A protein-encoding region of a gene has the following DNA...

A protein-encoding region of a gene has the following DNA sequence: T T T CA T CA G G A T GA CA Determine how each of the following mutations alters the amino acid sequence: a. substitution of an A for the T in the first position b. substitution of a G for the $C$ in the 17 th position c. insertion of a T between the fourth and fifth DNA bases d. insertion of a GTA between the 12 th and 13th DNA bases e. deletion of the first DNA nucleotide

A protein-encoding region of a gene has the following DNA sequence:
T T T CA T CA G G A T GA CA

Determine how each of the following mutations alters the amino acid sequence:
a. substitution of an A for the T in the first position
b. substitution of a G for the $C$ in the 17 th position
c. insertion of a T between the fourth and fifth DNA bases
d. insertion of a GTA between the 12 th and 13th DNA bases
e. deletion of the first DNA nucleotide

Key Concepts

Deletion Mutation

A deletion mutation is the loss of one or more nucleotides from the DNA sequence. Like insertions, if the deletion is not in multiples of three, it causes a frameshift mutation, which can drastically alter the downstream codon reading frame and thereby impair the final protein product.

Insertion Mutation

An insertion mutation involves the addition of one or more nucleotides into the DNA sequence. Depending on the number of inserted bases, this mutation may or may not disrupt the reading frame. If the inserted bases are not in multiples of three, the reading frame shifts, potentially altering the entire amino acid sequence from the point of insertion onward.

Frameshift Mutation

Frameshift mutations occur when nucleotides are inserted or deleted from the DNA sequence in numbers not divisible by three. Such mutations shift the reading frame, altering every codon downstream, and often result in a completely different translation, frequently leading to nonfunctional proteins.

Point Mutation

A point mutation is a change in a single nucleotide base, such as a substitution. This type of mutation can result in various effects on the amino acid sequence, ranging from no change (silent mutation) to the replacement of one amino acid with another (missense mutation) or even the creation of a stop codon (nonsense mutation).

Genetic Code and Codon Translation

This concept refers to the process by which the nucleotide sequence in DNA is transcribed into mRNA and then translated into proteins via codons—groups of three nucleotides that specify particular amino acids. Understanding this process is crucial because any mutation in the DNA sequence can alter these codons, potentially affecting the amino acid sequence of the protein produced.

Transcript

00:02 Hi, today's little video is going to consider the idea of mutations.

00:11 What effects can a mutation have on a sequence of amino acids? a mutation is just a change in the dna code.

00:22 And obviously the dna code tells the cell to build proteins.

00:26 So any change in the code has the potential to affect the proteins that the cell builds, causing them to not build a protein or to build a wrong protein or potentially to build a better protein.

00:41 So we're given a sequence of dna, 17 bases.

00:47 We're told that this sequence codes for a series of amino acids.

00:52 So the first thing that we have to do, the first thing that we have to do is we have to know what this sequence yields in terms of an amino acid.

01:03 Sequence.

01:05 So we have to kind of assume that we're going through the process of transcription and converting this dna sequence into a messenger rna sequence.

01:17 And so the t, the thymine, and the dna would code for adenine in the rna.

01:29 So we would have the first codon would be a .a.

01:35 So right here is our first codon.

01:40 Let me pause and write just what that is.

01:47 So all we need to do is just go down the list here and convert each set of three dna bases into the corresponding rna bases.

02:01 So cytosine -adamine thymine is going to become guanine -euricil adenine.

02:11 And go down, we'll do this for each one.

02:14 Let me save some time and do that.

02:20 So once we know what our rna codons are, we can look at the chart in the book until the amino acid that will be coded for by each of these codons.

02:33 And so we know that aaa codes for the amino acid lysine.

02:42 So the very first amino acid in this sequence is lysine.

02:49 We know that g -u -a is going to give us valine.

02:57 That g -u -c is also going to give us valine.

03:01 Just abbreviating, you can find all this in the book if you don't already know it.

03:07 C -u -a is going to give us lucine, and c -u -g is going to also give us lusine.

03:16 And now we only have two bases left.

03:20 That's not a complete codon, so we can't tell for sure what amino acid that will be.

03:26 So let's not worry about that...