DNA is what comprises our chromosomes. But let's talk about what happens when there's an error in DNA sequencing. An error in our DNA is called a "mutation." Some mutations can happen accidentally; some can be triggered by things in the environment, an ultraviolet radiation, toxins, and x-rays, for example. For whatever reason, something happens to the sequence in nitrogen bases in the DNA and those mutations can either be helpful, harmful, or not really matter at all. But before we talk more about mutations, let's look at DNA for just a second. 00:38: Remember that DNA is made up of hundreds of thousands of nitrogen bases and they form specific pairs. This is called the base pair rule. In a DNA molecule, adenine always pairs with thymine, that is A pairs with T. And cytosine always pairs with guanine, or C pairs with G. Also in a DNA molecule, every three of these bases represents what we call a "codon", and that codon codes for a specific amino acid. So your DNA codes for your genetic characteristics, and they also code for specific proteins being manufactured in your cells. If any of these are changed for any reason, the code changes. 01:27: So let's make believe that this is a specific codon that codes for amino acid. If a letter is lost, replaced, or added, that codon is altered. And that's basically what a mutation is. And again, it can be accidental, or it can be the result of toxins and mutagens in your environment like ultraviolet radiation. Let's look for a minute at the three most common kinds of mutations. One common mutation is called "deletion". Instead of having six nitrogen bases, one is lost. Now the whole sequence is thrown off, and when these code for amino acids, instead of saying ATC it will now say ATG. 02:11: Another thing that can happen is that a nitrogen base can be inserted. So originally, there was ATC, now though through a mutation, instead of the C there is another T. So the code has been changed by inserting a different nitrogen base. Another thing we can do is invert. So the original sequence was ATC, we could flip this around, it could become CTA. And again, we've changed the code. So remember, a mutation is a change in the genetic sequence and the sequence of nitrogen bases in DNA. It can happen accidentally, environmentally, and the change can either be helpful, harmful, or not really matter at all.
Close
Question 1
A _______ is a change in the DNA sequence.
Responses
A mutationmutation
B displacementdisplacement
Question 2
Each codon of a DNA molecule code is for a specific ________________.
Responses
A phenotypephenotype
B amino acidamino acid
Question 3
An original DNA sequence is: CGA TGG CCA TTA. The mutated sequence is: CGA GG CCA TTA This mutation is called a ________________.
Responses
A deletiondeletion
B replacementreplacement
C hybrid
B replacement
please answer all 3 questions
Question 1: A mutation is a change in the DNA sequence.
Question 2: Each codon of a DNA molecule codes for a specific amino acid.
Question 3: An original DNA sequence is: CGA TGG CCA TTA. The mutated sequence CGA GG CCA TTA is called a deletion.