DNA Transcription and Translation - NRSG 305

What occurs before cell division?

DNA replication

What is the process of forming RNA for protein synthesis called?

DNA Transcription

What does it mean when a gene is 'expressed'?

It means the cell makes a protein based on that gene.

How do muscle cells differ from liver cells in terms of protein synthesis?

Each type of cell makes only the kinds of proteins it needs.

What is the central dogma of molecular biology?

DNA directs protein synthesis through the processes of transcription and translation.

What is the role of a ribosome in protein synthesis?

It is the site of translation where polypeptides are synthesized.

What is the sequence of events in protein synthesis?

DNA → RNA → protein

What is produced during transcription?

mRNA (messenger RNA) is synthesized from DNA.

What is produced from Translation?

Polypeptide, occurs in ribosomes in the cytosol

What is the main difference between prokaryotic and eukaryotic transcription?

In prokaryotes, transcription and translation occur together; in eukaryotes, transcription occurs in the nucleus and mRNA is processed before translation.

What is pre-mRNA?

It is the initial RNA transcript that undergoes processing to become mRNA.

What happens during RNA processing in eukaryotic cells?

Pre-mRNA is modified by adding a 5' cap and a poly-A tail, and introns are removed.

What is the function of the 5' cap added to mRNA?

It helps export mRNA to the cytosol, protects it from degradation, and aids ribosome attachment.

What is the role of spliceosomes in RNA processing?

They remove introns and join exons together in the mRNA transcript.

What are introns and exons?

Introns are non-coding sequences, while exons are coding sequences that are expressed.

What is the significance of alternative RNA splicing?

It increases the number of different proteins that can be produced from a single gene.

What is the role of tRNA in translation?

tRNA carries amino acids to the ribosome and matches its anticodon with the codon on mRNA.

What is a codon?

A triplet sequence of bases along mRNA that codes for an amino acid or a stop signal.

How many bases code for each amino acid?

Three bases (one codon) code for each amino acid.

What is the process of termination in transcription?

The RNA transcript is released, and RNA polymerase detaches from the DNA.

What is the function of RNA polymerase during transcription?

It unwinds the DNA and synthesizes RNA by adding nucleotides according to base-pairing rules.

What is the TATA box?

A promoter sequence that signals the initiation of transcription in eukaryotic cells.

What is the difference between the template strand and the non-template strand of DNA?

The template strand is used to synthesize RNA, while the non-template strand is not directly involved in transcription.

What happens during the elongation stage of transcription?

RNA polymerase moves downstream, unwinding DNA and elongating the RNA transcript.

What is the role of transcription factors in eukaryotic transcription?

They help RNA polymerase recognize promoter sequences and initiate transcription.

What is the polyadenylation signal?

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

What is the significance of the 3' UTR in mRNA?

It is the untranslated region that may play roles in regulation of translation and mRNA stability.

What are ribozymes?

Catalytic RNA molecules that can splice RNA and function as enzymes.

What is the relationship between bases and amino acids in genetic coding?

One base corresponds to one amino acid; two bases correspond to one amino acid with 16 combinations; three bases correspond to one amino acid with 64 combinations.

What is the genetic universal code?

It is the set of rules by which information encoded in genetic material is translated into proteins, applicable from bacteria to humans.

What are the four bases of mRNA?

Adenine (A), Uracil (U), Cytosine (C), and Guanine (G).

What does the codon UAU code for?

Tyrosine (Tyr).

What does the codon UUU code for?

Phenylalanine (Phe).

What does the codon UGA signify?

It is a stop codon.

Which amino acid does AUG code for?

Methionine (Met) or serves as the start codon.

What is the function of transfer RNA (tRNA)?

tRNA shuttles amino acids to the ribosome for polypeptide synthesis.

What is the structure of tRNA?

tRNA has a two-dimensional L-shaped structure with an anticodon and an amino acid attachment site.

What are the three binding sites of a ribosome?

The A site (Aminoacyl-tRNA binding site), P site (Peptidyl-tRNA binding site), and E site (Exit site).

What are the three stages of translation?

Initiation, elongation, and termination.

What occurs during the initiation stage of translation?

The mRNA, initiator tRNA, and ribosomal subunits come together at the start codon.

What happens during the elongation stage of translation?

Amino acids are added one by one to the growing polypeptide chain.

What is the role of the release factor in translation?

It binds to the stop codon, triggering the release of the completed polypeptide.

What is a polyribosome?

A cluster of ribosomes translating a single mRNA molecule simultaneously.

What is the significance of mutations in the genetic code?

Mutations can lead to changes in amino acids, potentially resulting in dysfunctional proteins.

What is the function of aminoacyl-tRNA synthetase?

It attaches the correct amino acid to its corresponding tRNA.

What is the process of RNA processing in eukaryotes?

The RNA transcript (pre-mRNA) is spliced and modified to produce mature mRNA before it exits the nucleus.

What is epigenetics?

Chemical mechanisms that control the expression of genes, such as methylation and histone modification.

What is the wobble position in codons?

It is the third base of a codon that can vary without changing the amino acid specified.

What is the role of signal recognition particle (SRP) in protein synthesis?

SRP guides the ribosome to the endoplasmic reticulum for protein export.

What is the significance of the start codon?

It signals the beginning of translation and codes for the amino acid methionine.

What is the function of ribosomes?

Ribosomes facilitate the coupling of tRNA anticodons with mRNA codons during protein synthesis.

RNA polymerase

The enzyme responsible for RNA transcription.

How many of the DNA strands is read during transcription?

Only one strand is read.

RNA polymerase function

It pries the DNA strands apart.

Nucleotides in RNA

RNA polymerase adds nucleotides to build the RNA molecule.

Base-pairing rule in RNA

Uracil (U) replaces thymine (T).

Three stages of RNA transcript synthesis

Initiation, Elongation, and Termination.

Role of the promoter in transcription

It signals the start point for RNA synthesis.

What helps eukaryotic RNA polymerase recognize promoter sequences

Transcription factors.

What is formed when RNA polymerase and transcription factors assemble at the promoter

The transcription initiation complex.

What happens after RNA polymerase binds to the promoter during initiation

DNA strands unwind, and RNA synthesis begins at the start point.

Direction in which RNA polymerase builds the RNA transcript during elongation

5′ → 3′ direction.

Number of bases of DNA exposed at a time during elongation

About 10-20 bases.

What happens to the DNA after RNA polymerase passes through it during elongation

The DNA strands re-form a double helix.

How termination occurs in prokaryotes

A terminator sequence signals polymerase to detach.

How termination occurs in eukaryotes

RNA polymerase transcribes the polyadenylation sequence (AAUAAA), proteins cut the RNA free, and polymerase eventually falls off.

Why are introns important?

Allows an increase in numbers of different proteins possible