Question

Answer the following questions based on this codingstrand of DNA:                                    

                                    5’ GGCCATGACAGAGGAGCAAAAGTTATTGCT 3’

Drennan et al. (1996) identified several mutations in this enzyme that result in methylmalonic acidemia (MMA). One of those mutations is a C to A at base pair 1904 in the coding strand of DNA (bold and italicized in the template strand).

1. Write the unique coding strand of DNA for this patient and highlight the change you made. Write it 5’ to 3’.
2. Write the mRNA sequence for this patient and clearly highlight the change you made. Write it 5’ to 3’.
3. Write the amino acid sequence for this patient, highlight what differs from the normal (wildtype) sequence.
4. What type of mutation is this? (insertion, deletion, silent, nonsense,missense,or frameshift mutation? Explain your reasoning.

Answer 1

Answer-

According to the given question-

Here we have a coding strand of DNA:                                    

                                      5’ GGCCATGACAGAGGAGCAAAAGTTATTGCT 3’

complementary strand is -        3' CCGGTACTGTCTCCTCGTTTTCAATAACGA 5'

mRNA-    5’ GGCCAUGACAGAGGAGCAAAAGUUAUUGCU 3’

Amino acid sequence-N-terminal Gly - His- Asp- Arg -Gly - Ala - Lys -Val -Ile -Ala-     C- Terminal

When there is mutations in DNA coding strand such as C is replaced by A which means that pyrimidine base are replaced by purine bases this a type of transversion mutation , a type of point mutation.

After replacing C to A we get

coding strand of DNA- 5’ GGCCATGACAGAGGAGAAAAAGTTATTGCT 3’

we know that DNA is made up of two strand and both are complementary to each other . one strands is arranged as 5' to 3' direction while other strands as 3' to 5' direction.

So the other strand of this sequence will be -

coding strand of DNA- 5’ GGCCATGACAGAGGAGAAAAAGTTATTGCT 3’

                                3' CCGGTACTGTCTCCTCTTTTTCAATAACGA 5' - This strand called anti-sense strand and work as template for transcription of RNA. RNA contain uracil nitrogenous base instead of Thymine which is present in DNA and other bases are same.

Transcription is formation of RNA from DNA which occur in 5' to 3' direction.

So mRNA formed from the DNA sequence is

DNA -             3' CCGGTACTGTCTCCTCTTTTTCAATAACGA 5'

mRNA -         5’ GGCCAUGACAGAGGAGAAAAAGUUAUUGCU 3’

Amino acid sequence is - N-terminal-    Gly - His- Asp- Arg -Gly - Glu - Lys -Val -Ile -Ala-      C- Terminal

• There is difference in one amino acid which in wild type code for Alanine while after mutation it code for Glutamic acid
• This is a type of missense mutation because in wild type there was alanine amino acid present in the polypeptide chain which was changed into the glutamic acid which is different than alanine and coded by different sequence .