What is a Mutation?
Genetic mutations are changes/mistakes in the DNA nucleotide sequence.
They can be caused by external factors, such as ultraviolet radiation, or internal factors such as problems in DNA replication.
Mutations can be advantageous (think x-men), neutral, or negative (think cancer).
They can be caused by external factors, such as ultraviolet radiation, or internal factors such as problems in DNA replication.
Mutations can be advantageous (think x-men), neutral, or negative (think cancer).
Mutations
The nucelotide sequence is read in groups of 3. To demonstrate the various mutations, we will use this line of code as an example:
ATA CCG GAC TAC
Deletion: Genetic material or bases are removed.
Ex: If we were to remove the first base, the sequence would look like this: TAC CGG ACT AC
Insertion: Genetic material or bases are added.
Ex: If we were to add a C in the beginning: CAT ACC GGA CTA C
Base Subsitution: A single base is changed.
Ex: Changing the first A into a G: GTA CCG GAG TAC
These changes can cause different amino acids to be coded but not always because there is a lot of redundancy in amino acid coding.
ATA CCG GAC TAC
Deletion: Genetic material or bases are removed.
Ex: If we were to remove the first base, the sequence would look like this: TAC CGG ACT AC
Insertion: Genetic material or bases are added.
Ex: If we were to add a C in the beginning: CAT ACC GGA CTA C
Base Subsitution: A single base is changed.
Ex: Changing the first A into a G: GTA CCG GAG TAC
These changes can cause different amino acids to be coded but not always because there is a lot of redundancy in amino acid coding.
The Notorious Sickle Cell Anemia Example
Sickle cell anemia occurs when there is a base subsitution in the DNA that results in the changing of the 6th codon in the beta chain of hemoglobin. Usually, the DNA should be "GAG" and thus the mRNA codon is "GAG" which produces the amino acid Glutamic acid (Glu). Instead, the DNA is "GTG" so the mRNA becomes "GUG" and the amino acid changes to Valine (Val).
This change in amino acid alters the structure of hemoglobin by causing it to form fibrous strands. This causes the red blood cell to have a sickle shape instead of a round one.
Sickle cells don't effectively carry oxygen and are more easily destroyed, thus they would be considered a harmful mutation. The condition only occurs in individuals that have both alleles for it, making the condition homozygous recessive. However, if an individual lives in Africa, being heterozygous (having only one sickle cell allele) for the condition is beneficial because it causes an increased resistance to malaria.
This change in amino acid alters the structure of hemoglobin by causing it to form fibrous strands. This causes the red blood cell to have a sickle shape instead of a round one.
Sickle cells don't effectively carry oxygen and are more easily destroyed, thus they would be considered a harmful mutation. The condition only occurs in individuals that have both alleles for it, making the condition homozygous recessive. However, if an individual lives in Africa, being heterozygous (having only one sickle cell allele) for the condition is beneficial because it causes an increased resistance to malaria.