Let's solve this step by step: --- ### **Step 1: Identify the Template Strand and Direction of Synthesis** - The template strand for RNA synthesis is the **3' to 5'** strand (top strand in your image). - RNA is synthesized **5' to 3'**, and the first nucleotide added is complementary to the **+1** position (the first base after the +1 arrow on the template strand). --- ### **Step 2: Find the First Four Template Bases at the +1 Site** - The arrow points just before "**CAA...**" on the **3' to 5'** strand. - The first four bases on the template strand after +1 are: **C, A, A, T** (read 3' to 5') --- ### **Step 3: Write the RNA Sequence (5' to 3') Using Complementary Base Pairing** - RNA uses **A, U, C, G** (U instead of T). - Pairing: - C → G - A → U - A → U - T → A So, the first four RNA nucleotides are: **G U U A** --- ### **Final Answer** **5' GUUA 3'**

The concept used in answering this question involves understanding the directionality of DNA and RNA strands, identifying the template strand's sequence at the transcription start site (+1 position), and applying complementary base pairing rules to determine the newly synthesized RNA nucleotides. Since transcription proceeds in the 5' to 3' direction on the RNA, we first locate the template strand's bases immediately downstream of the +1 site in the 3' to 5' direction, then determine their complementary RNA nucleotides, which are written in the 5' to 3' direction.

The concept used in answering this question revolves around the principles of transcription and nucleotide complementarity. During transcription, RNA polymerase synthesizes a complementary RNA strand in the 5' to 3' direction, using the DNA template strand as a guide. The template DNA strand is read in the 3' to 5' direction, and for each nucleotide on the template, a complementary RNA nucleotide is added: adenine (A) pairs with uracil (U) in RNA, thymine (T) pairs with adenine (A), cytosine (C) pairs with guanine (G), and guanine (G) pairs with cytosine (C). To determine the first four nucleotides to be synthesized, it is essential to identify the sequence of the DNA template strand immediately downstream of the transcription start site (+1). By reading this sequence from 3' to 5', we can find the next four bases, then apply complementary base pairing rules to find the corresponding RNA nucleotides, which are added in the 5' to 3' direction. This understanding of strand orientation, directionality, and base pairing is fundamental to accurately predicting the initial nucleotides in the RNA transcript.