Micro test 2 ch. 18 MCAT practice test

A NASA ecologist wants to design an instrument to send to Mars on the next space probe to determine whether living organisms ever carried out carbon fixation on that planet. Suggest an assay that she could use on Martian soil samples. 34S/35S stable isotope analysis 13C/12C stable isotope analysis MAR-FISH NanoSIMS

13C/12C stable isotope analysis

When measuring microbial community metabolic activity, __________ is always necessary. DNA extraction and sequencing a killed control enrichment culture radioisotopes

a killed control

By isolating total community RNA, using reverse transcriptase to make cDNA copies of it, and then sequencing the cDNA, ecologists can __________. A-determine the community genome translation at the moment of sampling B-determine the community metabolic activity at the moment of sampling C-determine the community genomic potential at the moment of sampling D-determine the community genome expression at the moment of sampling

determine the community genome expression at the moment of sampling

The phylogenetic analysis of complex microbial communities often targets small subunit (SSU) ribosomal RNA genes. This is because rRNA is found in all organisms and __________. A-is highly conserved over evolutionary time B-has more genes than mRNA C-is easier to extract from samples D-is made by cells only at certain times

is highly conserved over evolutionary time

Enrichment cultures are often effective for isolating bacteria from complex communities in natural samples because they __________. A-select against certain bacteria B-select both for and against certain bacteria C-select for certain bacteria D-do not select for or against any bacteria; they help every organism to grow

select both for and against certain bacteria

When Beijerinck enriched for nitrogen fixers, he inoculated soil into two types of liquid media: one containing mineral salts and mannitol but no nitrogen source (flask A), and one containing mineral salts, mannitol, and an ammonium salt (flask B). After incubation in the presence of air, what types of organisms did he find in each flask? A-Flask A contained ammonium utilizers, and flask B contained nitrogen fixers that could grow with or without the presence of ammonium. B-Flask A contained nitrogen fixers that could grow both with and without ammonium; flask B did not contain nitrogen fixers but did contain organisms that could use ammonium. C-Flask A contained nitrogen fixers that could not tolerate the presence of ammonium; flask B contained ammonium utilizers. D-Flask A contained ammonium utilizers and flask B contained nitrogen fixers that could not tolerate the presence of ammonium.

Flask A contained nitrogen fixers that could grow both with and without ammonium; flask B did not contain nitrogen fixers but did contain organisms that could use ammonium.

Phylogenetic analysis of microbial communities in nature using various PCR techniques has revealed that most phylotypes have not been grown in laboratory culture, due in part to __________. A-the uncultured organisms' being rare in the community B-poor technique C-enrichment bias D-lack of sufficient sampling of the community

enrichment bias

Genes that change over evolutionary time as organisms diverge are called orthologs. Organisms with identical or very similar orthologous genes belong to the same __________. phylotype phenotype ribotype genotype

phylotype

Metagenomics involves the analysis of a microbial community by __________. A-generating a complete sequence of the genomes of all of the organisms in an environment B-sequencing all of the community RNA in an environment C-generating a phylogenetic tree based on all of the versions of a gene in an environment D-sampling and sequencing all of the genes in an environment

sampling and sequencing all of the genes in an environment

Metagenomics is a more sensitive analysis of community diversity than rRNA-based analyses because __________. A-rRNA genes are not found in all of the organisms present in the environment B-the extraction of the DNA from the environmental samples is more efficient C-genes do not have to be amplified by PCR before being sequenced D-more clone libraries can be assembled

genes do not have to be amplified by PCR before being sequenced