molecular genetics test

What is a purine?

A nitrogenous base with a double-ring structure.

What are the two general categories of nitrogenous bases found in DNA and RNA?

Purines and pyrimidines.

Which nitrogenous bases are classified as purines?

Adenine and guanine.

pyramidine

single ring structure (thymine, cytosine, and uracil)

Similarities between purine and pyramidine

both contain high amounts of nitrogen and bond to a sugar and phosphate. they are both also found in dna and rna.

What is capping in mRNA processing?

Capping is the addition of a modified guanosine to the 5' end of mRNA.

Why is capping important for mRNA?

Capping is needed for mRNA to exit the nucleus and bind to ribosomes.

When does capping occur during mRNA synthesis?

Capping happens co-transcriptionally while RNA is still being made.

What role does capping play in mRNA stability?

Capping protects the mRNA from being broken down by enzymes.

What is the poly-A tail?

A string of 200-300 adenine nucleotides added to the 3' end of mRNA.

When does the addition of the poly-A tail occur?

After transcription.

What happens to RNA before the poly-A tail is added?

Enzymes cut the RNA at a specific signal.

What is the purpose of the poly-A tail?

Increases mRNA stability and protects it from degradation.

What is a codon?

A specific sequence of three adjacent bases on a strand of DNA or RNA.

What information does a codon provide?

Genetic code information for a particular amino acid.

What is an anticodon?

A sequence of three bases of a tRNA molecule.

What does an anticodon pair with during protein synthesis?

The complementary three-nucleotide codon of an mRNA molecule.

inducer

A specific small molecule that inactivates the repressor in an operon.

What is a corepressor?

A small molecule that binds to a bacterial repressor protein.

What does a corepressor do to a repressor protein?

It changes the protein's shape.

What is the effect of a corepressor binding to a repressor protein?

It allows the repressor to bind to the operator.

What is the result of a repressor binding to the operator?

It switches an operon off.

What sugar is found in DNA?

Deoxyribose

What is the structure of DNA?

Double stranded (double helix)

What nitrogenous bases are found in DNA?

A, T, G, and C

What sugar is found in RNA?

Ribose

What is the structure of RNA?

Single stranded

What nitrogenous bases are found in RNA?

A, U, G, and C

Who discovered DNA?

Friedrich Miescher

What substance did Friedrich Miescher extract from the nucleus of white blood cells?

An acidic substance with lots of phosphorus

What type of cell did Friedrich Miescher extract DNA from?

White blood cells

Who is Maurice Wilkins?

An English biochemist.

What significant contribution did Maurice Wilkins make to science?

He helped discover the helical structure of DNA.

What technique did Maurice Wilkins use to reveal DNA's helical structure?

X-ray diffraction.

Who are the scientists credited with building the first correct model of the structure of DNA?

James Watson and Francis Crick

What is the structure of DNA that Watson and Crick proposed?

Double helix

What are the components of the DNA structure that Watson and Crick's model included?

Base pairs and antiparallel strands

Stages of DNA replication

Initiation, elongation, termination

What is the lagging strand?

strand that is synthesized in fragments away from the replication fork.

What are Okazaki fragments?

Individual sections used to synthesize the lagging strand.

Why is the lagging strand called 'lagging'?

Because it is synthesized in fragments and lags behind the leading strand.

What is transcription?

Transcription is the process where DNA forms RNA.

What type of RNA is produced during transcription?

mRNA with a nucleotide sequence complementary to one of the DNA strands.

Where does transcription occur in eukaryotic cells?

In the nucleus.

What is translation?

Translation is the process of taking the message from mRNA and making it into a protein.

What components are involved in translation?

mRNA, tRNA, amino acids, and a ribosome.

Where does translation occur in eukaryotic cells?

In the cytoplasm.

What are APE sites?

Crucial binding spots on a ribosome during protein synthesis.

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

It serves as the entry for new tRNA molecules.

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

It holds the growing polypeptide chain.

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

It is where uncharged tRNA exits the ribosome.

What process do APE sites facilitate?

The orderly building of proteins from mRNA instructions.

peptide bond

Bonds that connect amino acids.