PercyGrunwald's solution to RNA Transcription on the Elixir track

Instructions

Test suite

Solution

Given a DNA strand, return its RNA complement (per RNA transcription).

Both DNA and RNA strands are a sequence of nucleotides.

The four nucleotides found in DNA are adenine (A), cytosine (C), guanine (G) and thymine (T).

The four nucleotides found in RNA are adenine (A), cytosine (C), guanine (G) and uracil (U).

Given a DNA strand, its transcribed RNA strand is formed by replacing each nucleotide with its complement:

G -> C
C -> G
T -> A
A -> U

Running tests

Execute the tests with:

$ elixir rna_transcription_test.exs

Pending tests

In the test suites, all but the first test have been skipped.

Once you get a test passing, you can unskip the next one by commenting out the relevant @tag :pending with a # symbol.

For example:

# @tag :pending
test "shouting" do
  assert Bob.hey("WATCH OUT!") == "Whoa, chill out!"
end

Or, you can enable all the tests by commenting out the ExUnit.configure line in the test suite.

# ExUnit.configure exclude: :pending, trace: true

If you're stuck on something, it may help to look at some of the available resources out there where answers might be found.

Source

Hyperphysics http://hyperphysics.phy-astr.gsu.edu/hbase/Organic/transcription.html

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

rna_transcription_test.exs

if !System.get_env("EXERCISM_TEST_EXAMPLES") do
  Code.load_file("rna_transcription.exs", __DIR__)
end

ExUnit.start()
ExUnit.configure(exclude: :pending, trace: true)

defmodule RNATranscriptionTest do
  use ExUnit.Case

  # @tag :pending
  test "transcribes guanine to cytosine" do
    assert RNATranscription.to_rna('G') == 'C'
  end

  @tag :pending
  test "transcribes cytosine to guanine" do
    assert RNATranscription.to_rna('C') == 'G'
  end

  @tag :pending
  test "transcribes thymidine to adenine" do
    assert RNATranscription.to_rna('T') == 'A'
  end

  @tag :pending
  test "transcribes adenine to uracil" do
    assert RNATranscription.to_rna('A') == 'U'
  end

  @tag :pending
  test "it transcribes all dna nucleotides to rna equivalents" do
    assert RNATranscription.to_rna('ACGTGGTCTTAA') == 'UGCACCAGAAUU'
  end
end

defmodule RNATranscription do
  @dna_nucleotide_to_rna_nucleotide_map %{
    # `G` -> `C`
    71 => 67,

    # `C` -> `G`
    67 => 71,

    # `T` -> `A`
    84 => 65,

    # `A` -> `U`
    65 => 85
  }

  @doc """
  Transcribes a character list representing DNA nucleotides to RNA

  ## Examples

  iex> RNATranscription.to_rna('ACTG')
  'UGAC'
  """
  @spec to_rna([char]) :: [char]
  def to_rna(dna) do
    dna
    |> Enum.map(&get_rna_for_dna/1)
  end

  defp get_rna_for_dna(dna_nucleotide) do
    @dna_nucleotide_to_rna_nucleotide_map[dna_nucleotide]
  end
end

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PercyGrunwald's solution

to RNA Transcription in the Elixir Track