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: 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 peptide 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: 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 peptide 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

Genetic Code

The genetic code is the set of rules by which information encoded within messenger RNA (mRNA) sequences is translated into proteins by living cells. It defines the correspondence between triplet nucleotide sequences, known as codons, and specific amino acids. This concept is central to understanding how sequences in mRNA (and their corresponding DNA sequences) determine which amino acids are incorporated into a peptide during translation.

Complementary Base Pairing

Complementary base pairing refers to the specific pairing of nucleotides between two strands of nucleic acids. In DNA, adenine (A) pairs with thymine (T) and cytosine (C) pairs with guanine (G); while in RNA, adenine pairs with uracil (U) instead of thymine. This principle is crucial for converting mRNA sequences into DNA sequences and vice versa, as the sequences are complementary to each other.

Codon Degeneracy

Codon degeneracy is the phenomenon where multiple codons can encode for the same amino acid. This intrinsic redundancy in the genetic code means that a single amino acid might be specified by several different nucleotide triplets. Understanding codon degeneracy is important when determining how many unique DNA sequences can code for a given peptide, as different codon choices can yield the same amino acid sequence.

DNA Transcription and Translation

DNA transcription and translation are the two key processes in gene expression. Transcription is the process through which a segment of DNA is used as a template to synthesize mRNA, while translation is the subsequent process where ribosomes read the mRNA codons to assemble the corresponding amino acids into a peptide chain. This concept is essential for understanding how nucleotide sequences are converted into functional proteins.

Transcript

00:01 This problem gives us a few different amino acids here and tells us what the mrna codes are for them.

00:11 And then the part a asks us to give the corresponding sequences in dna for each of the ones that they give us.

00:17 So remember that g pairs with c and then a pairs with t.

00:24 And you'll notice there are no t's in these, but there are u's.

00:27 And so in dna, we use thymine, but in rna, thymine is replaced with uracil, which is u.

00:34 So a also pairs with u.

00:37 So starting with the first one here, g -a, so g -a is c, and then a turns into t in dna, so c -t -t -t.

00:49 And then the second one, the second version of this amino acid is g -a -g, so that would be c -t -c -t -s.

00:59 For valine, which is next, we have g -u -u -u, so g turns into c, and then u turns into a, so c -a, g -u -c becomes c -a -g with its pair, and then g -u -a, g becomes c, u -a, g becomes c, u becomes a, a becomes t in dna.

01:22 And then g -u -g, we have c -a -c is our complement.

01:27 For methyanine, which is next, we have, we a u -g so a becomes t in dna u becomes a and g becomes c for triptophan u g -g -g so u becomes a g becomes c so ac c for phenylalanine which is next u -u -u -u -u becomes a -a -u -c.

01:51 We have that a -a from the u's and then c becomes g.

01:55 For g -a -u -g -b -c -b -c, a becomes t, and u becomes a, and then g -a -c -g becomes c, g -t -g.

02:11 And then part b asks us to give a dna sequence that would code for this peptide here.

02:21 So first we have a tryptophan.

02:24 So that is right here.

02:26 We just coded that for acc.

02:29 And then let's write it like this.

02:34 A.

02:36 C.

02:37 C.

02:37 And then for the next one, we coded two different options here.

02:42 So each one will work.