Question

during transcription in eukaryotes, a type of rna polymerase called rna polymerase ii moves along the template strand of the dna in the 3-5 direction. however, for any given gene, either strand of the double-stranded dna may function as the template strand. for any given gene, what ultimately determines which dna strand serves as the template strand?
view available hint(s)
which of the two strands of dna carries the rna primer
the location of specific proteins (transcription factors) that bind to the dna
the base sequence of the genes promoter
the location along the chromosome where the double-stranded dna unwinds
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part c - rna processing
after transcription begins, several steps must be completed before the fully processed mrna is ready to be used as a template for protein synthesis on the ribosomes. which three statements correctly describe the processing that takes place before a mature mrna exits the nucleus?
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a cap consisting of a modified guanine nucleotide is added to the 5 end of the pre-mrna.
a poly-a tail (50-250 adenine nucleotides) is added to the 3 end of the pre-mrna.
coding sequences called exons are spliced out by ribosomes.
a translation stop codon is added at the 3 end of the pre-mrna.
noncoding sequences called introns are spliced out by molecular complexes called spliceosomes.

Explanation:

• A cap consisting of a modified guanine nucleotide is added to the 5' end of the pre - mRNA: This is part of mRNA processing in eukaryotes. The 5' cap helps in mRNA stability, export from the nucleus, and initiation of translation.
• A poly - A tail (50 - 250 adenine nucleotides) is added to the 3' end of the pre - mRNA: The poly - A tail also contributes to mRNA stability and is involved in export from the nucleus.
• Noncoding sequences called introns are spliced out by molecular complexes called spliceosomes: Splicing removes introns (non - coding regions) from the pre - mRNA, leaving only exons (coding regions) in the mature mRNA.

The other options are incorrect:

• A translation stop codon is not added at the 3' end of the pre - mRNA during RNA processing. Stop codons are part of the coding sequence in the mRNA (originating from the DNA template) and are not added as a post - transcriptional modification in this way.
• Coding sequences (exons) are not spliced out. It is the non - coding introns that are removed.

Answer:

A cap consisting of a modified guanine nucleotide is added to the 5' end of the pre - mRNA, A poly - A tail (50 - 250 adenine nucleotides) is added to the 3' end of the pre - mRNA, Noncoding sequences called introns are spliced out by molecular complexes called spliceosomes.