All living things are divided into three domains: bacteria, archaea, and eukarya. They have several traits that are specific to each domain or shared across the domains.   Based on this information, what traits would the last universal common ancestor (LUCA) be expected to have? A. Nuclear envelope, introns in genes, and peptidoglycan in cell walls.   B. Histones associated with DNA, circular chromosome, and peptidoglycan in cell walls.   C. Unbranched hydrocarbons in membrane lipids, histones associated with DNA, and introns in genes.   D. Circular chromosome, unbranched hydrocarbons in membrane lipids, and one kind of RNA polymerase.

Which of the following statements accurately describes what we learned about HIV evolution?   a. HIV is more deadly in Northern Europe, but more transmissible in Africa. That is why there are more individuals infected with the illness in Africa.   b. HIV shares a most recently common ancestor with Simian Immunodeficiency Virus (SIV) such that SIV evolved as it host-switched from chimpanzees and gorillas into humans multiple times.   c. Drug development is exceedingly difficult because there are very few drug targets for HIV and AZT (a reverse transcriptase inhibitor) alone is the single most effective treatment for HIV.   d. Evolution of HIV virions within a person is quite slow such that a blood draw after 1 year of infection would reveal that every single virion would have the exact same sequence.

Which of the following schemes for molecular information flow never occurs in cellular life forms? a. DNA to rRNA b. mRNA to protein c. DNA to tRNA d. DNA to mRNA e. RNA to DNA

A scientist discovered a new group of unicellular organisms that lack mitochondria but possess an organelle related to the endoplasmic reticulum and is involved in energy production. The scientist hypothesizes that this organelle might be a missing link in the evolution of mitochondria. A) Do you agree with this hypothesis? Explain. B) Based on the available evidence, what is the most likely hypothesis for the origin of mitochondria? Provide four pieces of evidence to support this theory and justify why they are valid.