Q29-27E - Organic Chemistry (Mcmurry)

Question

Question: From what DNA sequences were each of the mRNA codons in Problem 28-26 transcribed?

Step-by-Step Solution

Answer

In solution (a), the antisense DNA strand transcribed is $3^{\text{'}}-\text{T}-\text{T}-\text{A}-5^{\text{'}}$

In solution (b), the antisense DNA strand transcribed is $3^{\text{'}}-\text{C}-\text{T}-\text{C}-5^{\text{'}}$

In solution (c), the antisense DNA strand transcribed is ${\text{3}}^{\text{'}}-\text{A}-\text{G}-\text{G}-5^{\text{'}}$

In solution (d), the antisense DNA strand transcribed is $3^{\text{'}}-\text{G}-\text{T}-\text{A}-5^{\text{'}}$

Step 1: Introduction

The antisense strand of DNA is used to produce mRNA molecules. This sequence will have thymine instead of uracil and is complementary to the mRNA.

Step 2: Explanation for (a)

The mRNA molecules are made by transcribing the antisense strand of the DNA molecules.

The mRNA strand is,

$5^{\text{'}}-\text{A}-\text{A}-\text{U}-3^{\text{'}}$

The complementary antisense DNA strand is,

${\mathbf{3}}^{\mathbf{\text{'}}}\mathbf{-}\mathbf{\text{T}}\mathbf{-}\mathbf{\text{T}}\mathbf{-}\mathbf{\text{A}}\mathbf{-}{\mathbf{5}}^{\mathbf{\text{'}}}$

Step 3: Explanation for (b)

The mRNA molecules are made by transcribing the antisense strand of the DNA molecules.

The mRNA strand is,

$5^{\text{'}}-\text{G}-\text{A}-\text{G}-3^{\text{'}}$

The complementary antisense DNA strand is,

${\mathbf{\text{3}}}^{\mathbf{\text{'}}}\mathbf{-}{\mathbf{\text{C-T-C-5}}}^{\text{'}}$

Step 4: Explanation for (c).

The mRNA molecules are made by transcribing the antisense strand of the DNA molecules.

The mRNA strand is,

${\mathbf{\text{5}}}^{\mathbf{\text{'}}}\mathbf{-}\mathbf{\text{U}}\mathbf{-}\mathbf{\text{C-C}}\mathbf{-}{\mathbf{3}}^{\text{'}}$

The complementary antisense DNA strand is,

${\mathbf{3}}^{\mathbf{\text{'}}}\mathbf{\text{-A-G-G-}}{\mathbf{5}}^{\mathbf{\text{'}}}$

Step 5: Explanation for (d)

The mRNA molecules are made by transcribing the antisense strand of the DNA molecules.

The mRNA strand is,

$5^{\text{'}}\text{-C-A-U-}{3}^{\text{'}}$

The complementary antisense DNA strand is,

${\mathbf{3}}^{\mathbf{\text{'}}}\mathbf{\text{-G-T-A-}}{\mathbf{5}}^{\mathbf{\text{'}}}$