September Admission 2019/2020 into Accra Institute of Techonology, Ghana - Undergraduate Programs 6

what do you understand by the word mutation?

what do you understand by the word mutation?

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Answers (4)

isaaq
1 month ago
genes, called alleles. These small differences in DNA sequence make every individual unique. They account for the variation we see in human hair color, skin color, height, shape, behavior, and susceptibility to disease. Individuals in other species vary too, in both physical appearance and behavior.

Genetic variation is useful because it helps populations change over time. Variations that help an organism survive and reproduce are passed on to the next generation. Variations that hinder survival and reproduction are eliminated from the population. This process of natural selection can lead to significant changes in the appearance, behavior, or physiology of individuals in a population, in just a few generations.

Once new alleles arise, meiosis and s*xual reproduction combine different alleles in new ways to increase genetic variation.

alleles
Mutation vs. variation
It's useful to think of mutation as a process that creates genetic variation. We often refer to a mutation as a thing—the genetic variation itself. This approach can be useful when it comes to a gene associated with a disease: the disease allele carries a mutation, a DNA change that compromises the protein's function. However, this approach gives mutation a bad name.

It’s important to remember that losing the function of a gene doesn’t always affect health. For example, most mammals have hundreds of genes that code for olfactory receptors, proteins that help us smell. Losing one of these genes probably doesn’t make all that much difference.

In contrast to variations that cause disease, there are many more examples of variations that are neither good nor bad, but just different—like blood types and eye color. Just like with disease alleles, the process of mutation creates these more neutral variations. But with neutral variations, it can be impossible to tell which allele is the "normal" one that existed first and which is the "mutant"—and the distinction is often meaningless.

alleles
Proteins and switches
Mutation creates variations in protein-coding portions of genes that can affect the protein itself. But even more often, it creates variations in the "switches" that control when and where a protein is active and how much protein is made.

Lactase is an enzyme that helps infants break down lactose, a sugar in milk. Normally the gene that codes for lactase is active in babies and then turned off at about age four. When people who don't make lactase consume milk, they experience gas, nausea, and discomfort. But some people have a variation in a genetic switch that keeps the lactase gene active. This variation is called "lactase persistence," and people who have it can keep milk in their diets even as adults.

switches
Other drivers of mutation: Environmental agents
Radiation, chemicals, byproducts of cellular metabolism, free radicals, ultraviolet rays from.
Other drivers of mutation: Environmental agents
Radiation, chemicals, byproducts of cellular metabolism, free radicals, ultraviolet rays from the sun—these agents damage thousands of nucleotides in each of our cells every day. They affect the nucleotides themselves: converting one base to another, knocking a base off its backbone, or even causing a break in the DNA strand.

agents
DNA Repair
Most of the time, mutation is reversed. DNA repair machines are constantly at work in our cells, fixing mismatched nucleotides and splicing broken DNA strands back together. Yet some DNA changes remain. If a cell accumulates too many changes—if its DNA is so damaged that repair machinery cannot fix it—it either stops dividing or it self-destructs. If any of these processes go wrong, the cell could become cancerous.

When we put on sun screen, we are protecting ourselves against mutation in somatic cells—the cells that make up the body and are not involved in reproduction.​ Only when DNA changes are carried in egg and man-fluid cells are they passed to the next generation. Believe it or not, a certain amount of sloppiness is built into the system. Without mutation there would be no variation, and without variation there would be no evolution.
Gaby
1 month ago
A Mutation occurs when a DNA gene is damaged or changed in such a way as to alter the genetic message carried by that gene.
A Mutagen is an agent of substance that can bring about a permanent alteration to the physical composition of a DNA gene such that the genetic message is changed.
What is a gene mutation
and how do mutations
occur?
A gene mutation is a permanent alteration in
the DNA sequence that makes up a gene, such
that the sequence differs from what is found
in most people. Mutations range in size; they
can affect anywhere from a single DNA
building block (base pair) to a large segment
of a chromosome that includes multiple genes.
Gene mutations can be classified in two major
ways:
Hereditary mutations are inherited from a
parent and are present throughout a
person’s life in virtually every cell in the
body. These mutations are also called
germline mutations because they are
present in the parent’s egg or man-fluid cells,
which are also called germ cells. When an
egg and a man-fluid cell unite, the resulting
fertilized egg cell receives DNA from both
parents. If this DNA has a mutation, the
child that grows from the fertilized egg will
have the mutation in each of his or her
cells.
Acquired (or somatic) mutations occur at
some time during a person’s life and are
present only in certain cells, not in every
cell in the body. These changes can be
caused by environmental factors such as
ultraviolet radiation from the sun, or can
occur if an error is made as DNA copies
itself during cell division. Acquired
mutations in somatic cells (cells other than
man-fluid and egg cells) cannot be passed to
the next generation.
Genetic changes that are described as de
novo (new) mutations can be either hereditary
or somatic. In some cases, the mutation
occurs in a person’s egg or man-fluid cell but is
not present in any of the person’s other cells.
In other cases, the mutation occurs in the
fertilized egg shortly after the egg and man-fluid
cells unite. (It is often impossible to tell
exactly when a de novo mutation happened.)
As the fertilized egg divides, each resulting
cell in the growing embryo will have the
mutation. De novo mutations may explain
genetic disorders in which an affected child
has a mutation in every cell in the body but
the parents do not, and there is no family
history of the disorder.
Somatic mutations that happen in a single cell
early in embryonic development can lead to a
situation called mosaicism. These genetic
changes are not present in a parent’s egg or
man-fluid cells, or in the fertilized egg, but
happen a bit later when the embryo includes
several cells. As all the cells divide during
growth and development, cells that arise from
the cell with the altered gene will have the
mutation, while other cells will not. Depending
on the mutation and how many cells are
affected, mosaicism may or may not cause
health problems.
Most disease-causing gene mutations are
uncommon in the general population. However,
other genetic changes occur more frequently.
Genetic alterations that occur in more than 1
percent of the population are called
polymorphisms. They are common enough to
be considered a normal variation in the DNA.
Polymorphisms are responsible for many of
the normal differences between people such
as eye color, hair color, and blood type.
Although many polymorphisms have no
negative effects on a person’s health, some of
these variations may influence the risk of
developing certain disorders.
mizta smart
1 month ago
A Mutation occurs
when a DNA gene is damaged or
changed in such a way as to alter the
genetic message carried by that gene. A
Mutagen is an agent of substance that
can bring about a permanent alteration
to the physical composition of a DNA
gene such that the genetic message is
changed.
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