tRNA, mRNA, rRNA

Transcription

The process of synthesizing RNA from a DNA template, where the DNA sequence is transcribed into messenger RNA (mRNA).

Where does transcription occur in eukaryotes?

In the nucleus of the cell.

Translation

The process of synthesizing proteins from mRNA, where the sequence of nucleotides in mRNA is translated into a sequence of amino acids.

Where does translation occur in eukaryotes?

In the cytoplasm of the cell.

Telomeres

Repetitive nucleotide sequences at the ends of chromosomes that protect them from degradation and prevent fusion with other chromosomes.

Telomerase

An enzyme that adds repetitive nucleotide sequences to the ends of telomeres, helping to maintain chromosome integrity during replication.

What is the function of DNA polymerase III?

To add nucleotides to the 3' end of a growing DNA strand during DNA replication.

How does telomerase replicate the ends of linear chromosomes?

By adding a cap that resists degradation, catalyzing the lengthening of telomeres, and adding GC pairs to maintain chromosome integrity.

Leading Stand

The strand of DNA that is synthesized continuously in the same direction as the movement of the replication fork.

Lagging Strand

The strand of DNA that is synthesized discontinuously in short fragments, which are later joined together.

What is the central dogma of molecular biology?

The framework that describes the flow of genetic information from DNA to RNA to protein.

What are the key differences between RNA and DNA?

RNA is single-stranded, contains ribose sugar instead of deoxyribose, and uses uracil instead of thymine.

Codons

Sequences of three nucleotides in mRNA that correspond to specific amino acids during protein synthesis.

Promoter

A specific DNA sequence that signals the start of transcription and is recognized by RNA polymerase.

Transcription Factor

A protein that helps regulate the transcription of specific genes by binding to nearby DNA.

What is mRNA modification?

The process of altering the mRNA transcript after transcription, including capping, polyadenylation, and splicing.

Exons

The coding regions of a gene that are retained in the final mRNA after splicing.

Introns

The non-coding regions of a gene that are removed during RNA splicing.

tRNA

A type of RNA molecule that helps decode a messenger RNA (mRNA) sequence into a protein by carrying the appropriate amino acid to the ribosome during protein synthesis.

tRNA (function)

To transport specific amino acids to the ribosome during protein synthesis, matching them to the corresponding codon in mRNA.

Wobble Pairing

The flexibility in base pairing at the third position of a codon, allowing for some variation in the genetic code.

Shine-Dalgarno sequence

A ribosomal binding site in prokaryotic mRNA that helps initiate translation.

RNA Polymerase

Synthesizes RNA from a DNA template during transcription.

What is the difference between prokaryotic and eukaryotic transcription?

Eukaryotic transcription involves multiple RNA polymerases and transcription factors, while prokaryotic transcription is simpler and occurs in the cytoplasm.

snRNP

Small nuclear ribonucleoproteins that recognize intron-exon junctions and facilitate splicing in eukaryotic cells.

Translation Termination

The process where the ribosome reaches a stop codon, leading to the release of the newly synthesized polypeptide chain.

What is the evolutionary significance of telomerase in lobsters?

Telomerase activation in lobsters is linked to their ability to maintain long-term cell proliferation and prevent senescence.

What occurs during transcription?

RNA is synthesized from a DNA template.

What amino acid does the tRNA with anticodon CGG correspond to?

Arginine.

What amino acid does the tRNA with anticodon GCC correspond to?

Alanine.

Why are there fewer tRNA molecules than mRNA codons?

The third position of the codon allows flexibility (wobble), enabling some tRNA anticodons to recognize multiple mRNA codons.

What does translation directly require?

mRNA, tRNA, and rRNA.

Why aren't the number of tRNA anticodons equal to mRNA codons?

The third base pair on the tRNA allows flexibility, enabling some tRNA anticodons to recognize more than one mRNA codon.

Which ribosomal site reads a codon during elongation?

The A site.

What are post-translational modifications of proteins?

They may include the addition of carbohydrates to form glycoproteins, removal of introns, addition of a 5' cap, and addition of a poly-A tail.

Where are eukaryotic mRNA molecules modified?

In the nucleus.

What does the 5' cap and 3' poly-A tail do?

They protect mRNA from degradation.

What is the effect of the error-prone reverse transcriptase carried by HIV?

It results in a high mutation rate, leading to rapid evolution of the virus.

What causes high mutation rates in E. coli?

The proofreading mechanism of DNA polymerase was not working properly.

What does it mean when we say the genetic code is redundant?

More than one codon can specify the addition of the same amino acid.

What is the corresponding mRNA codon for the DNA template strand 5' AGT 3'?

3' UCA 5'.

According to the central dogma, what comes after DNA?

mRNA.

How does termination of translation occur?

A stop codon is reached.

What does complementary base pairing in DNA allow?

It permits the specific pairing of adenine with thymine and cytosine with guanine.

What is the process of transcription?

The synthesis of RNA from a DNA template.

How do eukaryotic and prokaryotic codons compare?

Codons are a nearly universal language among all organisms.

What would you expect of a eukaryote lacking telomerase?

A reduction in chromosome length in gametes.

What occurs at the A site of a ribosome?

The A site (Aminoacyl site) of a ribosome is where the charged tRNA, carrying an amino acid, binds during translation, allowing the amino acid to be added to the growing polypeptide chain.

What occurs at the P site of a ribosome?

The P site (Peptidyl site) of a ribosome holds the tRNA that carries the growing polypeptide chain, facilitating the transfer of the polypeptide to the amino acid on the tRNA in the A site.

What occurs at the E site of a ribosome?

The E site (Exit site) of a ribosome is where the empty tRNA exits the ribosome after its amino acid has been added to the polypeptide chain.

What are the stages of translation?

Translation consists of three main stages: initiation (assembly of the ribosome and the start codon), elongation (addition of amino acids to the polypeptide chain), and termination (release of the completed polypeptide when a stop codon is reached).

How does transcription initiation differ from translation initiation?

Transcription initiation involves the binding of RNA polymerase to the promoter region of DNA to synthesize RNA, while translation initiation involves the assembly of the ribosome at the start codon of mRNA to begin protein synthesis.

How are proteins modified after translation?

Proteins are modified after translation through processes such as phosphorylation, glycosylation, and cleavage, which can alter their activity, stability, and localization within the cell.

Where do protein modifications typically occur?

Protein modifications typically occur in the endoplasmic reticulum and Golgi apparatus, where proteins are folded, modified, and sorted for transport to their specific locations in the cell.