From DNA to Protein – The Middle Molecule

Flashcards based on key concepts from the lecture notes covering the central dogma of molecular biology, transcription, RNA types, and gene regulation.

What does the central dogma of molecular biology describe?

The flow of genetic information from DNA to RNA to protein.

What is the role of mRNA in the process of transcription?

mRNA serves as a transcript (RNA copy) of a gene.

What type of RNA translates mRNA into amino acids?

Transfer RNA (tRNA).

In eukaryotic cells, what is the intervening step called where pre-mRNA is processed into active mRNA?

RNA processing.

What is a gene?

An organized unit of DNA sequences that enables a segment of DNA to be transcribed into RNA.

What is an operon?

A cluster of genes under transcriptional control of one promoter.

How does the lac operon function when lactose is absent?

The lac repressor binds to the operator, preventing transcription.

What is the function of a eukaryotic TATA box?

It is a sequence found in the core promoter that helps initiate transcription.

What is the role of transcription factors in gene regulation?

They bind to DNA near the start of transcription and can either inhibit or assist RNA polymerase.

What is alternative splicing?

A process that allows a single gene to produce multiple mRNA variants by splicing in different ways.

How do miRNAs affect mRNA?

They can silence the expression of pre-existing mRNAs.

What are CRISPR and how do they function in bacteria?

CRISPR loci contain segments derived from bacteriophage DNA and are involved in genome defense by guiding endonucleases to foreign DNA.

What is the relationship between histone acetylation and gene expression?

Histone acetylation generally loosens chromatin structure, which enhances gene expression.

What is the consequence of DNA methylation on transcription?

Methylation typically inhibits transcription by preventing activators from binding or by condensing chromatin structure.

What is the main difference between prokaryotic and eukaryotic transcription regarding RNA polymerases?

Prokaryotes use a single RNA polymerase type for all RNA synthesis, while eukaryotes have three different RNA polymerases for different RNA types.

What are the two types of control mechanisms in gene regulation?

Negative control (repressors inhibit transcription) and positive control (activators enhance transcription).

What is translation in relation to transcription?

Translation is the process that follows transcription, where the mRNA is decoded to build a protein.

What is a spliceosome?

A spliceosome is a complex of proteins and RNA that removes introns from pre-mRNA during RNA splicing.

What are introns and exons?

Introns are non-coding segments of RNA that are removed during splicing, while exons are coding segments that remain in the mature mRNA.

What is the purpose of a 5' cap in mRNA?

The 5' cap protects mRNA from degradation and assists in ribosome binding during translation.

What is the role of the poly-A tail in mRNA?

The poly-A tail enhances the stability of mRNA and aids in its export from the nucleus.

What is the difference between prokaryotic and eukaryotic transcription?

In prokaryotes, transcription occurs in the cytoplasm and is coupled with translation; in eukaryotes, it occurs in the nucleus and involves RNA processing before translation.

What is a transcription factor?

Transcription factors are proteins that help regulate the transcription of specific genes by binding to nearby DNA.

What is the difference between negative and positive regulation in transcription?

Negative regulation involves repressors that inhibit transcription, while positive regulation involves activators that enhance transcription.

What are enhancers and silencers?

Enhancers are DNA sequences that increase transcription levels, while silencers decrease transcription levels.

What is the significance of the TATA box?

The TATA box is a DNA sequence found in the promoter region that is essential for initiating transcription.

What is the purpose of RNA processing?

RNA processing modifies the primary RNA transcript (pre-mRNA) into a mature mRNA molecule through capping, polyadenylation, and splicing.

What is the role of ribosomes in translation?

Ribosomes are the cellular machinery that synthesize proteins by facilitating the translation of mRNA into amino acid sequences.

What is the role of the sigma factor in transcription?

The sigma factor is a protein that helps RNA polymerase bind to the promoter region to initiate transcription in prokaryotes.

What are codons?

Codons are sequences of three nucleotides in mRNA that specify a particular amino acid during translation.

What is the significance of the genetic code?

The genetic code defines the relationship between nucleotide sequences in mRNA and the corresponding amino acids in proteins.

What is the function of tRNA?

Transfer RNA (tRNA) transports specific amino acids to the ribosome during translation based on the codon sequence of the mRNA.

What is the purpose of initiation factors in translation?

Initiation factors are proteins that facilitate the assembly of the ribosome and the start of translation.

What role do chaperone proteins play in protein synthesis?

Chaperone proteins assist in the proper folding and assembly of newly synthesized proteins.

What is the role of the polyadenylation signal?

The polyadenylation signal is a sequence in the pre-mRNA that signals the addition of the poly-A tail and termination of transcription.

What are polypeptides?

Polypeptides are chains of amino acids linked by peptide bonds, which fold into proteins after translation.

What is the difference between the sense strand and the template strand in DNA?

The sense strand (coding strand) has the same sequence as the mRNA (except for uracil), while the template strand is complementary to the mRNA and is used during transcription.

What is the role of release factors in translation?

Release factors are proteins that recognize stop codons and promote the release of the newly synthesized polypeptide from the ribosome.

What are ribozymes?

Ribozymes are RNA molecules capable of catalyzing chemical reactions, including the splicing of introns during mRNA processing.

What is alternative splicing?

Alternative splicing is a regulatory mechanism that enables a single gene to produce multiple protein isoforms by including or excluding certain exons.