Which simple machine can be described as a rope that is threaded through a wheel or disk? a. inclined plane b. pulley c. screw d. lever

Which simple machine can be described as a rope that is threaded through a wheel or disk?

The correct answer is B - Pulley

A pulley is a simple machine that is used to lift loads. It consists of a wheel on which a rope is placed and the rope is pulled by the person towards himself to lift the load that is tied on the other side of the rope. There are three main types of pulleys: fixed, movable, and compound.

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.