If a change does happen, we call it a mutation. The rate of change is increased by radiation from the sun’s or other sources’ atomic radiation.
Discuss why most mutations never influence the genome of the population.
Bryony's Response:
DNA replication is very vital to an organism’s survival as it needs to happen for cells to divide. DNA replication is a very complicated process but is also very accurate but sometimes mutations do happen. There are many different types of mutations and many will affect people differently and mutations can be caused by environmental factures such as radiation. But despite all this most mutations do not have an effect on the genome of the human population.
DNA replication occurs when new cells are created. Before a
cell can divide into daughter cells the DNA must be replicated to produce the new
chromosomes for the new cells to carry. DNA replication occurs when the body
needs to make new cells. DNA replication starts when a cell is preparing to
divide. An enzyme called Helicase splits the DNA double helix down the middle
separating the two strands of DNA. As the strands unwind an enzyme called
gyrase prevents the strands from getting tangled by making temporary nicks in
the strands that will be sealed up later. When the two strands are separated
several small proteins called single stand binding proteins temporarily bind
each side and keep them from re-joining with each other. As the strands unzip
the bases become exposed and an enzyme called DNA polymerase III goes down the
DNA strands and add new nucleotides to each strand. The nucleotides pair with
the complementary nucleotides on the existing strand. But when the double helix
is split there is a leading strand and a lagging strand. Because DNA polymerase
must move in the 5' to 3' direction on the DNA strand when the enzyme is on the
lagging strand the enzyme must move away from the replication fork. The
replication fork is the junction point where the strands are being split. If
the enzyme moves away from the fork while the fork is uncovering new DNA some
DNA will not be replicated. So the lagging strand needs to be replicated in
small segments. These fragments are then stitched together by DNA ligase and
this creates a full strand of DNA. This shows that DNA replication is a very
complicated process that is necessary for cells to divide.
Although DNA replication is extremely accurate sometimes
things go wrong and mutations can occur. A mutation is a permanent change in
the DNA sequence that makes up a gene. Mutations are caused by DNA replication
going wrong. Every time a human cell
divides and its DNA replicates it has to copy and transmit the exact same copy
of three billion nucleotides to it daughter cells. Like everything else in the world
DNA replication is not always perfect. Sometimes mistakes happen with the
polymerase enzymes and they insert the wrong nucleotide or to many or two few
nucleotides into a sequence. Fortunately many of these mistakes are fixed by
various DNA repair processes and DNA repair enzymes. But some replication
errors make it past the repairing enzymes becoming permanent mutations.
Mutations can also be caused by environmental factures such as nuclear
radiation and ultraviolet light from the sun. Ultraviolet light, nuclear
radiation and certain chemicals can damage DNA by altering a nucleotides base
so that it seems like another base. So when the DNA replicates the altered base
will pair with an incorrect base and cause a mutation. For example an altered
guanine base could get pair with a thymine base. This would cause a permanent
mutation in the DNA sequence. Environmental
factures especially nuclear radiation can also break the phosphate back bone of
DNA that carries a gene. This creates a mutated form of the gene that may
produce different proteins. Also cells that have broken DNA will try to fix the
broken ends of DNA by joining the loose ends to other pieces of DNA within the
cell. This creates a mutation called translocation. If the breakage point is
within or near a gene the gene’s function may be altered. This shows how
mutations occur and that although they can happen regularly they are not all
permanent.
There are many types of mutations. Mutations can range in
size from a single DNA base to a large part of the chromosome. There are three
types of mutations germline mutations, de novo mutations and somatic mutations.
Germline mutations are present in gametes. This type of mutation is present
throughout a person’s life and is in virtually every cell in their body. This
type of mutation can be passed down to the next generation and is sometimes
called hereditary mutations. De novo mutations only occur in an egg or sperm
cell or during fertilization. This mutation well be present throughout the
person’s life in very one of their cells but there will be no family history of
this mutation. Somatic mutations occur in individual cells at some time during
a person’s life. But since these mutations occur in somatic cells which are
cells that are not gametes they will not be passed on to other generations.
These types of mutations will affect people differently for example a somatic
mutation will not be present throughout all of someone’s life unlike a de novo
mutation which will be. De novo mutations can be things like mental disorders
and birth defects such as heart problems. While a somatic mutation would more
likely cause cancer or other diseases. This shows that different types of
mutations affect people in different ways. Therefore each mutation can be different
and have different effects on someone’s life. But do many mutations affect the
overall human population genome.
Most mutations do not affect the genome of the human
population because many mutations occur in somatic cells so they don’t get
passed on, many mutations occur in noncoding DNA, there are so many humans in
the world that one mutation will not really affect the overall genome of the
population and if a mutation is extremely bad the person with it will not
survive . Mutations that happen in somatic cells will not be passed down to the
next generation because they do not occur in gametes so not many humans will
carry this mutation because it cannot be inherited. For example a mutation that
can be inherited like being left handed will spread throughout the human
population more than a mutation that cannot be inherited. Another reason is
because about 95% of human DNA is noncoding DNA meaning that it does not code
for proteins that are not expressed in the organism’s phenotype. Because a lot
of our DNA is noncoding the chances are that mutations will not happen in the
coding DNA so they will not have any effect on the person’s genome or the
populations. Another reason is because there are simply so many people on the
planet that if a mutation occurred in one or two peoples genes it will not make
a big difference in the genome of the population because there are millions of
people without this mutation and the chances that they will breed with someone
with the same mutation is very slim. For example if someone with a mutation
breed with someone without the mutation the children may not carry the mutation
and the mutation would have to be in the parents gametes to be passed down to
the children anyway so the chances of all this happening are very slim. Lastly
if a mutation is extremely bad the person carrying it would not be able to
survive or would not be able to produce children so the mutation would no get
passed on anyway. This shows that many mutations don’t get passed down to other
generations that most mutations occur in noncoding DNA and if mutation is
really really bad it will not get passed down anyway. Therefore most mutations
do not affect the genome of the human population.
Although some mutations to spread through the human
population. Mutations that spread through the population are generally
mutations in gametes because they can be passed down to other generations. An
example of this is not having a hitch hiker’s thumb or being left handed. Both
of these mutations can be inherited and have passed through a lot of the
population because it’s not extremely odd to find someone who has a straight
thumb or who is left handed. So some mutations can affect the human population’s
genome. This shows that some mutations can affect the population’s genome but
when you think of all the other mutations that will occur in peoples DNA
everyday it becomes clear that most mutations must not affect the genome of all
the population or the human race would be every mutated and constantly changing
characteristic as new mutations occurred.
To conclude DNA replication is a very accurate
process but nothing is perfect and mutations do happen sometimes. Mutations can
be caused by environmental factures such as radiation there are many different
types of mutation and each type will affect people differently. Most mutation does
not affect the genome of the human population because they occur in noncoding
DNA and the chances of the being passed on are very thin. I believe that my
information is reliable because a lot of it doubled up on different websites
and this lead me to believe that the information was correct and the
information seemed to be believable. Therefore most mutations do not affect the
genome of the human population.
