Video Transcript
A sequence of DNA is transcribed into an RNA sequence. This RNA sequence reads five prime UACGAGAACCGA three prime. Use the codon wheel provided to determine the sequence of amino acids. Is it (A) stop, aspartate, lysine, proline? (B) Serine, glycine, glutamine, serine. (C) Histidine, glutamate, threonine, arginine. (D) Tyrosine, aspartate, glutamine, proline. Or (E) tyrosine, glutamate, asparagine, arginine.
To answer this question, let’s first review the important processes of transcription
and translation.
Genes provide the instructions for making proteins. There are two stages in the expression of a gene. The first stage is transcription, which is the process of converting a DNA sequence
into mRNA. The section of DNA is used as a template which is transcribed, or copied, into
mRNA. The mRNA produced is complementary to the DNA. However, because it is RNA, it includes uracil in the place of thymine. The mRNA produced can then leave the nucleus and travel to the ribosome, where the
next stage of protein synthesis occurs.
Translation is the process of converting an mRNA sequence into a polypeptide that can
fold into a protein. Twenty different amino acids are involved in protein synthesis, and each amino acid
is coded for by a sequence of RNA. Each amino acid is coded for by three nucleotide bases, also called a codon. For example, the DNA sequence ATG would be transcribed into AUG in mRNA. This would code for the amino acid methionine.
Now that we have reviewed the processes of transcription and translation, let’s have
another look at our question.
The RNA sequence first needs to be divided up into codons. This gives us four codons: UAC, GAG, AAC, and CGA. Next, we can use our codon wheel to determine the amino acids each codon codes
for. UAC codes for tyrosine. GAG codes for glutamate. AAC codes for asparagine. CGA codes for arginine. So the correct sequence of amino acids is shown in answer choice (E): tyrosine,
glutamate, asparagine, arginine.
