A group of turtles is washed ashore on an island and no longer breeds with any turtles other than those on the island. After centuries of isolation, they no longer interbreed with the original species.
This situation is best described by the term:
A. allopatric speciation.
B. migration.
C. phylogenetic speciation.
D. genetic drift.
E. natural selection.
Which of the following was observed by Erwin Chargaff?
A. Base composition of DNA does not vary from one species to another.
B. The DNA isolated from different tissues of the same species all have the same base composition.
C. Base composition changes as the organism ages.
D. In all species, the number of adenines equals the number of guanines.
E. In all species, A + T = G + C.
Which one of the following is an exception to the rules of the genetic code?
A. Specific codons specify the same amino acids in Escherichia coli cells as inhuman cells.
B. The codon UGA is a stop codon in the mitochondria of higher plants.
C. A selenocysteine amino acid is incorporated into proteins in response to a UAG codon.
D. The cell only requires 32 different tRNAs to recognize 61 different codons.
Sidney Brenner found bacteriophage T4 point mutants in which a protein was prematurely terminated. The premature termination point of the protein was different in different mutants.
When he determined where the protein synthesis terminated for each mutant, in every case the next amino acid of the protein would have been a glutamine, lysine, glutamic acid, tyrosine, or serine. What is the unique similarity of these amino acids or their codons that would play a role in the premature termination of translation in the mutant protein gene?
A. Each of the amino acids has an R-group containing an amine, hydroxyl, or carboxyl group.
B. Each of the codons for these amino acids contains either U or G.
C. Each of the codons for these amino acids could be changed to UAG with a single nucleotide mutation.
D. Each of the amino acids is polar and charged.
The transposon sleeping beauty is:
A. a transposon from fish that was reactivated by mutation.
B. a transposon from fish that was reactivated by introducing a plasmid that had a functional transposase.
C. an artificially constructed transposon based on sequence comparisons of numerous inactive Tc1/mariner transposons.
D. a retrotransposon of humans.
E. a complex transposon that can move from cell to cell.