Download NAME: NWAIWU ROSEMARY DEPT: BIOCHEMISTRY COURSE

NAME: NWAIWU ROSEMARY
DEPT: BIOCHEMISTRY
COURSE: BIO 201
MUTATION: A CURSE OR A BLESSING.
MUTATION: A mutation is a permanent change to DNA. These changes occur when DNA
repair mechanisms fail to repair damage, when DNA replicates incorrectly, or form the deletion
or insertion of DNA segments. Some mutations occur within the lifetime of a single organism.
These somatic mutations involve direct damage to an organism’s DNA from an environmental
source. For example, damage from ultraviolet rays damages DNA in a way that gives rise to
cancerous cells.
Other mutations are heritable and pass from one generation to another. One particular
heritable mutation causes a deletion of 32 base pairs affecting the human CCR5 protein.
Research suggests that people with this gene possess immunity to bubonic plague or small pox,
a very beneficial mutation to people at various periods in human history. Because of higher
survival rates of people with the CCR5 mutation, the mutation persists into the present day. For
modern humans, a CCR5 mutation means resistance to HIV.
Mistakes occur constantly during the replication, translation and transcription of DNA.
Fortunately, nearly 98 percent of human DNA is noncoding DNA with no apparent functions and
mutations in noncoding DNA have no effect.
TYPES OF MUTATION
MISSENSE MUTATION- This type of mutation is a change in one DNA base pair that results in
the substitution of one amino acid for another in the protein made by a gene. (i.e. a change in
a single “chemical letter” such as switching an A to a G) such a substitution could change a
codon to one that encodes a different amino acid and cause a small change in the protein
produced. For example, sickle cell anemia is caused by a substitution in the beta-haemoglobin
gene, which alters a single amino acid in the protein produced.
NONSENSE MUTATION- A nonsense mutation is also a change in one DNA base pair. Instead
of substituting one amino acid for another, however, the altered DNA sequence prematurely
signals the cell to stop building a protein. This type of mutation results in a shortened protein
that may function improperly or not at all.
INSERTION- An insertion changes the number of DNA bases in a gene by adding a piece of
DNA. As a result, the protein made by the gene may not function properly.
DELETION- A deletion changes the number of DNA bases by removing a piece of DNA. Small
deletions may remove one or a few base pairs with a gene, while larger deletions can remove
an entire gene or several neighboring genes. The deleted DNA may alter the function of the
resulting protein(s)
DUPLICATION- A duplication consists of a piece of DNA that is abnormally copied one or
more times. This type of mutation may alter the function of the resulting protein.
FRAMESHIFT MUTATION- This type of mutation occurs when the addition or loss of DNA
bases changes a gene’s reading frame. A reading frame consists of groups of 3 bases that each
code for one amino acid. A frameshift mutation shifts the grouping of these bases and changes
that code for amino acids. The resulting protein is usually nonfunctional. Insertions, deletions,
and duplications can all be frameshift mutations.
REPEAT EXPANSION- Nucleotide repeats are short DNA sequences that are repeated a
number of times in a row. For example, a trinucleotide repeat is made up of 3-base-pair
sequences, and a tetranucleotide is made up of 4-base-pair sequences. A repeat expansion is a
mutation that increases the number of times that the short DNA sequence is repeated. This
type of mutation can cause the resulting protein to function improperly.
Mutations happen, they happen with great regularity. Almost all mutations are
neutral and whether they are helpful/harmful depends on the environment (circumstances).
Advantages of Mutation
SURVIVAL- Mutations have allowed humans to adapt to their environment. For instance, lactose
tolerance is a specific external mutation that was advantageous in societies that raised cows
and goats. Mutations have been responsible for antibiotic resistance in bacteria, sickle cell
resistance to malaria, and immunity to HIV, among others. A rare gene mutation leading to
unusual shortness of height has proven to be advantageous for a particular Ecuadorian
community, the Ecuadorian community with the rare gene mutation known as Laron syndrome
are protected against cancer and diabetes.
DIVERSITY- Originally we all had brown eyes but a genetic mutation affecting the OCA2 gene in
our chromosomes resulted in the creation of a “switch”, which literally turned off the ability to
produce brown eyes. This explains that things like hair colour, baldness, freckles, and beauty
spots are all brought about by mutations.
Disadvantages of Mutation
DISEASE- As much as mutations have helped humans, mutations are also the cause of certain
diseases. For instance, a particular mutation relatively common on the Indian subcontinent
predisposes people to heart disease, many other diseases, such as cancer, diabetes and
asthma, are linked to genetic mutations.
GENETIC DISORDER- A genetic disorder is a disease that is cause by abnormality in an
individual’s DNA. Abnormalities can range from a small mutation in a single gene to the addition
or subtraction of an entire chromosome or set of chromosomes. Non-disjunction is one of the
most common types of mutations. Down syndrome is a non-disjunction and a common genetic
disorder that has other consequences such as developmental delays.
Mutation can also be errors in all or part of a chromosome. Humans normally have 23pairs of
chromosomes, and an extra chromosome can have a tremendous negative impact. For
example, there should be two of chromosome 21, as with all other chromosomes, but if there
are three, the result is Down syndrome. People with Down syndrome have a unique physical
appearance and are developmentally disabled. Nor is an extra chromosome the only
chromosomal abnormality that causes problems: if chromosomes 9 and 22 exchange materials,
a phenomenon known as translocation, the result can be a certain type of leukemia. Down
syndrome also results from translocation.
CLASSIFICATION OF MUTATION.
1.By effect on structure
The sequence of a gene can be altered in a number of ways. Gene mutations have varying
effects on health depending on where they occur and whether they alter the function of
essential proteins.
2. by effect on fitness
3. by inheritance
4. by impact of protein synthesis.