# If the sequence of bases in DNA is TAC, then the sequence of bases in mRNA will be?

Apr 13, 2018

$A U G$

#### Explanation:

On DNA and RNA, the bases that attach to each other are:

$C \leftrightarrow G$

$A \leftrightarrow T$ (DNA) or $U$ (RNA)

So whatever you see in the one strand, you'll just switch to the other letter in the pair for the other strand.

Now remember, since we are changing to RNA, we will use $U$ and not $T$. So the strand $T A C$ will change to:

$T \rightarrow A$
$A \rightarrow U$
$C \rightarrow G$

$A U G$.

Apr 14, 2018

$\text{AUG}$

#### Explanation:

Well, the sequence here is $\text{TAC}$ in the $\text{DNA}$.

Remember that adenine $\left(\text{A}\right)$ only bonds to thymine $\left(\text{T}\right)$ with two hydrogen bonds, while cytosine $\left(\text{C}\right)$ only bonds with guanine $\left(\text{G}\right)$. Also note that uracil $\left(\text{U}\right)$ is substituted for thymine in $\text{RNA}$.

So, the corresponding sequence in $\text{RNA}$ will be,

$\text{ATG}$

Now, substitute $\text{U}$ for $\text{T}$.

$\implies \text{AUG}$

Apr 14, 2018

It depends if the sequence is top strand or bottom strand. See below.

If assume this DNA sequence is the top strand, the mRNA will be UAC.

#### Explanation:

Usually when a sequence is written, it is written as the top strand.

5$TAC3$

And that means the bottom strand is 3$ATG5$

So the DNA would look like:

5$TAC3$ - top strand
3$ATG5$ - bottom strand

mRNA is made off the bottom strand, and makes a complement of the bottom strand (which means the mRNA is the same sequence as the top strand, but in the form of RNA).

So, when polymerase comes along and makes RNA (lower case), it uses the bottom strand.

5$u a c 3$ NEW mRNA
3 ATG5$bottom template strand of DNA. so the resulting mRNA will be UAC. If we assume TAC is the bottom strand, all DNA is written 5$to 3$, so it should be 3$CAT5` as the template.
That means the mRNA made from this would be:
GUA