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to RNA Transcription in the Crystal Track

Published at Nov 21 2018 · 0 comments
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

Setup

Follow the setup instructions for Crystal here:

http://exercism.io/languages/crystal

More help installing can be found here:

http://crystal-lang.org/docs/installation/index.html

Making the Test Suit Pass

Execute the tests with:

$ crystal spec

In each test suite all but the first test have been skipped.

Once you get a test passing, you can unskip the next one by changing pending to it.

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_spec.cr

require "spec"
require "../src/*"

describe "RnaComplement" do
  describe "#of_dna" do
    it "correctly transcribes cytosine to guanine" do
      RnaComplement.of_dna("C").should eq "G"
    end

    pending "correctly transcribes guanine to cytocine" do
      RnaComplement.of_dna("G").should eq "C"
    end

    pending "correctly transcribes thymine to adenine" do
      RnaComplement.of_dna("T").should eq "A"
    end

    pending "correctly transcribes adenine to uracil" do
      RnaComplement.of_dna("A").should eq "U"
    end

    pending "correctly transcribes all dna nucleotides to their rna compliment" do
      RnaComplement.of_dna("ACGTGGTCTTAA").should eq "UGCACCAGAAUU"
    end
  end
end
module RnaComplement
  extend self

  def of_dna(dna : String) : String
    String.build { |s|
      dna.each_char { |c|
        case c
        when 'C'
          s << 'G'
        when 'G'
          s << 'C'
        when 'T'
          s << 'A'
        when 'A'
          s << 'U'
        else
          raise ArgumentError.new "invalid char in dna string. expected [CGTA]*"
        end
      }
    }
  end

end

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