theirs in the nucleoid while eukaryotes store theirs in the nucleus.

Which direction is DNA synthesized in DNA replication?

• 3' -> 5’

• 5' -> 3’

• C terminus to N terminus

• N terminus to C terminus

Answer explanation

DNA is antiparallel, so it is synthesized

 5' -> 3’ and read 3' -> 5’. Recall the 5’ end is the phosphate group and the 3’ end is the hydroxyl of the deoxyribose.

Function of Poly A tail...

• Add phosphates to the RNA

• Provide ATP for transcription

• Protect from hydrolytic enzymes 

• Site of ribosome binding 

Answer explanation

The poly-A tail is made up of multiple adenines at the end of the mRNA. As the hydrolytic enzymes in the cytosol hydrolyze the mRNA, it prolongs its "life" in the cytosol to maximize protein synthesized.

In RNA, adenine pairs with...

• Cytosine

• Guanine

• Thymine

• Uracil

Answer explanation

RNA has four nucleotides: adenine, cytosine, guanine, and uracil. Base pairing is Adenine with Uracil and Cytosine with Guanine.

Apples Under the Tree (A-U)

Cars in the Garage (C-G)

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.

What is at the 5’ end of DNA?

• Hydrogen

• Hydroxyl

• Nitrogenous Base

• Phosphate

Answer explanation

The 5’ end has the phosphate group.

The 1’ end has the nitrogenous base.

The 3’ end has the hydroxyl group of the pentose sugar.

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.

Contrast shape of DNA between prokaryotes and eukaryotes.

• Eukaryotes have circular and prokaryotes have linear DNA

• Prokaryotes have circular and eukaryotes have linear DNA

Answer explanation

The DNA structure differs between prokaryotes and eukaryotes. Prokaryotes have a single circular DNA strand while eukaryotes have multiple linear DNA strands. Prokaryotes store theirs in the nucleoid while eukaryotes store theirs in the nucleus.

Enzymes responsible for breaking H bonds between strands

• Helicase

• Ligase

• Polymerase

• Topoisomerase

Answer explanation

The helicase will break the H bonds between the two strands to allow access to the nucleotides for DNA replication. Recall, enzymes tell you what they do… helicase will break the bonds in the helix.

What enzyme is responsible for making the new DNA strand?

• DNA polymerase

• Helicase

• Ligase

• Primase

Answer explanation

DNA polymerase will synthesize the new DNA strand. Recall, enzymes tell you what they do so DNA polymerase makes a DNA polymer.