AP BIOLOGY

Detailed explanation-1: -Definition. The nucleolus is a spherical structure found in the cell’s nucleus whose primary function is to produce and assemble the cell’s ribosomes. The nucleolus is also where ribosomal RNA genes are transcribed.

Detailed explanation-2: -Answer and Explanation: The correct answer is (a): nucleus. In eukaryotic cells, DNA is located inside the nucleus. The transcription of mRNA takes place inside the nucleus because this process requires information on DNA to be copied.

Detailed explanation-3: -mRNA is synthesized in the nucleus using the nucleotide sequence of DNA as a template. This process requires nucleotide triphosphates as substrates and is catalyzed by the enzyme RNA polymerase II. The process of making mRNA from DNA is called transcription, and it occurs in the nucleus.

Detailed explanation-4: -The genes that encode ribosomal proteins are transcribed outside of the nucleolus by RNA polymerase II, yielding mRNAs that are translated on cytoplasmic ribosomes. The ribosomal proteins are then transported from the cytoplasm to the nucleolus, where they are assembled with rRNAs to form preribosomal particles.

Detailed explanation-5: -There are a few places in the cell in which mRNA is found: the nucleus, the cytoplasm, and the endoplasmic reticulum. Transcription happens in the nucleus in eukaryotic cells, and so the original transcript of mRNA can be found in the nucleus.