Introduction

Question 1

Parasitism

Answer 1

A relationship in which a host provides the primary benefit to the parasite.

Question 2

Mutualism

Answer 2

One that benefits all of the contributing parties.

Eg: Lichens consisting of fungus and algae or cyanobacterium.

Question 3

Most heterogeneous subset of all living creatures

Answer 3

Microorganism

Question 4

Prokaryotes

Answer 4

Without true nucleus,
Circular chromosomes with d.s. DNA w/o histones,
Single gene, only axons are present,
Nucleoli absent,
Ribosomes 70s subunit,
No organelles present,
Ribosomes present,
mRNA polycistronic with multiple shine dalagarno sequences.
Cell-cell communication mechanism aka quorum sensing (depends on production of auto inducers or pheromones that enables the bacterium to monitor its own cell population density) to regulate the transcription of genes in diverse physiological processes.
Are haploid.

Question 5

Eukaryotic microorganism

Answer 5

Algae, Protozoa, fungi, and slime molds.

Question 6

Plasmids

Answer 6

Extra chromosomal d.s. DNA in bacteria that are capable of replication within at least one cell line,
Can alter the virulence,
Exhibit a broad host range that allows them to convey sets of genes to diverse organisms:
Capability to adhere via adhesins,
Produce resistance to certain drugs.

Question 7

Bacteriophages

Answer 7

Viruses capable of injecting genetic material, eg diphtherium bacterium.

Question 8

Jumping genes/ transposons

Answer 8

Special type of d.s. DNA fragments which jump around,

Can alter the pathogenicity of bacteria.

Question 9

Viroids

Answer 9

Naked (extra cellular form) infectious RNA molecules (small, single stranded existing as highly base paired rodlike structures, contains no protein encoding genes), produce infection in plants,
Size 246 to 375 nucleotides in length,
Totally dependent on host functions for replication,
Replicated by the DNA dependent RNA polymerase of the plant host,
Contains inverted repeated base sequences at their 3’ and 5’ ends.

Question 10

Virus

Answer 10

Non-living/ non-cellular infectious agents,

Has either DNA or RNA with protein cover.

Question 10

Virophages

Answer 10

Viruses that infect other viruses.

Question 12

Virus- protein coat/ capsid

Answer 12

Glycoproteins,
Determine the specificity of interaction of a virus with its host cell,
Protects the nucleic acid and facilitate attachment and penetration of the host cell by the virus.

Question 13

Viral replication

Answer 13

Inside the cell, viral nucleic acid redirects the host’s enzymatic machinery to functions associated with replication of the virus. Or the genetic information from the virus can be incorporated as DNA into a host chromosome. Or the viral genetic information can serve as a basis for cellular manufacture and release of copies of the virus. This process calls for replication of the viral nucleic acid and production of specific viral proteins.
Maturation consists of assembling newly synthesised nucleic acid and protein subunits into mature viral particles, which are then liberated into the extra cellular environment.

Question 14

Small virus replication

Answer 14

Similar but requires the assistance of another virus in the host cell for their duplication. The delta agent, aka hepatitis D virus is too small to code for even a single capsid protein and needs help from hepatitis B virus for transmission.

Question 15

Smallest infectious particle

Answer 15

Prions

Question 15

Scrapie

Answer 15

Degenerative CNS disease of sheep.

Question 16

Prions

Answer 16

Cellular form of the prion proteins PrPc is encoded by the hosts chromosomal DNA. PrPc- sialoglycoprotein, molecular mass 33000-35000 daltons, high content of alpha helical secondary structure i.e. sensitive to proteases and soluble in detergent, PrPc expressed on the surface of neurons via glycosylphosphatidyl inositol anchor in both infected and uninfected brains. Conformational change occurs in the prion proteins, changing it from its normal or cellular form PrPc to the disease causing conformation PrPSc implying when present in an individual, it is capable of recruiting PrPSc and converting it to disease form.
Eg: Kuru, CJD, Gerstmann-Straussler-Scheinker dz, fatal familial insomnia, BSE/ mad cow dz, vCJD.
Capable of causing chronic neurologic diseases.

Question 17

Acquired human prion dz

Answer 17

vCJD associated with ingestion of prion infected particles, kuru, CJD.

Question 18

Sporadic human prion dz

Answer 18

CJD unknown source.

Question 19

Familial human prion dz

Answer 19

Great an-straussler-scheinker dz, fatal familial insomnia, CJD associated with specific mutations within the gene coding PrP.

Question 21

beta pleated arrangements of protein include

Answer 21

Prion proteins, silk, amyloid.

Question 22

Smallest infectious living organisms.

Answer 22

Mycoplasma: Parasitic prokaryotes, no cell wall, adaptation has resulted in incorporation of sterol into their cell membranes.

Question 23

Microbial eukaryotes

Answer 23

Protists: are members of the following four major groups i.e. algae, Protozoa, fungi, slime molds.

Question 24

Algae

Answer 24

Denote all organisms that produces O2 as a product of photosynthesis,
Contains chlorophyll,
Are unicellular or multicellular,
Can produce toxins that are poisonous to humans and animals.
Eg: Kelps- brown algae, several hundred meters in length;
Dinoflagellates- unicellular alga, cause algal blooms or red tides, mainly Gonyaulax species can produce neurotoxins such as SAXITOXINS or GONYAUTOXINS, which accumulate in shellfish and ingestion of these shellfish by humans results in symptoms of PARALYTIC SHELLFISH POISONING that can lead to death.

Question 25

Dinoflagellate Gonyaulax species

Answer 25

Dinoflagellates- unicellular alga, cause algal blooms or red tides, mainly Gonyaulax species can produce neurotoxins such as SAXITOXINS or GONYAUTOXINS, which accumulate in shellfish and ingestion of these shellfish by humans results in symptoms of PARALYTIC SHELLFISH POISONING that can lead to death.

Question 26

Protozoa

Answer 26

Unicellular non photosynthetic protists, heterotrophs.

Sporozoa- strict parasites, immobile, reproduce sexually and asexually in alternate generations by means of spores.

Question 27

Fungi

Answer 27

Non photosynthetic protists growing as a mass of branching, interlacing filaments aka hyphae known as MYCELIUM, are coenocyte confined within a branching tubes, cell wall is chitin.
Yeasts do not form mycelium.
Subdivisions: chytridiomycota, zygomycota (zygomycetes), ascomycota (ascomyctes), basidiomycota (basidiomycetes), deutromyocetes ( imperfect fungi).

Question 28

Slime molds

Answer 28

Characterised by the presence, as a stage in their life cycle, of an amoeboid multinucleate mass of cytoplasm called plasmodium- coenocytic, cytoplasmic flow is confined to the branching network of chitinous tubes, causes plasmodium to migrate in the direction of its food source, in response to a chemical signal, 3’,5’-cyclic AMP, plasmodium which reaches macroscopic size, differentiates into a stalked body that produces individual motile cells, which are flagellated or ameboid, initiate a new round in the life cycle of slime molds.

Question 29

Infectious agent that simultaneously contains both DNA and RNA

Answer 29

Bacteria