Question

1. the following question has two parts. first, answer part a. then, answer part b.

part a:
a sequence of a dna strand is shown below.
5 gcaatgacgtga 3
which mrna codon series corresponds to the dna sequence?
cgu uac ugc acu
cga auc agc uca
ccu uac ucc acu
ggu uug ugg ugu
clear all

Explanation:

Step1: Recall base - pairing rules for transcription

In transcription, DNA (template strand) is transcribed to mRNA. The base - pairing rules are: A (adenine) in DNA pairs with U (uracil) in mRNA, T (thymine) in DNA pairs with A (adenine) in mRNA, G (guanine) in DNA pairs with C (cytosine) in mRNA, and C (cytosine) in DNA pairs with G (guanine) in mRNA.

Step2: Divide the DNA sequence into triplets

The DNA sequence is \(5'\text{ GCA ATG ACG TGA }3'\).

Step3: Transcribe each triplet

• For the triplet \(GCA\):
• \(G

ightarrow C\), \(C
ightarrow G\), \(A
ightarrow U\). So it transcribes to \(CGU\).

• For the triplet \(ATG\):
• \(A

ightarrow U\), \(T
ightarrow A\), \(G
ightarrow C\). So it transcribes to \(UAC\).

• For the triplet \(ACG\):
• \(A

ightarrow U\), \(C
ightarrow G\), \(G
ightarrow C\). So it transcribes to \(UGC\).

• For the triplet \(TGA\):
• \(T

ightarrow A\), \(G
ightarrow C\), \(A
ightarrow U\). So it transcribes to \(ACU\).

Answer:

CGU UAC UGC ACU