MICR 271 Exam Questions with Correct Answers Latest Update 2025-2026
Three domains of life - Answers Bacteria, Archaea, Eukaryota
If a eukaryote has a membrane-enclosed nucleus, a prokaryote has: - Answers a nucleoid, not
membrane enclosed
If a eukaryote has lysosomes/peroxisomes, a prokaryote has: - Answers not present
If a eukaryote has an endoplasmic reticulum/golgi apparatus, a prokaryote has: - Answers not
present
If a eukaryote has a mitochondria, a prokaryote has: - Answers not present
Bacteria - Answers Domain of unicellular prokaryotes that have cell walls containing
peptidoglycan
Archaea - Answers Domain of unicellular prokaryotes that have cell walls that do not contain
peptidoglycan
Eukaryota - Answers Domain of organisms that contain a nucleus and other membrane
enclosed organelles
endosymbiont hypothesis - Answers eukaryotes evolved from prokaryotes, based on the
similarities found between bacteria and mitochondria
Symbiosis - Answers the living together to close association of two dissimilar organisms, each
being known as a symbiont
Differences between mitchondria+chloroplast and other organelles - Answers contain their own
DNA and have a distinct translation system
a-proteobacteria - Answers a subgroup of proteobacteria, which are a large group of eubacteria,
primarily Gram-negative, that 16S rRNA sequence comparisons show to be phylogenetically
related
Archezoan Scenario - Answers A primitive amitochondrial eukaryote cell phagocytosed as an a-
protobacterium - leading to the evolution of the mitochondrion
symbiogenesis scenario - Answers A single endosymbiotic event involving the uptake of an a-
protobacterium by an archaeal cell led to the generation of the mitochondria, followed by the
evolution of the nucleus and compartmentalization of the eukaryotic cell
Phylogeny - Answers the evolutionary history of a group of organisms
Phylogenetic tree of life - Answers compares the rRNA sequences between organisms
Comparing the domains of life: nucleus - Answers bacteria: no
,archaea: no
eukaryota: yes
Comparing the domains of life: RNA polymerase - Answers bacteria: 3-4 subunits
archaea: 8-12 subunits
eukaryota: 12-14 subunits
Comparing the domains of life: Ribosomes - Answers bacteria: 70S
archaea: 70S
eukaryota: 80S
Comparing the domains of life: cell wall - Answers bacteria: murein (peptidoglycan)
archaea: no murein
euakryota: no murein
Phylogenomic tree of life - Answers Tree of life based on complete genomes of organisms
horizontal gene transfer - Answers the movement of genetic material between organisms other
than via vertical transmission (parent to child)
Obligate intracellular parasite - Answers A parasite that cannot reproduce outside of a host cell;
their reproduction is entirely reliant on intracellular resources
- e.g. viruses
Virion - Answers the form a virus takes when not inside the host - a complete virus particle
Composition of a virion - Answers 1. genetic material - DNA or RNA
2. capsid - the protein coat
3. envelope - some viruses have a layer of lipids surrounding the protein coat
Virus-first theory - Answers viruses are ancestral to cells
- viruses evolved from mixtures of macromolecules before the first cells appeared on earth
- viruses existed as self-replicating units in a pre-cellular world
Escape theory - Answers cells came before viruses
- viruses are derived from bits of cellular RNA and/or DNA fragments that leaked from cells
, - when these fragments acquire a protein coat they can become independent entities with the
ability to interact with other cells
Reduction theory - Answers cells came before viruses
- viruses come from small primordial cells that lost cellular elements over the course of
evolution, but maintained their genetic material and certain elements needed for replication
Viral genome integration or lysogeny - Answers When a virus is capable of incorporating into the
host genome
Biological classification - Answers Life, Domain, Kingdom, Phylum, Class, Order, Family, Genus,
Species
Bacterial classification - Answers Kingdom, Phylum, Class, Order, Family, Genus, Species
Viral classification - Answers Order, family, subfamily, genus, species
Extremophiles - Answers organisms that live in harsh environments - may contribute to the
genetic information that confers successful infection strategies to pathogens
Selective pressure - Answers any phenomena that alters the behaviour and fitness of a living
organism in its environment
- if a mutation/acquisition occurs that confers a selective advantage, the cell will outcompete its
sisters and its lineage will eventually become the predominant cell type
Hyperthermophilic microbes - Answers thrive in super hot temperature
- e.g. grand prismatic hot spring
Four phyla of the human microbiome - Answers actinobacteria, bacteroidetes, firmicutes,
proteobacteria
Actinobacteria - Answers group of Gram-positive bacteria that are aerobic and mostly found in
soil
Bacteroidetes - Answers diverse Gram-negative phylum which have colonized virtually all types
of habitats on earth
Firmicutes - Answers phylum of bacteria which are Gram-positive and can often form
endospores
Proteobacteria - Answers major Gram-negative phylum, includes a diverse array of bacteria
2 types of bacteria in the human microbiome - Answers pathogenic and commensal
Pathogenic bacteria - Answers have the ability to cause infection
Three domains of life - Answers Bacteria, Archaea, Eukaryota
If a eukaryote has a membrane-enclosed nucleus, a prokaryote has: - Answers a nucleoid, not
membrane enclosed
If a eukaryote has lysosomes/peroxisomes, a prokaryote has: - Answers not present
If a eukaryote has an endoplasmic reticulum/golgi apparatus, a prokaryote has: - Answers not
present
If a eukaryote has a mitochondria, a prokaryote has: - Answers not present
Bacteria - Answers Domain of unicellular prokaryotes that have cell walls containing
peptidoglycan
Archaea - Answers Domain of unicellular prokaryotes that have cell walls that do not contain
peptidoglycan
Eukaryota - Answers Domain of organisms that contain a nucleus and other membrane
enclosed organelles
endosymbiont hypothesis - Answers eukaryotes evolved from prokaryotes, based on the
similarities found between bacteria and mitochondria
Symbiosis - Answers the living together to close association of two dissimilar organisms, each
being known as a symbiont
Differences between mitchondria+chloroplast and other organelles - Answers contain their own
DNA and have a distinct translation system
a-proteobacteria - Answers a subgroup of proteobacteria, which are a large group of eubacteria,
primarily Gram-negative, that 16S rRNA sequence comparisons show to be phylogenetically
related
Archezoan Scenario - Answers A primitive amitochondrial eukaryote cell phagocytosed as an a-
protobacterium - leading to the evolution of the mitochondrion
symbiogenesis scenario - Answers A single endosymbiotic event involving the uptake of an a-
protobacterium by an archaeal cell led to the generation of the mitochondria, followed by the
evolution of the nucleus and compartmentalization of the eukaryotic cell
Phylogeny - Answers the evolutionary history of a group of organisms
Phylogenetic tree of life - Answers compares the rRNA sequences between organisms
Comparing the domains of life: nucleus - Answers bacteria: no
,archaea: no
eukaryota: yes
Comparing the domains of life: RNA polymerase - Answers bacteria: 3-4 subunits
archaea: 8-12 subunits
eukaryota: 12-14 subunits
Comparing the domains of life: Ribosomes - Answers bacteria: 70S
archaea: 70S
eukaryota: 80S
Comparing the domains of life: cell wall - Answers bacteria: murein (peptidoglycan)
archaea: no murein
euakryota: no murein
Phylogenomic tree of life - Answers Tree of life based on complete genomes of organisms
horizontal gene transfer - Answers the movement of genetic material between organisms other
than via vertical transmission (parent to child)
Obligate intracellular parasite - Answers A parasite that cannot reproduce outside of a host cell;
their reproduction is entirely reliant on intracellular resources
- e.g. viruses
Virion - Answers the form a virus takes when not inside the host - a complete virus particle
Composition of a virion - Answers 1. genetic material - DNA or RNA
2. capsid - the protein coat
3. envelope - some viruses have a layer of lipids surrounding the protein coat
Virus-first theory - Answers viruses are ancestral to cells
- viruses evolved from mixtures of macromolecules before the first cells appeared on earth
- viruses existed as self-replicating units in a pre-cellular world
Escape theory - Answers cells came before viruses
- viruses are derived from bits of cellular RNA and/or DNA fragments that leaked from cells
, - when these fragments acquire a protein coat they can become independent entities with the
ability to interact with other cells
Reduction theory - Answers cells came before viruses
- viruses come from small primordial cells that lost cellular elements over the course of
evolution, but maintained their genetic material and certain elements needed for replication
Viral genome integration or lysogeny - Answers When a virus is capable of incorporating into the
host genome
Biological classification - Answers Life, Domain, Kingdom, Phylum, Class, Order, Family, Genus,
Species
Bacterial classification - Answers Kingdom, Phylum, Class, Order, Family, Genus, Species
Viral classification - Answers Order, family, subfamily, genus, species
Extremophiles - Answers organisms that live in harsh environments - may contribute to the
genetic information that confers successful infection strategies to pathogens
Selective pressure - Answers any phenomena that alters the behaviour and fitness of a living
organism in its environment
- if a mutation/acquisition occurs that confers a selective advantage, the cell will outcompete its
sisters and its lineage will eventually become the predominant cell type
Hyperthermophilic microbes - Answers thrive in super hot temperature
- e.g. grand prismatic hot spring
Four phyla of the human microbiome - Answers actinobacteria, bacteroidetes, firmicutes,
proteobacteria
Actinobacteria - Answers group of Gram-positive bacteria that are aerobic and mostly found in
soil
Bacteroidetes - Answers diverse Gram-negative phylum which have colonized virtually all types
of habitats on earth
Firmicutes - Answers phylum of bacteria which are Gram-positive and can often form
endospores
Proteobacteria - Answers major Gram-negative phylum, includes a diverse array of bacteria
2 types of bacteria in the human microbiome - Answers pathogenic and commensal
Pathogenic bacteria - Answers have the ability to cause infection
