MICR 3050- Majors Final Exam Unit 4

What is a virus?

Genetic elements that replicate independently of a cell's chromosome but requires a living host in order to replicate

What makes up a virion?

Nucleic acid surrounded by a protein coat

2 types of symmetry for viruses

Helical Icosahedral

Symmetry for a Bacteriophage

Binal

Positive Sense ssRNA Virus

Genome and mRNA are the same

Negative Sense ssRNA Virus

Genome and mRNA and complentary

6 basic steps to viral replication

1. Attachment 2. Entry 3. Uncoating of the Genome 4. Synthesis 5. Assembly 6. Release

Characteristics of the Lytic Cycle

Mulitplication begins immediately after entering the host Bacterial cell lyses to release bacteriophages Ex: T4

Characteristics of the Lysogenic Cycle

Can reproduce as virulent phages OR can remain in cell without destruction Ex: Lambda

What is the process that converts the lysogenic cycle to the lytic cycle?

Induction

Lysogeny

Nonlytic relationship between a phagee and the host

Where does a prophage always integrate?

Between the galactose and biotin operons

What is the process called when a prophage could change the phenotype of its host?

Lysogenic Conversion

What triggers induction of the lytic cycle?

A drop in the lambda repressor levels

Are animal viruses naked or enveloped?

Enveloped

Virulent Viruses

Follows the lytic cycle Virions are made and the cell lyses

Cancer Viruses

Virus incorporates and mutates the chromosome Series of events must take place in order for the cancer to appear

Latent Viral Infections

Virus stops producing and remains dormant Symptoms/antibodies/virus is no detectable Ex: Herpes Simplex, Varicella

Persistent Viral Infection

Virus is detectable Clinical symptoms can be mild or absent for periods of time Ex: Hepatitis B, HIV

Retrovirus

RNA virus that replicates through a DNA intermediate Enveloped Use reverse transcriptase

Nucleoid

Location of chromosom and associated proteins in bacteria

Plasmids

Extra chromosomal DNA Usually small, closed, circular DNA Contain non-essential genes Exist and replicate independently

Screening

Detecting mutants via observation

Selectable Mutations

Confer some type of advantage to the organisms that possess them

Selection

Placing organisms under conditions where the growth of those with a particular genotype will be favored

Homologous Recombination Steps

1. DNA is nicked 2. SSB and Rec A protein complex formed 3. Recipient DNA invaded 4. Crossover

Transformation

Uptake of naked DNA by a competent cell followed by the incorporation of DNA in the recipient cell's genome

Generalized Transduction

1. Normal lytic cycle 2. Transducing particle with donor DNA and normal phages produced 3. Transducing particle attaches to host cell and injects DNA 4. Homologous recombination

Specialized Transduction

*Carried out by temperate phages and occurs when prophage is excised incorrectly 1. Induction into lytic phase 2. Phage DNA become circular and detaches from host genome 3. Detached DNA replicates 4. Cell lyses

Bacterial Conjugation

Use of a sex pilus between 2 cells to transfer one strand of F+ cell to F- cell where synthesis of a complentary strand takes place

PCR

Synthesizes large quantities of a DNA fragment

What are the 4 things required for PCR?

Target DNA Primers Thermostable DNA polymerase Deoxyribonucleotide triphosphates

3 repeated steps of PCR

Denaturing Annealing Extension

3 main steps of molecular cloning

Isolation/Fragmentation of source DNA Insertion of DNA into cloning vector Introduction of cloned DNA into host

What type of ends are better when it comes to restriction endonucleases?

Single Strand Sticky Ends

6 Benefits to using plasmids as cloning vectors

Small Size Easy to Purify Independent ORI Multiple Copy Number Presence of selectable markers Unique Cloning sites

Microflora

Microbes regularly found at an anatomical site Associated with healthy body-tissue

When does the microflora relationship begin?

At birth

3 microenvironments of the skin

Dry Moist Sebaceous

Characteristics of bacteria of the skin

Low water activity Acid-tolerant Salt-tolerant

Example of commonly found bacteria of the skin

Propionibacterium acnes

Characteristics of the Mouth

Moist Nutrient Rich Neutral pH Ambient Temp

Example of commonly found bacteria of the mouth

Streptococcus spp.

Characteristics of the Stomach

pH of 2 <10 bacteria/mL per person

Bacteria commonly found to survive in the stomach

Heliocobacter pylori

Characteristics of the small intestine

Increasing pH and the number of bacteria as you progress through the small intestines

Bacteria commonly found in the small intestine

Enterococcus faecalis Lactobacilli

Characteristics of the colon

Largest microbial population of the body Most microbes are obligate anaerobes

Bacteria found most commonly in the colon

Bacteroides Clostridium

Bacteria make up what amount of weight of fecal matter?

1/3

Bacteria commonly found in the upper respiratory tract

Staphylococci Streptococci

3 benefits of the relationship between the microbiota and host

Colonization Resistance Development of the immune system Produces vitamins, amino acids, and organic acids

Infection

Microbes in the host that do not harm the host's tissue

Disease

Microbes that develop toxicity or invasiveness and contrinutes to the damage of host tissues

Innate Immunity

1st line of defense Body's ability to recognize and destroy pathogens or their products Lacks memory

Adaptive Immunity

2nd line of defense Body's ability to recognize pathogens based on their antigens Has memory Has the ability to self-recognize