Molecular Biology and Genetic Expression

This set of flashcards helps you review key molecular biology concepts, focusing on DNA/RNA processes, mutations, and protein synthesis.

What is the 3’ tail (poly-A tail) and its function in eukaryotes?

Added to the 3’ end of pre-mRNA, it promotes mRNA export, protects from degradation, and is not translated.

What is the purpose of the 5’ cap added to pre-mRNA?

It promotes mRNA export from the nucleus, protects from degradation, and aids ribosome attachment.

In which direction is mRNA synthesized during transcription?

5’ → 3’ direction.

What does the A site on a ribosome do?

It's where the tRNA with the amino acid enters during elongation.

What is the initiation codon in mRNA and what does it code for?

AUG, which codes for Methionine.

What is the Central Dogma of gene expression?

DNA directs the synthesis of proteins.

What is the role of circular DNA in prokaryotes?

It typically has only one origin of replication.

What are codons?

Three-nucleotide sequences on mRNA that correspond to amino acids.

What is a deletion mutation?

A type of Point Mutation involving the removal of nucleotide pairs.

What molecule directs protein synthesis in eukaryotes?

DNA, through the processes of transcription and translation.

What is DNA ligase and its function?

An enzyme that joins Okazaki fragments during DNA synthesis and seals ends during repair.

What does DNA Polymerase III do during DNA replication?

Binds to the primer and adds new DNA nucleotides to the 3' end.

What is alternative splicing?

A process enhancing protein diversity by removing introns and joining exons.

What are exons?

Coding regions in pre-mRNA that remain after splicing and will become proteins.

What mutation is caused by insertion or deletion?

Frameshift mutation.

What does the cytoplasm contain that is essential for translation?

Ribosomes.

How does a missense mutation affect protein synthesis?

It alters the amino acid coded for by a codon.

What is the function of RNA Polymerase?

It synthesizes mRNA from DNA during transcription.

What does telomerase do?

Catalyzes the lengthening of telomeres in germ cells.

What are Okazaki fragments?

Short DNA segments synthesized on the lagging strand during DNA replication.

What type of mutation changes an amino acid codon to a stop codon?

Nonsense mutation.

What is the template used during transcription?

DNA is used to create mRNA.

What is the role of single-strand binding proteins?

They stabilize separated parent DNA strands during replication.

What occurs during the elongation step of transcription?

RNA Polymerase synthesizes the mRNA strand by adding nucleotides.

What modifies mRNA after transcription in eukaryotes?

5’ cap, 3’ tail, and RNA splicing.

What is a peptide bond?

A bond that forms between amino acids during translation.

What causes over-winding in DNA during replication?

The unwinding by helicase creates strain.

What does the Spliceosome complex do?

Accomplishes RNA splicing and contributes to protein diversity.

Where does transcription occur in eukaryotes?

In the nucleus.

What happens during translation termination?

A Stop codon in the A site releases the polypeptide and disassembles ribosomal units.

What does the reading frame refer to?

The correct order of codons on mRNA that must be read for proper translation.

What is redundancy in the genetic code?

The phenomenon where multiple codons can code for the same amino acid.

What enzyme unwinds the DNA double helix at the origins of replication?

Helicase.

What does the rough endoplasmic reticulum (RER) do?

Supports polypeptide folding and protein export from the cell.

How does the transcription initiation complex form?

Transcription Factors bind to the promoter region with RNA Polymerase.

What is the structure of ribosomes?

Composed of rRNA and proteins with a large and small subunit.

What is the purpose of a primer during DNA replication?

Provides a 3' end for DNA polymerase to begin adding nucleotides.

What does termination sequence lead to in prokaryotes?

It causes RNA Polymerase to detach from the DNA.

What is the significance of the TATA box?

It is part of the promoter region in eukaryotes.

What aids the transportation of processed mRNA from the nucleus?

The 5' cap and 3' poly-A tail.

What role does the release factor play during translation?

It binds to Stop codons to terminate translation.

What do introns refer to?

Non-coding regions in pre-mRNA that are removed during splicing.

What are point mutations?

Mutations involving changes in a single nucleotide pair.

How does the genetic code ensure accuracy during translation?

Ribosomes read non-overlapping codons.

What role do chaperonin proteins play?

Assist in the 3D folding of polypeptides.

What does RNA splicing accomplish?

Removes introns and joins exons in mRNA processing.

What is the difference between prokaryotic and eukaryotic transcription initiation?

Prokaryotes use RNA Polymerase directly at the promoter, while eukaryotes involve Transcription Factors.

What do telomeres do?

Protect chromosome ends from shortening during replication.

What defines the lagging strand during DNA replication?

It is synthesized discontinuously in short fragments.

What is the role of DNA Polymerase I?

Removes RNA primers and replaces them with DNA nucleotides.

What causes silent mutations?

Nucleotide substitution that does not alter the amino acid sequence.

What is the function of topoisomerase?

Relieves over-winding strain ahead of the replication fork.

What determines the fate of mRNA in eukaryotic cells?

Post-transcriptional modifications like splicing and capping.

What is the function of the E site on a ribosome?

The exit site where the empty tRNA leaves the ribosome.

How does DNA polymerase III contribute to DNA fidelity?

Through proofreading during DNA synthesis, correcting most errors.

What is the difference between coding and non-coding regions of DNA?

Coding regions (exons) will translate into proteins, while non-coding regions (introns) do not.

How do mutations contribute to genetic diversity?

They can create variations in protein structure and function.

What is the role of the nuclear pore in mRNA processing?

It allows processed mRNA to exit the nucleus to enter cytoplasm.

What distinguishes eukaryotic DNA replication from prokaryotic?

Eukaryotes undergo many short replication origins and involve more complex machinery.