Molecular Final

Trichomonas vaginalis is an unusual protist because most lack introns. Why is this unusual?

T. vaginalis is a eukaryote. In most eukaryotes, introns (intervening sequences) are removed from RNA during RNA processing.

Organisms, such as some amoeba, are capable of cytoplasmic streaming. What type of cytoskeletal element is most important in this process?

microfilaments

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

Metagenomics involves the analysis of a microbial community by __________.

sampling and sequencing all of the genes in an environment

Metagenomics is a more sensitive analysis of community diversity than rRNA-based analyses because __________.

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

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.

13C/12C stable isotope analysis

Why is it generally more difficult to effectively treat systemic fungal infections than to treat bacterial infections?

Because fungi are eukaryotes, their cells are more similar to human cells and it is harder to target the fungal cells without causing harm to the human cells.

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?

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.

Giardia intestinalis (Giardia lamblia) is a protist that causes giardiasis. Its mitochondria do not have electron transport proteins and citric acid cycle enzymes. What can you infer from this information?

G. intestinalis uses fermentation.

What is one piece of evidence for the endosymbiotic hypothesis?

Mitchondria have 70S ribosomes.

Intermediate filaments are especially useful in identifying the origin of tumor cells. Why is this?

The materials making up different intermediate filaments differ in different cell types. By determining what components are present, it is possible to determine the tissue from which the cells originated, even if the cells have become highly undifferentiated.

What is one feature of fungi that distinguishes them from plants?

They can be dikaryotic.

Which of the following is true of mitochondr

They have their own DNA, mtDNA, which is inherited from the female parent.

Dictylostelium discoideum has a life cycle in which individual amoeba can aggregate, form a slug, migrate, and eventually form a fruiting body with a rigid stalk (containing cellulose) and a head. The cells in the head form spores that are released. This process occurs when the amoebae are starved. What is one reason that this process makes them so interesting to scientists?

This life cycle provides opportunities to study how cells differentiate.

When measuring microbial community metabolic activity, __________ is always necessary.

a killed control

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 __________.

enrichment bias

By isolating total community RNA, using reverse transcriptase to make cDNA copies of it, and then sequencing the cDNA, ecologists can __________.

etermine 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 __________.

is highly conserved over evolutionary time

Which of the following is the type of cytoskeletal element that includes the actin of muscle cells?

microfilaments

Enrichment cultures are often effective for isolating bacteria from complex communities in natural samples because they __________.

select both for and against certain bacteria