Question

na contains instructions for making proteins, but dna is confined to the nucleus. rnas job to copy instructions from dna and carry them to other parts of the cell.
rna is created in the nucleus by using a section of dna as a template. first, the dnas hydrogen bonds are broken to split, or \unzip,\ the molecule into two strands. then, rna nucleotides are brought in to pair with the dna nucleotides according to the rules of complementary base pairing. but, since rna does not contain thymine, uracil pairs with adenine.
this model shows how rna nucleotides pair with dna nucleotides.
image: diagram of dna-rna pairing with nitrogenous bases (adenine, thymine, guanine, cytosine, uracil), phosphate group, ribose sugar, hydrogen bond
complete the paragraph to summarize how an rna molecule is created.
first, a section of the dna molecule is dropdown. then, rna nucleotides are brought in to pair with the dna nucleotides. according to the rules of complementary base pairing, dropdown pairs with thymine, and guanine pairs with dropdown. but rna contains the nitrogenous base uracil instead of dropdown. uracil pairs with dropdown.

Explanation:

1. From the text: "First, the DNA's hydrogen bonds are broken to split, or 'unzip,' the molecule into two strands" → first blank: unzipped.
2. Complementary base pairing rules (DNA - DNA or DNA - RNA template): A (adenine) pairs with T (thymine) in DNA - DNA, and in DNA - RNA pairing (RNA synthesis), A in RNA would pair with T in DNA (but RNA uses U instead of T for pairing with A). For G - C: guanine (G) pairs with cytosine (C) (consistent in DNA and DNA - RNA pairing).
3. RNA has uracil (U) instead of thymine (T) → fourth blank: thymine (T).
4. Uracil (U) pairs with adenine (A) (since RNA can’t use T, U pairs with A) → last blank: adenine (A).

Answer:

First, a section of the DNA molecule is \(\boldsymbol{\text{unzipped}}\) (or "split" as per the text: "hydrogen bonds are broken to split, or 'unzip,' the molecule into two strands"). Then, RNA nucleotides are brought in to pair with the DNA nucleotides. According to the rules of complementary base pairing, \(\boldsymbol{\text{adenine (A)}}\) pairs with thymine (T), and guanine (G) pairs with \(\boldsymbol{\text{cytosine (C)}}\). But RNA contains the nitrogenous base uracil (U) instead of \(\boldsymbol{\text{thymine (T)}}\). Uracil pairs with \(\boldsymbol{\text{adenine (A)}}\).