Question

a dna strand has the following sequence of nucleotides:
t－a－c－g－c－a－a－t－g－c－c－a－a－t－t
a. what will the mrna sequence be?
b. how many codons does the mrna have?
c. using the chart from the on your own question 6.13, how many amino acids will the mrna code for and what are they?

Explanation:

Step1: Transcribe DNA to mRNA

In transcription, DNA's T pairs with A, A pairs with U, C pairs with G, G pairs with C.
DNA: $T-A-C-G-C-A-A-T-G-C-C-A-A-T-T$
mRNA: $A-U-G-C-G-U-U-A-C-G-G-U-U-A-A$

Step2: Count mRNA codons

Codons are 3-nucleotide groups. Count total mRNA nucleotides: 15.
Number of codons = $\frac{15}{3} = 5$

Step3: Map codons to amino acids

Use standard genetic code:

1. $AUG$ = Methionine (start codon)
2. $CGU$ = Arginine
3. $UAC$ = Tyrosine
4. $GGU$ = Glycine
5. $UAA$ = Stop codon (no amino acid)

Count valid amino acids: 4

Answer:

a. $A-U-G-C-G-U-U-A-C-G-G-U-U-A-A$
b. 5
c. 4 amino acids: Methionine, Arginine, Tyrosine, Glycine