Eukaryotic sexual life cycles show tremendous variation. of the following elements, which do all sexual life cycles have in common? i. alternation of generations ii. meiosis iii. fertilization iv. gametes v. spores

II. meiosis

III. fertilization

IV. gametes

Explanation:

Gamete formation and fertilization are the processes performed by all the sexually reproducing organisms. Gametes are the cells that are formed in the male and female sexual organs of these organisms. Formation of gametes occurs by meiosis and therefore, the gametes of a diploid organism are always haploid.

Male and female gametes fuse during the process of fertilization and form the zygote which in turn divide repeatedly to produce an embryo. For instance, sperms and eggs are the male and female gametes that are formed in testes and ovaries of male and female human individuals respectively. The fusion of sperm and egg produces a zygote that finally develops into a young one.  

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.