Scientists isolate cells in various phases of the cell cycle. They find a group of cells that have times more DNA than G1 phase cells. The cells of this group are _____
A) between the G1 and S phases in the cell cycle
B) in the G2 phase of the cell cycle
C) in the M phase of the cell cycle
D) in the S phase of the cell cycle
D
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Explain why some people fear genetically modified foods despite commercial organization claims that these foods are safe for human consumption
What will be an ideal response?
Lichens are a symbiotic relationship between which of the following?
a) a fungus and a liverwort b) a fungus and a moss c) two species of algae d) a fungus and algae e) two species of fungi
An extraterrestrial organism (ET) is discovered whose basic cell biology seems pretty much the same as that of terrestrial organisms except that it uses a different genetic code to translate RNA into protein
You set out to break the code by translation experiments using RNAs of known sequence and cell-free extracts of ET cells to supply the necessary protein-synthesizing machinery. In experiments using the RNAs below, the following results were obtained when the 20 possible amino acids were added either singly or in different combinations of two or three: RNA 1: 5?-GCGCGCGCGCGCGCGCGCGCGCGCGCGC-3? RNA 2: 5?-GCCGCCGCCGCCGCCGCCGCCGCCGCCGCC-3? Using RNA 1, a polypeptide was produced only if alanine and valine were added to the reaction mixture. Using RNA 2, a polypeptide was produced only if leucine and serine and cysteine were added to the reaction mixture. Assuming that protein synthesis can start anywhere on the template, that the ET genetic code is nonoverlapping and linear, and that each codon is the same length (like the terrestrial triplet code), how many nucleotides does an ET codon contain? (a) 2 (b) 3 (c) 4 (d) 5 (e) 6
Using the demographic terms presented in this chapter, compare and contrast the populations of highly
developed and less developed countries. What will be an ideal response?