Problems on mutational changes

Problem B.1

Construct a matrix of the set {A, C, T, G} to illustrate the characteristic of the transition and transversion mutations.

(Hint: You may use a score of 100 % to depict the element of the matrix pertinent to no mutation - for example for 100% for A-to-A as shown; and, use prorated percentages to represent other elements illustrating the characteristic as above. The spontaneous base substitutions ratio of transitions to transversions is approximately 2:1. Therefore each transition should have a probability of 2/3 and each transversion 1/3).

Answer:

Problem # B.2 (a)

A strand is presumably mutated at a location underlined in the sequences shown below. In each case, (i) write down the eventual resulting strand for the following additional mutations happening in succession:

1) Inversion   of some subsequence part

2) Deletion of some subsequence part

3) Transpose ofsome subsequence part

4) Duplication of a base-pair  in the sequence

5) Point mutation of one base into another

 (Hint: The answers may depend on subjective selection as required)

a).....TTAAGGGGGGCCTTTTGAAA.... 

Example answer: (5) GGGG → GGCG

(b)....,,AAAAGGGGGGCCTTGGGACC.... 

(c) ......CCAAGGGTGTCCTTTTGAGG.... 

(ii) In each case, also write down the corresponding final resulting duplex strands at preRNA level

1. GGCG

Example answer: CCGC

2. AAATAA

3. TCCT

4. CGTTA

Problem B. 2(b)

Consider an ancestral sequence:

...ACCCTAC ...

Suppose a sequence of changes occur on this segment as follows: Single substitution, no change, multiple substitutions, back substitution, parallel substitutions, coincidental substitutions and convergent substitutions.                

Write down two possible resulting sequences.

 1) Initial -        ACCCTAC

Single Sub -           (A→G)CCCTAC (Example answer)

No Change -         

Multiple Sub -      

Back Sub -           

Parallel Sub -        

Coincidental Sub-

Convergent Sub -

2) Initial -    ACCCTAC

Single Sub -          

No Change -         

Multiple Sub -       A(C→T→A)CCTTC (Example answer)

Back Sub -           

Parallel Sub -        

Coincidental Sub-

Convergent Sub -

Problem B.3

Given a sequence:

X: 5' - TAC GGA TCG AAT GCT CCC GTA ATC - 3'

Suppose the following mutations have occurred in succession: A single point mutation, deletion of a triplet and duplication of a triplet twice in succession; and, the resulting complementary strand is found to be:

Y: 3' - ATG CCT AAC TTA CGG CAT CAT CAT TAG - 5'

Find

Single Point Mutation - (Example answer: Highlight in YELLOW.  In triplet 3, the second base C was changed to T.  ....GGA TCG .... to  ....CCT AAC ....)

Deletion of a Triplet - Highlight in RED.

Duplication of a Triplet - Highlight in GREEN.