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which process make meiotic cells genetically different and occurs during prophase i, but not during prophase ii?
fertilization
independent assortment
crossing over
chromosome replication
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Crossing over

Explanation:

During prophase I of meiosis, homologous chromosomes pair to form bivalents. The chromatids of bivalents may form intimate contact points called chiasmata. At the chiasmata breakage may occur and exchange of chromatids segments between non sister chromatids may take place. This is crossing over ad results in new gene combinations causing variations.

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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