MUTATIONS & GENE EDITING
Gene mutations → structural changes or alterations in the DNA sequence of an
organism, and play a role in shaping human health
EX: sickle cell anaemia: genetic disorder is caused by a specific mutation in the
haemoglobin beta gene (HBB). HBB is responsible for production of haemoglobin,
the oxygen-carrying protein in red blood cells. A single alteration in the genetic
sequence leads to the production of abnormal haemoglobin.
The consequences of this mutation are profound. Abnormal haemoglobin molecules
can polymerise under low-oxygen conditions causing the red blood cells to adopt a
sickle shape. These deformed cells are less flexible and prone to clumping,
obstructing blood vessels and impeding the normal flow of oxygen. This cascade of
events gives rise to the various health complications associated with sickle cell
anaemia.
Interestingly, the same mutation that causes sickle cell anaemia also provides a
unique advantage: protection against malaria. In regions where malaria is prevalent,
individuals with the sickle cell trait, carrying at least one copy of the mutated HBB
gene, are less susceptible to the disease. The altered shape of their red blood cells
hinders the ability of the malaria parasite to infect and reproduce within them,
reducing the severity of malaria symptoms and providing a survival advantage.
GENE MUTATIONS
Mutations in DNA can arise from various organisms:
- Substitution
- Insertion
- Deletion
↪ structural changes to the gene
1) Substitutions
Base substitution mutations = single-nucleotide polymorphisms (SNPs) → most
common type of genetic variation. Occurs when one nucleotide is replaced by another.
This change in the DNA sequence may or may not have an effect on the structure of
the protein depending on whether the substitution is synonymous or non-synonymous.
● Synonymous substitutions: known as neutral mutations as they do not change
the amino acid sequence due to the degeneracy of the genetic code.
● Non-synonymous substitutions: change the amino acid sequence having
different effects on protein function, possibly leading to protein malfunction.
, 2) Insertions
When 1+ nucleotides are added to the DNA sequence
3) Deletions
When 1+ nucleotides are removed from the DNA sequence
Frameshift mutations: caused by either insertions or deletions as these processes alter
the reading frame of codons
↪ alteration to the aacid sequence coded for by the DNA sequence
Since the genetic code is read in codons, the addition of even one nucleotide can
disturb the grouping of codons. As a result, the mRNA transcript produced from the
mutated DNA sequence will have a different codon sequence. This could potentially
lead to changes in the resulting protein’s amino acid sequence during translation. This
shift can significantly impact the protein's structure and function.
Gene mutations → structural changes or alterations in the DNA sequence of an
organism, and play a role in shaping human health
EX: sickle cell anaemia: genetic disorder is caused by a specific mutation in the
haemoglobin beta gene (HBB). HBB is responsible for production of haemoglobin,
the oxygen-carrying protein in red blood cells. A single alteration in the genetic
sequence leads to the production of abnormal haemoglobin.
The consequences of this mutation are profound. Abnormal haemoglobin molecules
can polymerise under low-oxygen conditions causing the red blood cells to adopt a
sickle shape. These deformed cells are less flexible and prone to clumping,
obstructing blood vessels and impeding the normal flow of oxygen. This cascade of
events gives rise to the various health complications associated with sickle cell
anaemia.
Interestingly, the same mutation that causes sickle cell anaemia also provides a
unique advantage: protection against malaria. In regions where malaria is prevalent,
individuals with the sickle cell trait, carrying at least one copy of the mutated HBB
gene, are less susceptible to the disease. The altered shape of their red blood cells
hinders the ability of the malaria parasite to infect and reproduce within them,
reducing the severity of malaria symptoms and providing a survival advantage.
GENE MUTATIONS
Mutations in DNA can arise from various organisms:
- Substitution
- Insertion
- Deletion
↪ structural changes to the gene
1) Substitutions
Base substitution mutations = single-nucleotide polymorphisms (SNPs) → most
common type of genetic variation. Occurs when one nucleotide is replaced by another.
This change in the DNA sequence may or may not have an effect on the structure of
the protein depending on whether the substitution is synonymous or non-synonymous.
● Synonymous substitutions: known as neutral mutations as they do not change
the amino acid sequence due to the degeneracy of the genetic code.
● Non-synonymous substitutions: change the amino acid sequence having
different effects on protein function, possibly leading to protein malfunction.
, 2) Insertions
When 1+ nucleotides are added to the DNA sequence
3) Deletions
When 1+ nucleotides are removed from the DNA sequence
Frameshift mutations: caused by either insertions or deletions as these processes alter
the reading frame of codons
↪ alteration to the aacid sequence coded for by the DNA sequence
Since the genetic code is read in codons, the addition of even one nucleotide can
disturb the grouping of codons. As a result, the mRNA transcript produced from the
mutated DNA sequence will have a different codon sequence. This could potentially
lead to changes in the resulting protein’s amino acid sequence during translation. This
shift can significantly impact the protein's structure and function.
