Genomes and the Flow of Biological Information – QA Flashcards

Flashcards covering the Central Dogma, DNA structure and replication, transcription, translation, cellular organization differences (prokaryotes vs eukaryotes), and mutations as described in the notes.

What is the Central Dogma of Molecular Biology?

The unidirectional flow of genetic information from DNA to RNA to protein, via transcription and translation, with noted exceptions to be learned.

Name the four nucleotides found in DNA and their bases.

Guanine (G), Adenine (A), Thymine (T), and Cytosine (C).

How are DNA strands oriented in the double helix?

They are anti-parallel, running in opposite directions (one strand 5′→3′ and the other 3′→5′).

What base-pairing rules hold in DNA?

A pairs with T, and C pairs with G.

What does DNA replication produce from one original molecule?

Two identical double-stranded DNA molecules, produced via semi-conservative replication using the old strands as templates.

What are the three key steps in genome transmission to daughter cells?

Replication, segregation, and transfer of copies into new cells after division.

Which three RNA types are central to gene expression?

mRNA, tRNA, and rRNA.

What is transcription?

Copying a DNA segment into RNA using RNA polymerase; RNA contains uracil instead of thymine and is processed to its final form.

What is the role of RNA polymerase in transcription?

It uses a DNA template strand to synthesize a complementary RNA strand.

What is the primary transcript and how is it related to final RNA?

The initial RNA product from transcription that is processed to form the final mature RNA.

What are the three major RNA types involved in translation, and what do they do?

mRNA carries the protein-coding sequence; tRNA reads codons and brings amino acids; rRNA forms ribosomes with proteins to catalyze protein synthesis.

How many amino acids are encoded and what are typical protein lengths?

20 amino acids; proteins typically range from ~100 to ~1,000 amino acids (some shorter or longer).

What is translation?

Decoding mRNA into a polypeptide chain on the ribosome.

What is a codon, and what does it encode?

A triplet of nucleotides in mRNA that encodes one amino acid.

What is the role of tRNA during translation?

tRNA decodes codons by delivering the cognate amino acids to the growing polypeptide chain.

What is the start codon and which amino acid is typically added first?

AUG; typically codes for methionine, though Met can occur internally as well.

What are stop codons and what is their function?

Three stop codons that signal termination of protein synthesis.

How is the genetic code read during translation?

In non-overlapping base triplets (codons).

What is the difference between prokaryotic and eukaryotic transcription/translation regarding cellular organization?

Prokaryotes lack a nucleus; transcription and translation can occur simultaneously, and transcripts may be polycistronic. Eukaryotes have a nucleus; transcription occurs in the nucleus, translation in the cytoplasm, and mRNA must be exported.

Where does translation occur in the cell?

In the cytoplasm on ribosomes; prokaryotes initiate translation with transcription, while eukaryotes translate after mRNA export to the cytoplasm.

What is a mutation, in basic terms?

A change in DNA sequence, which can include point mutations, insertions, deletions, and rearrangements.

What is a missense mutation?

A point mutation that changes the encoded amino acid, potentially altering protein function.

What is a nonsense mutation?

A point mutation that introduces a premature stop codon, truncating the protein.

What is a silent mutation?

A mutation that does not change the amino acid sequence and often has no effect.

What is a null (loss-of-function) mutation?

A mutation that eliminates the function of a gene.

What does polycistronic transcription mean in prokaryotes?

A single RNA transcript that encodes multiple genes.