Genetics and Molecular Biology Quiz

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Questions and Answers

What is the primary purpose of genetic recombination?

To exchange segments between DNA molecules (correct)

To amplify DNA sequences

To transfer genes between generations

To replicate DNA without mutations

Which process is characterized by the transfer of genetic material within the same generation?

Vertical gene transfer

Mutation accumulation

Horizontal gene transfer (correct)

Clonal propagation

What are recombinants?

Cells that are unable to evolve

Cells that transfer genes vertically only

Cells that contain new nucleotide sequences (correct)

Cells that replicate their genomes without change

What is one area where PCR is commonly applied?

Forensic science Signup and view all the answers

Which of the following is NOT a step in the polymerase chain reaction (PCR)?

Replication Signup and view all the answers

What is one characteristic of plasmids?

They replicate independently of chromosomal DNA. Signup and view all the answers

Which type of factor is specifically related to antibiotic resistance?

R factor Signup and view all the answers

What does the F factor in plasmids signify?

A fertility factor associated with conjugation. Signup and view all the answers

What is one function of a virulence factor?

To encode traits for disease causation. Signup and view all the answers

What is true about the proofreading functions in cellular organisms?

They help to correct errors when DNA is replicated. Signup and view all the answers

Which feature differentiates prokaryotic cells from eukaryotic cells?

Presence of membrane-bound organelles Signup and view all the answers

What is the primary structural component of a bacterial cell wall?

Peptidoglycan Signup and view all the answers

Which type of bacteria is typically more susceptible to penicillin?

Gram-positive Signup and view all the answers

What role does the capsule of a bacterium play?

Immune evasion Signup and view all the answers

What is the primary purpose of pili in bacteria?

DNA transfer Signup and view all the answers

Which bacterial structure is useful for forming biofilms?

Fimbriae Signup and view all the answers

Which of the following bacteria can resist being stained by an acid-fast stain?

Staphylococcus Signup and view all the answers

What is a significant feature of Gram-negative bacteria regarding their cell wall?

Presence of endotoxins Signup and view all the answers

What is the approximate size range of prokaryotic cells?

0.1-5 mm Signup and view all the answers

Which type of ribosomes are found in prokaryotic cells?

70S Signup and view all the answers

What function do inclusions serve in prokaryotic cells?

Resource storage Signup and view all the answers

What is a characteristic of the slime layer surrounding some bacteria?

Sticky, less organized layer Signup and view all the answers

What is the purpose of measuring microbial growth?

For diagnostic purposes Signup and view all the answers

What characteristics distinguish endospores from vegetative cells?

Endospores are dehydrated and dormant. Signup and view all the answers

Which metabolic process requires oxygen as a final electron acceptor?

Aerobic respiration Signup and view all the answers

What is a significant reason for bacteria to undergo fermentation instead of complete glucose oxidation?

Lack of oxygen Signup and view all the answers

Which of the following describes the end products of the acetone-butanol fermentation pathway?

Acetone, butanol, and ethanol Signup and view all the answers

What is the primary characteristic of the growth phase referred to as 'exponential growth' in microbial populations?

Rapid increase in cell number Signup and view all the answers

What role do macronutrients play in microbial growth?

They provide essential carbon for energy. Signup and view all the answers

What is the optimum pH level for most bacterial growth associated with pathogens?

Neutral pH around 7 Signup and view all the answers

Which type of phosphorylation occurs primarily during fermentation?

Substrate-level phosphorylation Signup and view all the answers

Which group of bacteria is known for producing endospores?

Certain genera of Bacillus and Clostridium Signup and view all the answers

In which scenario would a bacterium most likely utilize aerobic respiration?

In an oxygen-rich environment with sufficient nutrients Signup and view all the answers

Which statement correctly describes the role of enzymes in microbial metabolism?

Certain substrates are catabolized by specific bacterial species. Signup and view all the answers

How does microbial metabolism contribute to the identification of bacteria in clinical settings?

Unique metabolic capabilities create easily distinguishable growth patterns. Signup and view all the answers

What is the primary function of metabolism in bacteria?

For growth and reproduction Signup and view all the answers

Study Notes

Course Information

Course title: CSF-6250 Integrative Pathophysiology & Biomechanics in Health Care 2
Module: Microbes in Human Health and Disease
Unit: 03 - Bacteria

Unit 3 Objectives

Differentiate prokaryotic and eukaryotic cells
Recognize structural and functional features of bacterial species useful for diagnostic purposes
Recognize methods for measuring microbial growth
List factors affecting microbial growth
Name the three processes of horizontal gene transfer in bacteria
Recognize the purpose and applications of PCR and CRISPR

Lesson 1: Prokaryotic Cells

Salmonella typhimurium invades cultured cells

The Prokaryotic Cell

Prokaryotes are small and simple (0.1-5 mm)
They are unicellular
They lack a nucleus
They have circular DNA
They lack membrane-bound organelles
Components of a prokaryotic cell include: plasma membrane, cell wall, capsule, pilus, flagellum, cytoplasm, ribosome, nucleoid, inclusion, and plasmid.

Prokaryotic and Eukaryotic Cells

Prokaryotes: small, simple cells (0.1-5 mm)
Unicellular
Lack a nucleus, circular DNA, and membrane-bound organelles.
Eukaryotes: large, complex cells (10-100 mm)
Uni- or multicellular
Possess a nucleus, linear DNA, and membrane-bound organelles.

Bacterial Cell Shapes and Arrangements

Bacterial shapes are species-specific and useful in diagnosing infections.
Common shapes include coccus (round), bacillus (rod), vibrio (curved rod), coccobacillus (short rod), spirillum (spiral), and spirochete (long, loose, helical spiral). Common arrangements include single coccus, diplococcus, tetrad, streptococcus, staphylococcus, and chain of rods.

CM and Cytoplasm of Prokaryotic Cells

Cell membrane (CM): lipid bilayer, without cholesterol, high protein content
Ribosomes: 70S (vs 80S in eukaryotic cells); target for certain antibiotics
Inclusions: storage of resources in polymerized form (e.g., volutin in Corynebacterium diphtheriae)

External Structures of Prokaryotic Cells: Cell Wall

Major component: peptidoglycan
Protects from osmotic pressure
Several types of antibiotics inhibit peptidoglycan synthesis (e.g., penicillin)

External Structures of Prokaryotic Cells: Gram-positive and Gram-negative Cell Wall

Gram-positive: thicker peptidoglycan layer, lacks outer membrane, and contains teichoic acid.
Gram-negative: thinner peptidoglycan layer, has an outer membrane, and contains lipopolysaccharide (LPS).
LPS is an endotoxin.

External Structures of Prokaryotic Cells: Gram-positive and Gram-negative Stain

Gram staining differentiates between Gram-positive and Gram-negative bacteria.
Gram-positive bacteria stain purple; Gram-negative bacteria stain pink.

External Structures of Prokaryotic Cells: Clinical Significance of Cell Wall Type

Gram-positive: high susceptibility to penicillin and lysozyme, low sensitivity to heat and disinfectants, and lack of endotoxin.
Gram-negative: low susceptibility to penicillin and lysozyme, high sensitivity to heat and disinfectants, and presence of endotoxin.
Various species produce exotoxins.

External Structures of Prokaryotic Cells: Acid Fast Cell Wall

Gram-positive bacteria with a waxy mycolic acid layer
Stained pink using acid-fast stain
Clinically important acid-fast bacteria include Mycobacterium tuberculosis and Mycobacterium leprae

External Structures of Prokaryotic Cells: Capsule

Found in some species; outside the cell wall
Cannot be stained; visualized by negative staining
Glycocalyx (sugar coat) consists of polysaccharides or proteins
Functions: water retention and biofilm formation

External Structures of Prokaryotic Cells: Flagella, Fimbriae

Flagella: motility structures; presence and arrangement are species-specific
Fimbriae: sticky appendages, often numerous, contribute to biofilm formation

External Structures of Prokaryotic Cells: Pilus/Pili

Hollow tubes (made of protein)
Longer than fimbriae, shorter than flagella
Function: DNA transfer between bacterial cells (conjugation)

Endospores

Found in some gram-positive genera of bacteria (Bacillus and Clostridium)
Dormant stage under unfavorable conditions
Resist sterilization
Species-specific morphology (e.g. terminal, central, or lateral)

Commonly Used Stains

Different stains used to visualize different bacterial components (e.g., Gram stain, acid-fast stain, endospore stain, flagella stain, capsule stain)

Lesson 2: Bacterial Metabolism

Comprehensive overview of bacterial metabolic processes, including central pathways, respiration, and fermentation.

Metabolism

Metabolism = catabolism + anabolism
Ultimate function: growth and reproduction
Catabolism: breaking down large molecules to release energy
Anabolism: using energy to assemble small molecules into larger ones

Carbohydrate Catabolism

Aerobic respiration (with oxygen)
Anaerobic respiration (without oxygen)
Fermentation (no electron transport chain)

Fermentation

Incomplete oxidation of glucose (or other nutrients) in the absence of oxygen
Produces organic acids, alcohol, and/or gases (e.g., lactic acid, ethanol).

Carbohydrate Catabolism: Aerobic vs Anaerobic

Aerobic respiration requires oxygen, produces more ATP, and completely oxidizes glucose
Fermentation does not require oxygen, produces less ATP, and incompletely oxidizes glucose

Fermentation Products

Various products resultant from various types of fermentations.
Different microbes create various commercial products.

Use of Microbial Metabolism in Medicine

Identifying bacteria using metabolic tests that are quick, inexpensive, and simple.
Different metabolic products help identify bacterial species/strains.

Lesson 3: Bacterial Growth and Nutrition

Define and explain microbial growth (increase in cell number, not cell size)
Growth rates vary with type of microbe
Optimal conditions for growth in a species vary.

Microbial Growth

Rapid, exponential growth under optimal conditions
Generations (time to double) vary
Factors affecting growth include:
Chemicals: macro/micronutrients, oxygen, water
Physical: temperature, pH, osmolarity

Microbial Growth and Nutrition: Chemical Requirements

Key nutrients for bacterial growth include nitrogen (needed in higher concentrations than in humans; peptidoglycan in cell wall).
Oxygen utilization varies
Obligate/facultative aerobes.

Microbial Growth and Nutrition: Chemical Requirements (Cont'd)

Macronutrients: needed in large quantities, provide carbon, energy, protein, and elements.
Micronutrients: needed in smaller quantities, some are coenzymes in metabolic reactions.
Growth factors: vitamins, vitamin-like molecules.

Microbial Growth and Nutrition: Physical Factors – Osmotic Pressure

High osmotic pressure (high salt or sugar environment) pulls water out of cells, inhibiting bacterial growth.
Water is a critical solvent for cellular functions.

Microbial Growth and Nutrition: Microbial Growth Curve

Stages of bacterial growth include lag phase, log phase, stationary phase, and death phase.

Microbial Growth and Nutrition: Measuring Microbial Growth - Direct

Direct microscopic cell counts and viable plate counts using serial dilutions, and membrane filtration.

Microbial Growth and Nutrition: Measuring Microbial Growth - Indirect

Indirect methods like turbidity with a spectrophotometer measure microbial growth based on cloudiness.

Lesson 4: Bacterial Genetics

Describe prokaryotic vs eukaryotic genomes
Explain plasmids, which are small, extrachromosomal circular DNA molecules.

Prokaryotic versus Eukaryotic Genomes

Prokaryotes have one circular chromosome in cytoplasm. Plasmids are present in some cells.
Eukaryotes have multiple linear chromosomes in the nucleus and in cytoplasm.

What are Plasmids?

Small circular DNA molecules that replicate independently of chromosomal DNA
Contain genes that confer advantages, such a resistance to antibiotics or heavy metals. Other examples include fertility or virulence factors

The Central Dogma of Molecular Biology

DNA replication, transcription (conversion to RNA), translation (conversion to proteins)
Processes are similar in prokaryotes and eukaryotes

Genetic Recombination and Transfer

Genetic recombination exchanges segments of DNA between molecules
Recombinants are cells possessing new nucleotide sequences, which results from vertical or horizontal transfer.
Vertical gene transfer is from one generation to another.
Horizontal gene transfer is within generations, which contributes to genetic diversity.

Horizontal Gene Transfer in Prokaryotes

Transformation: uptake of free DNA
Transduction: transfer via bacteriophage
Conjugation: direct transfer via a pilus

Gene Technology: PCR

Polymerase chain reaction (PCR) amplifies DNA (or RNA)
Areas of application include diagnostics, forensics, and biomedicine

Gene Technology: CRISPR

Clustered, Regularly Interspaced Short Palindromic Repeats (CRISPR)
CRISPR-associated proteins (Cas) are used to edit genomes
Applications include medicine, biotechnology, agriculture, and epidemiology

Summary

Course content summarizes differences between prokaryotic and eukaryotic cells; bacterial metabolism, growth, and genetics; and principles for two important gene technologies.

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Description

Test your knowledge on genetic recombination, polymerase chain reaction (PCR), and plasmids. This quiz covers key concepts in genetics, techniques used in molecular biology, and the significance of various factors in microorganisms. Challenge yourself and enhance your understanding of these fundamental topics.