Ch 8 Adaptive Quiz

Nucleotides are made of:

nucleosides and phosphoryl groups.

Name a rule that determines which bases will pair with its opposing base to form a double helix.

DNA samples from various species have both A:T and C:G ratios of 1:1.

During DNA replication, what is the large protein that corrects mistakes called?

polymerase

tRNA has a cloverleaf structure with many bonds between bases. What types of bonds are they?

hydrogen

How many different stop codons are there for translation?

three

Ribose contains a pentagonal ring, but one of the five atoms in the ring is not a carbon. What type of atom is found at that position in the ring?

an oxygen

Which of these statements best describes what a double helix of DNA is stabilized by?

both hydrogen bonding between base pairs and van der Waals interactions

Which type of RNA is typically found in the greatest abundance in a cell?

rRNA

Which one of the following ions does RNA polymerase require?

Mg²⁺

What purine-rich region of prokaryotic mRNA precedes the initiating codon and base pairs with complementary nucleotides in the ribosomal RNA?

the Shine–Dalgarno sequence

Describe the structure of the bases in the Watson-Crick model of DNA.

The bases are nearly perpendicular to the helix axis.

A primer containing what kind of free group is required to begin DNA synthesis?

3′-OH

What is TRUE regarding prokaryotic ribosomes and/or rRNA?

rRNA serves as the catalyst in protein synthesis.

A comparison of the three different forms of double-stranded DNA reveals which has the largest pitch per turn of the helix?

Z-DNA

A comparison of the three different forms of double-stranded DNA reveals which has the widest diameter?

A-DNA

Which one of the following serves as the nucleophilic attacker in the DNA polymerase mechanism of action?

the 3′ hydroxyl group of the primer

What does the +1 site of a gene indicate?

the location of the first nucleotide to be transcribed

Which position in a ribose molecule does not have a hydroxyl group?

the 4′ carbon

Which of the following enzymatic activities is sometimes associated with DNA polymerases, and why is the activity important?

nuclease, because it increases the fidelity of replication

Of the different strands of double-stranded DNA, which one has more base pairs per turn of the helix?

Z-DNA

Of the different strands of double-stranded DNA, which one has the smallest tilt of base pairs from perpendicular to helix axis?

B-DNA

What are the "activated precursors" for RNA polymerase?

All four ribonucleoside triphosphates — ATP, GTP, UTP, and CTP

What does small nuclear RNA (snRNA) do?

This type of RNA can form large complexes with proteins to create spliceosomes that facilitate splicing.

Most synonymous codons differ:

only in the last base of the triplet.

What does the Shine-Delgarno sequence do?

This sequence differentiates the initiating AUG codon from internal AUG codons in prokaryotes.

What is the purpose of transfer RNA?

It decodes the template for protein synthesis

What is the principle behind Chargaff's rules?

Complementary bases are equally abundant, but the abundance of non-complementary bases varies based on the species' DNA sequence.

Which one of the following best indicates the expected net charge on an ATP molecule?

−4

A tRNA molecule carries an amino acid in an activated form to the ribosome. The carboxyl group of this amino acid is esterified by which group?

hydroxyl

Cells need to unwind DNA each time they copy it. How do they achieve this?

through the use of proteins known as helicases

How do DNA polymerases prevent mistakes during DNA synthesis?

Nuclease activity allows polymerases to fix mismatched bases.