MIBO Chapter 8 Flashcards

Questions and Answers

Summarize the three stages of transcription.

Initiation, Elongation, and Termination. Initiation is when RNA binds to the beginning of the gene. Elongation is when the nucleotides are added and the RNA chain elongates. Termination is when the stop codon terminates it.

What is Rifamycin B?

Rifamycin B selectively binds to the bacterial RNA polymerase and inhibits transcription initiation.

What is Actinomycin B?

Actinomycin B non-selectively binds to DNA and inhibits transcription elongation.

What are the six types of RNA found in a cell?

messenger RNA, ribosomal RNA, transfer RNA, small RNA, tmRNA, catalytic RNA. Signup and view all the answers

Draw/diagram a ribosome structure detailing the two subunits of the ribosome and the three binding sites for tRNA.

Ribosomes are composed of two subunits (30s and 50s in prokaryotes), forming the 70s ribosome with three binding sites: A (acceptor) site, P (peptidyl-tRNA) site, and E (exit) site. Signup and view all the answers

Summarize the three stages of protein synthesis.

Initiation brings the two ribosomal subunits together, placing the first amino acid in position. Elongation sequentially adds amino acids as directed by mRNA transcript. Termination releases the completed protein and recycles ribosomal subunits. Signup and view all the answers

What is Streptomycin?

Streptomycin inhibits the 70s ribosome formation by stopping 30S and 50S from coming together. Signup and view all the answers

What is Erythromycin?

Erythromycin inhibits the 70s ribosome formation by stopping 30S and 50S from coming together. Signup and view all the answers

How can transcription and translation happen simultaneously in a bacterial cell?

Different ribosomes can bind simultaneously to the start of each cistron within a polycistronic mRNA, allowing ribosomes to translate protein before RNA polymerase completes the mRNA. Signup and view all the answers

Explain the role of chaperones in protein folding.

Chaperones assist in the folding of many proteins, such as GroEL and GroES which form stacked rings, while DnaK clamps down on polypeptides to assist folding. Signup and view all the answers

Explain the purpose of DNA annotation and how it is used in bioinformatics.

DNA annotation involves understanding the meaning of DNA sequences, using computers to find patterns like regulatory sequences, open-reading frames (ORFs), and rDNA and tRNA genes. Signup and view all the answers

Study Notes

Stages of Transcription

Transcription comprises three stages: Initiation, Elongation, and Termination.
Initiation: RNA polymerase binds to the beginning of a gene.
Elongation: Nucleotides are added, elongating the RNA chain.
Termination: A stop codon signals the end of transcription.

Rifamycin B

Selectively inhibits transcription initiation by binding to bacterial RNA polymerase.

Actinomycin B

Non-selectively binds to DNA, affecting both eukaryotic and prokaryotic cells.
Inhibits the elongation phase of transcription.

Types of RNA

Six types of RNA in a cell include:
- Messenger RNA (mRNA)
- Ribosomal RNA (rRNA)
- Transfer RNA (tRNA)
- Small RNA (sRNA)
- tmRNA
- Catalytic RNA (cRNA)

Ribosome Structure

Ribosomes consist of two subunits containing rRNA and proteins.
Prokaryotic ribosomes have 30S and 50S subunits, forming a 70S ribosome.
The 70S ribosome features three tRNA binding sites:
- A (Accepting): Binds incoming aminoacyl tRNA.
- P (Peptidyl): Holds tRNA with the growing polypeptide chain.
- E (Exit): Binds tRNA recently stripped of its polypeptide.

Stages of Protein Synthesis

Initiation: The first amino acid is positioned as two ribosomal subunits come together.
Elongation: Amino acids are sequentially added based on mRNA instructions.
Termination: Releases the completed protein and recycles ribosomal subunits.
Each stage requires specific protein factors and energy (GTP).

Streptomycin

Inhibits 70S ribosome formation by preventing 30S and 50S subunits from joining.
Resistance can occur through mutation of the S12 gene, allowing ribosome function without streptomycin binding.

Erythromycin

Similar to streptomycin, it prevents the formation of the 70S ribosome.
Resistance mechanisms are analogous, involving the S12 gene mutation.

Coupled Transcription and Translation in Bacteria

Bacterial cells can initiate translation while transcription is still in progress.
Multiple ribosomes can attach to a polycistronic mRNA molecule simultaneously.
This process is termed coupled transcription and translation, contrasting with eukaryotic cells that separate these processes into different compartments.

Role of Chaperones in Protein Folding

Chaperones assist in the folding of many proteins.
Examples include:
- GroEL and GroES: Form stacked rings with a hollow center for polypeptide fitting.
- DnaK: Binds directly to polypeptides without forming rings, aiding in proper folding.

Purpose of DNA Annotation in Bioinformatics

DNA annotation identifies the functional meaning of DNA sequences.
Involves pattern recognition by computers, focusing on regulatory sequences, open-reading frames (ORFs), and rDNA/tRNA genes.
ORFs are crucial as they encode actual polypeptides.
In eukaryotes, ORF identification is complicated by introns present in the gene structure.

Description

Test your knowledge on the key concepts of transcription in molecular biology with this set of flashcards. Learn about the stages of transcription, important inhibitors like Rifamycin B, and more. Perfect for students looking to reinforce their understanding of gene expression.