5. Bioengineers construct peptides with new functions by starting with a particu

Question

5. Bioengineers construct peptides with new functions by starting with a particular peptide, and then mutating the amino acid present at different positions. They then screen the resulting mutant peptide for the desired function. Suppose the starting peptide is 10 amino acids long. Recall there are 20 amino acids.

a. How many peptides will need to be screened if the amino acids at positions three, seven, and eight are all mutated?

b. If we consider all possible mutants for the amino acid at one position only, but this can be at any of the 10 positions, how many new peptides will need to be screened?

7. A palindrome is a word, such as 'radar', that reads the same forwards and backwards. How many different five-letter palindromes are possible if they do not need to be real words?

10. Certain blood types can be classified as either A, B, AB, or O, and by whether they are Rh+ or Rh. How many different blood types are possible?

12. When DNA is decoded into protein the 'letters' of the DNA sequence are 'read' in ordered triplets. For example, the sequence 'ACGTACTTA' would be read as the three ordered triplets 'ACG,' 'TAC,' and 'TTA.' Each letter can be either G, T, C, or A and each distinct triplet can code for a different protein subunit called an amino acid. How many different amino acids can be coded for?

My Notas Ask Your Taachar Binengineers construct peptides with new tunctions by starting with a partiolar peptide, and then mutating the amina aid present at dirterent positions. They then screen the resulting mutant peptide for the desired function. St ppose the starting peptide is 1 acids long. Recall there are 20 amino acids amino a)How many peptides will need to be screerned if the amin acids at positions three, seven, and eight are all mutated? peptides ] rr vva consider all possibl mutants ror th amin, aid at one position only, but thR can be ar any of the 10 pnsitiona, h w many nav peptidas will need to b screened? peptides

Explanation / Answer

5a) There are three allowed position for changing amino acids. Out of the possible 20 amino acids, one is the correct and thus not a mutation. Therefore at each position, there are 19 possible mutations. Since it is a combination of 19 amino acids at 3 positions, hence, total peptides needed to be screened is:

19*19*19= 6859 peptides.

b)Since there are 10 positions, and 19 mutations possibe at each positions. Therefore the total peptides to be screened are:

(19 per position)*10 positions = 190 peptides

7) There are 5 positions, and only the 1st three need to be computed, because 1st matches with the 5th and 2nd matches with the 4th. Thus at first three positions all 26 letters are allowed. Thus the number of possible palindromes becomes:

26*26*26*1*1 = 17576

10) Since there are two Rh blood groups possible per blood type, therefore possible blood types are:

(A + B + AB +O ) *(Rh+ or Rh-)

= 4*2

= 8 Blood types

12) For the give sequence "ACGTACTTA", there are possible 3 open reading frames(ORFs) from 5'-3', and 3 ORFs from 3'-5'.

For 5'-3' ORFs are :

For 3'-5' ORFs are:

Thus in total the total number of amino acids that can be coded from all 6 ORFs are 14 amino acids.

From only one of the of the ORFs is 7 amino acids.

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