The base sequences in mRNA that code for certain amino acids...

The base sequences in mRNA that code for certain amino acids are Glu: GAA, GAG Val: $\quad$ GUU, GUC, GUA, GUG Met: AUG Trp: UGG Phe: UUU, UUC Asp: GAU, GAC These sequences are complementary to the sequences in DNA. a. Give the corresponding sequences in DNA for the amino acids listed above. b. Give a DNA sequence that would code for the peptide trp-glu-phe-met. c. How many different DNA sequences can code for the tetrapeptide in part b? d. What is the peptide that is produced from the DNA sequence T-A-C-C-T-G-A-A-G? e. What other DNA sequences would yield the same tripeptide as in part d?

The base sequences in mRNA that code for certain amino acids are
Glu: GAA, GAG Val: $\quad$ GUU, GUC, GUA, GUG Met: AUG Trp: UGG Phe: UUU, UUC Asp: GAU, GAC
These sequences are complementary to the sequences in DNA.
a. Give the corresponding sequences in DNA for the amino acids listed above.
b. Give a DNA sequence that would code for the peptide trp-glu-phe-met.
c. How many different DNA sequences can code for the tetrapeptide in part b?
d. What is the peptide that is produced from the DNA sequence T-A-C-C-T-G-A-A-G?
e. What other DNA sequences would yield the same tripeptide as in part d?

Key Concepts

Transcription and Translation

Transcription is the process by which a DNA sequence is converted into an mRNA sequence, relying on complementary base pairing. Translation is the subsequent process where the mRNA is read by a ribosome in sets of three nucleotides (codons) to assemble a corresponding chain of amino acids, forming a peptide. Both processes are fundamental to gene expression and protein synthesis.

Degeneracy of the Genetic Code

The genetic code is degenerate, meaning that most amino acids are encoded by more than one codon. This redundancy allows for variations in the nucleotide sequence that still result in the same amino acid being incorporated into a protein. It is significant in understanding how different DNA sequences can code for the same peptide.

DNA and RNA Sequence Differences

A key difference between DNA and RNA lies in their nucleotide composition and structure. DNA contains the sugar deoxyribose and the base thymine, while RNA contains ribose and the base uracil. Recognizing these differences is critical when converting sequences between DNA and mRNA and understanding how genetic information is maintained and expressed.

Complementary Base Pairing

This concept refers to the specific pairing between nucleotide bases in DNA and RNA. In DNA, adenine (A) pairs with thymine (T) and guanine (G) pairs with cytosine (C), while in RNA, uracil (U) replaces thymine and pairs with adenine. Understanding this pairing is essential for converting sequences between DNA and mRNA, as well as for understanding the transcription process.

Coding Sequences (Codons)

Codons are triplets of nucleotides in mRNA that specify which amino acid will be added next during protein synthesis. Each codon corresponds to a particular amino acid or a stop signal. This concept is central to the translation process where the genetic code is read in sets of three to construct proteins.

Transcript

00:01 In this question, we are given some codons that code for certain amino acids in mrna, and we are asked to give the corresponding sequences in dna for part a.

00:09 So these are all the mrna sequences, and we're going to draw the, or write down the corresponding dna pairs.

00:17 So the only difference between rna and dna is that rna uses u instead of t.

00:22 So u, oops, why are my pen marking? you, there we go, u becomes t in dna.

00:34 So here we have g -a -a, so g pairs with c and a pairs with t, so c -t -t -t, and then g -a -g becomes c -t -c.

00:45 Now for vailene here, g -u -u, so this becomes c, and then u is base, is the same thing as t, well, not the same thing, but the replacement for t, so it base pairs with a.

01:00 So c -a -a is our base pair here.

01:02 And then we have c -a -g, c -a -u, and c -a -c.

01:12 For methyanine, we have t -a -c, and then we have a -c, and then we have a -c, and a -a -a -a -a -g, and then down here we have c -t -t -t -t, a and c -t -g.

01:41 So those are all of our dna corresponding sequences.

01:46 And then part b asked for a dna sequence that would code for the peptide, for this peptide here.

01:53 So the first one would be a, c, c, and then the next one, if we look for this, that's right here.

02:03 There's two options here, so we'll just pick one.

02:05 So let's say c -t -t -t.

02:09 And then next we have, again, two options.

02:11 So let's say a -a -a.

02:14 And then last one, there's only one option.

02:16 So t -a -c.

02:17 So there is our sequence for that peptide.

02:21 And then part c asked how many different dna sequences could code for that peptide...