Two remnants of fetal structures are observable in the adult heart- the ligamentum arteriosum and the fossa ovalis. the fetal heart structures are called the ductus arteriosus and the foramen ovale, respectively. what common purpose did they serve as functioning fetal structures? a. they allowed blood to bypass the non-functional fetal lungs. b. they supplied blood to the immature fetal heart muscle. c. they provided support the the delicate tissues of the developing heart. d. they received maternal blood from the umbilical cord.

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.

what are the options? add them, then i will be glad to .

a

explanation: