Biol 221 Exam 2 Study Guide

These flashcards cover key concepts in biology related to DNA structure, replication, transcription, translation, microbial control, and bacterial growth.

What does antiparallel mean in DNA structure?

Refers to the two strands of DNA running in opposite directions.

What are the three parts of a nucleotide?

A phosphate group, a sugar (deoxyribose in DNA), and a nitrogenous base.

Explain proper base pairing of nucleotides in DNA.

Adenine pairs with Thymine (A-T) and Guanine pairs with Cytosine (G-C).

Define genome.

The complete set of genes or genetic material present in a cell or organism.

What is the overall process of DNA replication?

The process by which DNA makes a copy of itself, resulting in two identical DNA molecules.

What is the site where DNA replication begins on a bacterial chromosome called?

The origin of replication.

Which enzyme synthesizes the new DNA strand during DNA replication?

DNA polymerase.

In what direction does DNA polymerase read the template DNA?

DNA polymerase reads the template DNA in the 3' to 5' direction.

In what direction is new DNA assembled?

New DNA is assembled in the 5' to 3' direction.

Describe the synthesis of the lagging strand of DNA.

The lagging strand is synthesized in short segments called Okazaki fragments.

What is an Okazaki fragment?

Short sequences of DNA synthesized on the lagging strand during DNA replication.

What is the function of DNA ligase?

Joins together Okazaki fragments on the lagging strand.

What does helicase do?

Unwinds the DNA double helix ahead of the replication machinery.

What is the Central Dogma of molecular biology?

It describes the flow of genetic information from DNA to RNA to protein.

Define transcription.

The process of synthesizing RNA from a DNA template.

Define translation.

The process of creating a protein from an mRNA sequence.

Which enzyme synthesizes the RNA strand during transcription?

RNA polymerase.

What are the three types of RNA?

mRNA (messenger RNA), tRNA (transfer RNA), and rRNA (ribosomal RNA).

In which direction does RNA polymerase read the DNA?

RNA polymerase reads DNA in the 3' to 5' direction.

In which direction does RNA polymerase synthesize mRNA?

RNA polymerase synthesizes mRNA in the 5' to 3' direction.

What nucleotide base is present in DNA but not in RNA?

Thymine (T); RNA uses Uracil (U) instead.

When given a DNA sequence, how can you derive the RNA sequence?

By replacing Thymine (T) with Uracil (U) and transcribing the complementary bases.

Where does transcription start and stop on DNA?

Transcription starts at the promoter region and stops at the terminator region.

What are the basic steps of translation?

Initiation, elongation, and termination.

Where does translation start and stop on mRNA?

Translation starts at the AUG start codon and stops at stop codons (UAA, UAG, UGA).

Define codon.

A sequence of three nucleotides on mRNA that corresponds to a particular amino acid.

Define anticodon.

A sequence of three nucleotides on tRNA that is complementary to a codon in mRNA.

What is the genetic code?

The set of rules by which information encoded in genetic material is translated into proteins.

Where do transcription and translation occur in prokaryotes?

Both occur in the cytoplasm.

Where do transcription and translation occur in eukaryotes?

Transcription occurs in the nucleus, translation occurs in the cytoplasm.

Define exons and introns.

Exons are coding sequences in RNA that are expressed; introns are non-coding sequences that are removed.

Why is it advantageous for bacteria to regulate gene expression with operons?

It allows for coordinated control of genes involved in similar functions, thereby conserving resources.

List and describe the parts of an operon.

Regulator, promotor, operator, and structural genes.

Give an example of an inducer.

Lactose can act as an inducer in the lac operon.

Give an example of a repressor.

The LacI protein is a repressor that inhibits expression of the lac operon.

What is a missense mutation?

A mutation that results in a different amino acid being incorporated into the protein.

What is a nonsense mutation?

A mutation that introduces a premature stop codon, leading to truncated proteins.

What is a silent mutation?

A mutation that does not change the amino acid sequence of a protein.

What is a frameshift mutation?

A mutation that shifts the reading frame by inserting or deleting nucleotides.

What are generalized causes of DNA mutations?

Spontaneous errors during DNA replication, exposure to mutagens, and radiation.

What is transduction?

The process of transferring DNA from one bacterium to another via a bacteriophage.

What is transformation?

The uptake of free DNA from the environment by a bacterial cell.

What is conjugation?

The transfer of DNA between bacteria through direct contact.

What are plasmids?

Small, circular DNA molecules that are separate from chromosomal DNA and can replicate independently.

What is binary fission?

The process by which a bacterial cell divides into two identical daughter cells.

How do you calculate the number of bacteria after a number of generations?

Using the formula N = N0 * 2^n, where N0 is the initial number of bacteria and n is the number of generations.

What are the phases of the bacterial growth curve?

Lag, exponential (log), stationary, and death phases.

What are the five groups of bacteria in terms of temperature range?

Psychrophiles, psychrotrophs, mesophiles, thermophiles, and hyperthermophiles.

What is the optimal temperature for psychrophiles?

Around 15°C.

What is the optimal temperature for mesophiles?

Around 37°C (human body temperature).

Where can you find examples of psychrophiles?

In cold environments like Arctic and Antarctic regions.

What is the preferred pH range for most bacteria?

Neutral to slightly acidic, around 6.5 to 7.5.

Define acidophile.

An organism that thrives in acidic environments.

What is a halophile?

An organism that thrives in highly saline environments.

What is the difference between an obligate halophile and a facultative halophile?

Obligate halophiles require high salt concentrations, while facultative halophiles can tolerate salt but do not require it.

What is osmosis?

The diffusion of water across a semipermeable membrane.

How does a hypertonic environment affect a bacterial cell?

Causes plasmolysis or shrinkage due to water loss.

How does a hypotonic environment affect a bacterial cell?

Causes the cell to swell and potentially burst due to water influx.

Why is oxygen required by some bacteria?

For cellular respiration to produce ATP.

Why is oxygen toxic to other bacteria?

Due to the production of reactive oxygen species (ROS) that can damage cellular components.

What are the categories of oxygen requirements by bacteria?

Obligate aerobes, facultative anaerobes, obligate anaerobes, aerotolerant anaerobes, and microaerophiles.

Define capnophile.

An organism that thrives in environments with high carbon dioxide concentrations.

What are the main chemical requirements of a bacterial cell?

Macronutrients (C, N, O, H, P, S) and micronutrients (such as trace elements).

How does a bacterial cell utilize chemicals?

For growth, metabolic processes, and energy production.

Define autotroph.

An organism that produces its own food from inorganic compounds.

Define heterotroph.

An organism that obtains its food from organic compounds.

What are the types of symbiotic relationships?

Mutualism, commensalism, and parasitism.

Define sterilization.

The complete elimination of all microbes, including spores.

Define sanitization.

Reduction of microbial populations to safe levels.

Define contamination.

The presence of unwanted microorganisms.

Define decontamination.

The process of removing contaminants.

Define sepsis.

The presence of toxic substances or infection in the blood.

Define antiseptic.

A substance that inhibits microbial growth on living tissues.

Define disinfectant.

A substance that kills or inhibits microorganisms on inanimate objects.

Define degerming.

The removal of microorganisms from the skin or surfaces.

Define bacteriostatic.

A substance that inhibits the growth of bacteria without killing them.

Describe the process of proper handwashing.

Washing hands with soap and water for at least 20 seconds to remove dirt and microbes.

Compare the effectiveness of moist heat, dry heat, and refrigeration in microbial control.

Moist heat is most effective for sterilization; dry heat is less effective; refrigeration slows microbial growth.

Which microbial control methods work quickly to kill microbes?

Boiling, autoclaving, and some chemical disinfectants.

Which methods achieve sterilization?

Autoclaving, dry heat sterilization, and radiation.

What microbial structure is damaged by radiation?

DNA.

What are some practical examples of how radiation is used for microbial control?

UV light for sterilizing surfaces, gamma rays for sterilizing food and medical supplies.

What is filtration?

A method to remove microbes from liquids or air by using a filter.

How is filtration used for microbial control?

To sterilize heat-sensitive liquids like vaccines and culture media.

What factors affect how well chemical antimicrobials kill microbes?

Concentration, contact time, temperature, and microbial resistance.

What is the difference between residue-producing and non-residue-producing chemicals?

Residue-producing chemicals leave a residual antimicrobial effect, while non-residue-producing chemicals do not.

What is a negative effect of the overuse of antimicrobial chemicals?

Development of resistant microbial strains.

What are the limits of microbial control?

Not all microbes can be eliminated; some may survive under treatment.

What are surfactants?

Surface-active agents that reduce the surface tension of liquids and help in cleaning.

What are quats?

Quaternary ammonium compounds used as disinfectants.

What are phenols?

Chemical compounds used as disinfectants and antiseptics.

What are heavy metals?

Metals like mercury, silver, and copper used in some antimicrobial applications.

What is the ideal concentration of alcohol for killing microbes?

70% ethanol or isopropyl alcohol.

In what situations should alcohol-based hand sanitizers not replace handwashing?

When hands are visibly dirty or greasy.

Why is adding residue-producing triclosan to cleaning products a bad practice?

It can contribute to antimicrobial resistance and disrupt microbial ecosystems.

What microbial controls can inactivate endospores?

Autoclaving and certain chemical sterilants.