At what stage of the meiotic cell cycle and during what chromosomal configuration does crossing over occur?
A) during bivalent formation, after synapsis of homologous chromosomes, and before the end of prophase I
B) in S phase of meiosis
C) at the four-strand stage of meiosis, after synapsis of homologous chromosomes, and before the end of prophase I
D) during synapsis in prometaphase
E) during synapsis at the four-strand stage of meiosis
Answer: C
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Alexander Oparin hypothesized that living cells evolved from coacervates. What was the "boundary" material of the coacervates Oparin made, and how does this boundary differ from present day liposome membranes?
A. Oparin used a phospholipid bilayer to build the coacervates, it is the same as the bilayer found in present day liposomes. B. Oparin's coacervates were surrounded by a tight skin of water molecules, the same as present day liposomes. C. Oparin's coacervates were surrounded by carbohydrates and lipids, unlike present day liposomes which have a carbohydrate membrane only. D. Oparin's coacervates were surrounded by a tight skin of water molecules; present day liposomes have a phospholipid bilayer for their membrane. E. Starch was the main component in Oparin's coacervate boundry; liposomes also use mainly carbohydrates for their membrane.
The taxonomic classification order, from least specific to most specific is:
a. domain, kingdom, phylum, class, family, order, genus, species. b. domain, kingdom, class, phylum, order, family, genus, species. c. domain, kingdom, order, class, phylum, family, genus, species. d. domain, kingdom, phylum, class, order, family, genus, species.
Which of the following statements is NOT TRUE?
a. Photons are packages of solar energy. b. Each photon consists of a fixed amount of energy. c. The least energetic photons travel in longer wavelengths. d. Photons with different energy levels are perceived as exhibiting different colors. e. Photons of visible light have wavelengths longer than 750 nanometers.
What was the approximate size of the human population in the year 2008?
A) 1.6 billion B) 2.6 billion C) 3.6 billion D) 6.6 billion E) 10 billion