Unit 2: section 4. Chapter 11: Mechanism of Microbial Genetics

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the central dogma of molecular biology?

DNA -> Protein -> RNA

RNA -> DNA -> Protein

Protein -> RNA -> DNA

DNA -> RNA -> Protein (correct)

Which component is involved in the process of transcription?

DNA polymerase

RNA polymerase (correct)

Ribosomes

DNA ligase

How do prokaryotic and eukaryotic replication differ?

Eukaryotes replicate linear chromosomes. (correct)

Eukaryotes have a single origin of replication.

Prokaryotes have multiple origins of replication.

Prokaryotes replicate linear chromosomes.

What type of mRNA contains information for multiple genes?

Polycistronic mRNA Signup and view all the answers

What is the function of the Shine-Dalgarno sequence?

It assists in ribosomal binding during translation. Signup and view all the answers

Which type of mutation ends translation prematurely?

Nonsense mutation Signup and view all the answers

Which describes the difference between replication in eukaryotes and prokaryotes?

Eukaryotes have multiple origins of replication. Signup and view all the answers

What is a characteristic of monocistronic mRNA?

Is processed with splicing. Signup and view all the answers

Which type of mutation involves the addition of nucleotides, altering the reading frame?

Insertion Signup and view all the answers

In which cellular compartment does transcription occur in prokaryotes?

Cytoplasm Signup and view all the answers

Which type of DNA repair is responsible for correcting mismatched base pairs after DNA replication?

Mismatch repair Signup and view all the answers

What is a key distinguishing feature of horizontal gene transfer compared to vertical gene transfer?

Genes are transferred between cells of the same generation Signup and view all the answers

Which term describes the uptake of naked DNA from the environment?

Transformation Signup and view all the answers

What describes F+ cells in terms of gene transfer during conjugation?

They contain the F plasmid and can donate it Signup and view all the answers

What occurs during the lytic cycle of bacteriophage replication?

The phage causes the host cell to burst, releasing new viruses Signup and view all the answers

What defines specialized transduction in bacteriophages?

Specific bacterial genes near prophage integration sites are transferred Signup and view all the answers

What is the role of a repressor in an operon?

To inhibit transcription by binding to the operator Signup and view all the answers

Which mechanism of horizontal gene transfer requires direct contact between cells?

Conjugation Signup and view all the answers

What is the function of the promoter in an operon?

To initiate transcription by binding RNA polymerase Signup and view all the answers

What distinguishes Hfr cells in gene transfer?

They contain the F plasmid integrated into their chromosomes Signup and view all the answers

Study Notes

DNA's Essential Functions

DNA plays two crucial roles in cellular processes:
- Replication: Passing genetic information to offspring, ensuring continuity of traits.
- Gene Expression: Using genetic information to produce proteins, enabling cellular function.

Central Dogma of Molecular Biology

This fundamental principle describes the flow of genetic information:
- DNA is transcribed into RNA.
- RNA is translated into proteins.

Replication: Copying DNA

DNA unwinds, and new strands are synthesized using DNA polymerase, an enzyme that adds nucleotides to the growing strand.

Transcription: From DNA to RNA

RNA polymerase, an enzyme, transcribes DNA into messenger RNA (mRNA).

Translation: From RNA to Protein

Ribosomes read mRNA to assemble amino acids into proteins.

Eukaryotic vs Prokaryotic: Replication, Transcription, & Translation

Replication:
- Eukaryotes: Multiple origins of replication on linear chromosomes.
- Prokaryotes: Single origin of replication on circular chromosomes.
Transcription:
- Eukaryotes: Occurs in the nucleus; mRNA processing includes splicing (removing non-coding regions).
- Prokaryotes: Occurs in the cytoplasm; no mRNA splicing.
Translation:
- Eukaryotes: Occurs in the cytoplasm; uses monocistronic mRNA (one gene, one protein).
- Prokaryotes: Occurs in the cytoplasm; can use polycistronic mRNA (multiple genes, multiple proteins).

Monocistronic vs Polycistronic mRNA

Monocistronic mRNA (eukaryotes): Contains information for a single gene, resulting in one protein.
Polycistronic mRNA (prokaryotes): Contains information for more than one gene, allowing multiple proteins to be synthesized from a single mRNA molecule.

Shine-Dalgarno Sequence and Translation Initiation

The Shine-Dalgarno sequence is a ribosomal binding site in prokaryotic mRNA, located before the start codon. It helps facilitate translation initiation by guiding the ribosome to the correct starting point on the mRNA.

Mutations: Altering the Genetic Code

A mutation is a permanent change in the DNA sequence.
Types of mutations:
- Base-pair substitutions:
  - Silent: No change in the amino acid sequence, no effect on protein function.
  - Missense: A different amino acid is incorporated into the protein, potentially altering function.
  - Nonsense: A stop codon is introduced, prematurely ending translation, often leading to a non-functional protein.
- Deletion: Removal of nucleotides, shifting the reading frame, altering the amino acid sequence downstream.
- Insertion: Addition of nucleotides, shifting the reading frame, altering the amino acid sequence downstream.

Mutagens: Inducing Mutations

Chemical Mutagens: Chemicals that can alter DNA structure:
- Nitrous acid
- Alkylating agents
Physical Mutagens: Physical agents that can damage DNA:
- UV radiation
- X-rays

DNA Repair Mechanisms

Mismatch Repair: Corrects mismatched base pairs that arise during DNA replication.
Nucleotide Excision Repair: Removes and replaces damaged DNA segments.
Photoreactivation: Directly repairs UV-induced DNA damage using light.

Vertical vs Horizontal Gene Transfer

Vertical Gene Transfer: Passing genes from parent to offspring. This is the traditional mode of inheritance.
Horizontal Gene Transfer: Transfer of genes between cells in the same generation. This allows for rapid dissemination of genetic information, particularly in prokaryotes.

Mechanisms of Horizontal Gene Transfer

Transformation: The uptake of naked DNA from the environment by a competent bacterial cell.
Conjugation: Direct contact between cells, where one cell (F+) transfers DNA (plasmids) to another cell (F-).
Transduction: Mediated by bacteriophages (viruses that infect bacteria), where bacterial DNA is packaged into a phage and transferred to another host cell.

F+, F-, F', and Hfr Cells

F+ Cells: Contain the F plasmid, which allows them to act as donors during conjugation.
F- Cells: Lack the F plasmid and act as recipients during conjugation.
F' Cells: Have the F plasmid integrated into the chromosome, carrying chromosomal DNA along with it during conjugation.
Hfr Cells: High-frequency recombination cells, where the F plasmid is integrated into the chromosome. These cells efficiently transfer chromosomal DNA during conjugation.

Bacteriophage Replication Cycles

Lytic Cycle: The phage replicates rapidly, causing the host cell to burst (lyse) and release new phages.
Lysogenic Cycle: The phage DNA integrates into the host genome, becoming a prophage. The phage replicates along with the host genome without killing the cell immediately.

Generalized vs Specialized Transduction

Generalized Transduction: Any part of the bacterial chromosome can be packaged into a phage and transferred to a new host cell.
Specialized Transduction: Only specific bacterial genes adjacent to the prophage integration site are transferred to a new host cell.

Operons: Gene Regulation in Prokaryotes

Operon: A group of genes that are regulated together, often involved in a specific metabolic pathway.
Operator: The DNA sequence where repressors bind to inhibit transcription.
Promoter: The DNA sequence where RNA polymerase binds to initiate transcription.
Regulatory Gene: Produces proteins that control the operon.
Repressor: A protein that binds to the operator to inhibit transcription.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Explore the essential functions of DNA, including replication and gene expression. This quiz also covers the central dogma of molecular biology, detailing how genetic information flows from DNA to RNA to proteins. Understand the differences between eukaryotic and prokaryotic processes.