Similar structures are present in the embryos of fish, salamanders, turtles, chickens and pigs. in fish, these structures develop into gills but in the other organisms they either disappear or develop into other body parts later in embryonic development. which of these statements below best explains the presence of these structures in the embryos of all five species? a) the embryos of the five species are similar in size. b) breathing structures are similar among the young of the five species. c) the five species have a common ancestor with these embryonic structures. d) the reproductive mechanisms are similar among the adults of the three species.

The correct answer is C) The five species have a common ancestor with these embryonic structures.

Explanation:

These species have a common ancestor that reflects in their embryonic appearance. This would explain why they have similar features in this stage and how they develop in similar ways.

step 1: initiation

initiation is the beginning of transcription. it occurs when the enzyme rna polymerase binds to a region of a gene called the promoter. this signals the dna to unwind so the enzyme can ‘‘read’’ the bases in one of the dna strands. the enzyme is now ready to make a strand of mrna with a complementary sequence of bases.

step 2: elongation

elongation is the addition of nucleotides to the mrna strand. rna polymerase reads the unwound dna strand and builds the mrna molecule, using complementary base pairs. there is a brief time during this process when the newly formed rna is bound to the unwound dna. during this process, an adenine (a) in the dna binds to an uracil (u) in the rna.

step 3: termination

termination is the ending of transcription, and occurs when rna polymerase crosses a stop (termination) sequence in the gene. the mrna strand is complete, and it detaches from dna.

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