BISC 130 - Chapter 15: Genes and Proteins

By Rahul R.

What is the Central Dogma of Molecular Biology?

Describes the flow of information in cells: DNA --> RNA --> Protein.

What enzyme carries out prokaryotic transcription?

RNA Polymerase.

What are the three phases of prokaryotic transcription?

Initiation, Elongation, Termination.

What is a promoter in the context of transcription?

A region of DNA with a specific sequence that allows RNA Polymerase to know where to bind.

In prokaryotic transcription, what does RNA Polymerase do during elongation?

Builds RNA in a 5' to 3' direction using the template strand of DNA.

What is the termination mechanism in prokaryotic transcription?

Rho protein catches up to RNA Polymerase or a hairpin structure forms in RNA, causing transcription to end.

RNA Polymerase builds in what direction?

5’ to 3’ during transcription

What nitrogenous base does RNA lack that DNA has?

RNA doesn’t have a Thymine (T). It has a Uracil (U) instead

What are ways in which Eukaryotic Transcription is different from P. Transcription?

1. There are 3 different RNA Polymerases

2. Introns are removed from the DNA molecule while Exons are fused together

3. RNA is processed, where a 5’ cap and a Poly-A tail is attached to both ends to ensure stability and longer life.

The newly synthesized RNA is complementary to what part of DNA?

The coding strand (the top strand)

What two strands are the exact same, except the differences in Thymine and Uracil?

The coding strand and the new RNA

What are exons?

An expressed sequence that is kept in the RNA after processing.

How are introns treated during eukaryotic transcription?

Introns are spliced out.

What does 'degenerate' mean in the context of the genetic code?

Most amino acids are encoded by multiple codons.

What is a codon?

Any set or combination of 3 nucleotides (ATC, TCA, CGA, GAT)

How many nucleotides encode 1 amino acid?

Three nucleotides and their respective combinations each code for 20 amino acids.

How many possible combinations of those 3 nucleotide pairs (AAA, TAG) are needed for all 20 amino acids?

64 possible combinations are needed for all 20 amino acids; EACH nucleotide (A, T, C, G) has 3 different combinations

Can different combinations of two nucleotide pairs account for all 20 amino acids?

NO. There would only be 16 possible combinations that each encode for 20. So 4 amino acids would be left out/not coded for.

In which type of cell does translation and transcription occur at the same time?

Prokaryotic cells - it occurs in the cytoplasm.

The 3 phases of both translation/transcription are

Initiation, Elongation, and Termination

Where is translation carried out?

In the ribosomes

What is a stop codon?

Signals the end of translation and DOES NOT encode an amino acid. UAA, UAG, and UGA (Stop Codons)

What are the three phases of translation?

Initiation, Elongation, Termination.

What is tRNA (Transfer RNA) and what does it do in Elongation?

Consists of an amino acid and an anticodon; It binds an amino acid to its corresponding codon (nucleotide) on the mRNA.

During termination, what binds to the stop codon in the mRNA to stop the translation?

A release factor protein

What are point mutations?

Changes that affect a single base pair in DNA.

What is a silent mutation?

A mutation that has no effect on the amino acid sequence. It’s usually a mutation that results in a redundant nucleotide encoding the same amino acid.

What is a nonsense mutation?

A mutation that changes a codon encoding an amino acid to a stop codon, thus protein synthesis stops.

What is a frameshift mutation?

Insertion or removal of nucleotides that shifts the reading frame and alters the amino acid sequence.