Showing posts with label Maths. Show all posts
Showing posts with label Maths. Show all posts

Monday, 5 October 2009

Protein sequence to DNA - Degeneracy calculation

I have had some questions about the reverse translation of protein to DNA and degeneracy...

The protein sequence is THERIGHTREADINGFRAME

It is 20 amino acids, and therefore, you will need 60 bases to encode it. So....

Protein Seq:  T  H  E  R  I  G  H  T  R  E  A  D  I  N  G  F  R  A  M  E 
DNA Seq:     ACNCAYGARMGNATHGGNCAYACNMGNGARGCNGAYATHAAYGGNTTYMGNGCNATGGAR    
Full DNA:    ACACACGAACGAATAGGACACACACGAGAAGCAGACATAAACGGATTCCGAGCAATGGAA
               T  T  G  T  C  T  T  T  T  G  T  T  C  T  T  T  T  T     G
               G        G  T  C     G  G     C     T     C     G  C
               C        C     G     C  C     G           G     C  G
                      AGG            AGG                     AGG
                        A              A                       A
Number codons: 4  2  2  6  3  4  2  4  6  2  4  2  3  2  4  2  6  4  1  2
So, 4 x 2 x 2 x 6 x 3 x 4 x 2 x 4 x 6 x 2 x 4 x 2 x 3 x 2 x 4 x 2 x 6 x 4 x 1 x 2 = 2,038,431,744 or 2 x 109 possible DNA sequences would encode the protein sequence.

This is a big number; however, compared to the total number of possible DNA sequences you could have for a 60-base sequence, it is small.

The total number of DNA sequences you could have for a 60 base sequence is 4 x 4 x 4.... sixty times, or 460, which is equal to 1.3 x 1036 possible sequences. Of those 1.3 x 1036 sequences only 2,038,431,744 would encode THERIGHTREADINGFRAME. Or in percentage terms, (2,038,431,744 / 1.3 x 1036) x 100 = 0.0000000000000000000000002% (2 x 10-25%) of all the possible sequences would encode THERIGHTREADINGFRAME.

You may find the following video useful where I explain the above:


If you would like to support my blogging efforts, then please feel free to buy me a coffee at https://www.buymeacoffee.com/drnickm

Additional Resources

Sunday, 4 October 2009

Calculating Dilutions

I have received a number of emails about dilution calculations.

The type of question is:

You have been asked to dilute a 10 mg/ml solution to give 5 ml of a 1.5 mg/ml solution.

How many ml of water would you use?

How many ml of the stock protein solution would you use?

The way I would work this out is by saying that 5 ml of 1.5 mg/ml contains 5 x 1.5 mg = 7.5 mg.

If the stock is 10 mg/ml then I need to take a volume that would give 7.5 mg. So, the number of ml of the stock I need is 7.5 / 10 = 0.75 ml (that is, 0.75 ml of a 10 mg/ml solution contains 7.5 mg).

Therefore, I have 0.75 ml of the stock, and the final volume is 5 ml, so we need to add 5 - 0.75 = 4.25 ml of water.

The answer:

How many ml of water would you use? 4.25 ml

How many ml of the stock protein solution would you use? 0.75 ml

Although I prefer to work it out as above you can use a formula:

M1V1 = M2V2

Where:
M1 = Concentration 1
V1 = Volume 1
M2 = Concentration 2
V2 = Volume 2
Therefore:
M1 = Concentration 1 = 10 mg/ml
V1 = Volume 1 = Unknown X
M2 = Concentration 2 = 1.5 mg/ml
V2 = Volume 2 = 5 ml

or:
M1V1 = M2V2 10 mg/ml x Unknown X = 1.5 mg/ml x 5 ml

Rearranging to solve for Unknown X:

Unknown X = (1.5 mg/ml x 5 ml) / 10 mg/ml Therefore, Unknown X = 0.75 ml

Using the formula is the same as the first solution, but in the first solution, I don't have to remember the formula....

If you struggle with 'Science Maths' then you may like to look at Maths4Biosciences.

If you would like to support my blogging efforts, then please feel free to buy me a coffee at https://www.buymeacoffee.com/drnickm

Additional Resources