mRNA sequence coding question help needed

Chemistry
Tutor: None Selected Time limit: 1 Day

Oct 22nd, 2015

Thank you for the opportunity to help you with your question!

Hi, what were the instructions for this chart, or did you just need the chart explained? This chart is what you use in order to find what nucleotide base sequences correspond to which peptide. For example, a nucleotide base sequence is made of 3 bases such as AUU. This is called a codon. You use the chart you have in order to find what peptide/amino acid AUU corresponds to. 

So lets continue with the AUU example. The first base of this RNA codon is A. Now you look at the left hand side of the chart and find where A is. A is in first column in the 3rd box. Now you look at the second base in the sequence which is U. For the second sequence you look at the top of the chart and find U. You can see that it's the first letter on the top of the chart. So now you found which box corresponds to the first 2 bases in the sequence AU. It's the 3rd box in the far left column. 

The last step is to look at the last base in the sequence which is U again. Now that you know what box you are in you look and find which one ends in U. You should be able to see that the sequence AUU corresponds to the amino acid peptide Isoleucine. So ultimately, this chart is showing you what kind of peptides the base sequence encodes for. 

If you have any additional questions just let me know and I'll be happy to help you!
Oct 22nd, 2015

What is the mRNA sequence for the following segment of DNA?
--AAATGTGTGCTAACA--
Based upon the mRNA sequence, what is the peptide sequence?

Oct 22nd, 2015

I forgot to mention what the start and stop words mean. The sequence AUG sequence is called the start codon because that is what signals the start of translation into a protein. Met means the amino acid methionine. There is only one start codon but there are 3 stop codons. These can be either UAA, UAG or UGA. These signal translation when to terminate or stop. 

Oct 22nd, 2015

Can you help me answer the questions? 

Oct 22nd, 2015

1. So the first step is to convert the DNA sequence into mRNA. In the DNA sequence A will pair with U, T will pair with A, and G and C will pair with each other. Basically, 

A and U

T and A 

G and C

C and G

T is replaced by U in the mRNA sequence and that is why A pairs with U and not T. So if you match these up the correct mRNA sequence will be:

UUUACACACGAUUGU 

2. Now just split this up into segments of 3 and use the chart to figure out which segment corresponds to which peptide. Split up it's UUU ACA CAC GAU UGU

Now just use the chart starting with the first letter in the first segment and work your way through. 

UUU = Phenylalanine 

ACA = Threonine 

CAC = Histidine 

GAU = Aspartic Acid

UGU = Cysteine 

Oct 22nd, 2015

Are you understanding it a little better?

Oct 22nd, 2015

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