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4d47's solution

to RNA Transcription in the Crystal Track

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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
class RnaComplement
  def self.of_dna(strand : String) : String
    strand.tr("GCTA", "CGAU")
  end
end

What can you learn from this solution?

A huge amount can be learnt from reading other people’s code. This is why we wanted to give exercism users the option of making their solutions public.

Here are some questions to help you reflect on this solution and learn the most from it.

  • What compromises have been made?
  • Are there new concepts here that I could read more about to develop my understanding?