Molecular Biology Quiz

Histones and DNA Charge

• Histones have a positive charge, which helps their interaction with DNA, which has a negative charge.

tRNA Structure and Codon Pairing

• tRNA molecules have stems and loops.
• The anticodon loop of tRNA pairs with a codon on mRNA.
• At least one, or possibly two, bases on the anticodon loop must pair exactly with the bases of the codon, due to the wobble position.

DNA Polymerase Requirements

• DNA polymerases need a primer, template DNA, and deoxynucleoside triphosphates (dNTPs) to synthesize DNA.

E. coli Genetic Material

• The genetic material in E. coli is composed of circular, double-stranded DNA.

Avery, MacLeod, and McCarty Experiment

• The DNase treatment, used by Avery, MacLeod, and McCarty, allowed them to isolate pure DNA samples.
• It demonstrated that removing DNA prevents transformation.

Adenine Content and G+C Percentage

• If DNA has a 25% adenine content, the G+C content will be 50%.

Introns

• Introns are removed from primary mRNA before translation.
• Introns form a lariat structure during splicing.
• Introns have specific nucleotide sequences at their 5' and 3' ends.

Griffith's 1928 Experiment

• Griffith's experiment demonstrated genetic transformation of non-virulent bacteria into virulent bacteria.
• Mice injected with a mixture of dead virulent bacteria and live non-virulent bacteria died.

Eukaryotic Chromosome Compaction

• Eukaryotic chromosomes involve the formation of nucleosomes, a 30nm fiber, and further compaction of radial loops.

Promoter Region

• The promoter region in a gene contains cis-acting sequences and consensus sequences for RNA polymerase binding.

DNA Replication

• Single-stranded binding proteins maintain the DNA template "open" during replication.
• DNA polymerases are also involved.

RNA

• tRNA is an RNA molecule that is encoded by tRNA genes.
• It is translated into protein in the cytoplasm.
• tRNA has secondary structure and an amino acid accepting site.

Genetic Code

• The genetic code can have multiple (more than one) codons that code for a single amino acid.
• Multiple start codons may exist.
• The genetic code is ambiguous when the same codon codes for two or more amino acids.

RNA Polymerase

• RNA polymerase needs a promoter sequence for binding to initiate transcription and synthesize mRNA.
• Sigma factor helps RNA polymerase find and bind to promoter elements.

RNA Polymerase and DNA

• RNA polymerase is responsible for transcribing DNA into RNA.
• It does not require a primer to synthesize in the 5' to 3' direction.
• RNA polymerase uses ribonucleotides as substrate.

DNA Polymerases

• DNA polymerases require a primer and template for replication to start.

Mutations and DNA Synthesis

• DNA mutations in polymerases may affect the directional synthesis of DNA (the 3' to 5' direction).

Telomerase

• Telomerase synthesizes telomeric repeats at the ends of chromosomes.
• It uses RNA as a template for DNA synthesis.
• It binds to the 3’ overhang of the telomere.

Replication Fork

• DNA replication occurs at a replication fork.

Splicing in Prokaryotes and Eukaryotes

• Splicing of transcripts occurs in the nucleus of eukaryotes but not in the cytoplasm of prokaryotes.

Telomere Mutations

• Mutations in telomerase result in a gradual decrease of chromosome length during cell division.

Transcription Factors

• General transcription factors in eukaryotes recognize the TATA box and recruit RNA polymerase II.

Spliceosome and Introns

• The spliceosome removes introns from primary mRNA.
• The spliceosome recognizes nucleotides within the introns, forming a lariat structure during splicing.

DNA Replication and RNA Enzymes

• RNA polymerases copy genetic information during DNA replication, using RNA-based primers where applicable.

Eukaryotic mRNA Structure

• Eukaryotic mRNA is capped at the 5' end to protect it and aid in transport from the nucleus.

mRNA Translation

• A critical part of mRNA involved in translation is the 5' cap.

Eukaryotic Gene Regulation

• Eukaryotic genes have a large number of introns, that interrupt the coding sequences of exons.
• This contributes to the vast number and diversity in gene products from a relatively lower number of genes.