Mutation, non-random mating, assortative mating, and natural selection can all affect allele changes in frequency in a population. Mutation is the permanent alteration of DNA sequences that can occur due to errors during DNA replication or damage. It can result in changes to gene function. Non-random mating occurs when individuals select mates non-randomly, altering gene frequencies. Assortative mating is when individuals mate with others of similar phenotypes more than expected by chance, which can increase genetic relatedness. Natural selection is the differential survival and reproduction of individuals based on phenotype, driving changes in allele frequencies over generations.

1. Factors Affecting Allele Changes in Frequency
Mutation
Non-random Mating
Assortative Mating
Natural Selection

2. MutationMutation is the permanent alteration of
the nucleotide sequence of the genome of
an organism, virus, or extrachromosomal DNA or
other genetic elements. Mutations result from
errors during DNA replication or other types of
damage to DNA, which then may undergo error-
prone repair (especially microhomology-mediated
end joining), or cause an error during other forms
of repair, or else may cause an error during
replication (translesion synthesis). Mutations may
also result from insertion ordeletion of segments
of DNA due to mobile genetic
elements. Mutations may or may not produce
discernible changes in the observable
characteristics (phenotype) of an organism.
Mutations play a part in both normal and
abnormal biological processes
including: evolution, cancer, and the development
of the immune system, including junctional
diversity.

3. Mutation can result in many different
types of change in sequences. Mutations
in genes can either have no effect, alter
the product of a gene, or prevent the gene
from functioning properly or completely.
Mutations can also occur in nongenic regions.
One study ongenetic variations between
different species of Drosophila suggests that,
if a mutation changes a protein produced by a
gene, the result is likely to be harmful, with an
estimated 70 percent of amino
acid polymorphisms that have damaging
effects, and the remainder being either
neutral or marginally beneficial. Due to the
damaging effects that mutations can have on
genes, organisms have mechanisms such as
DNA repair to prevent or correct mutations by
reverting the mutated sequence back to its
original state.

4. Non-random MatingIn order to satisfy the Hardy-Weinberg
equilibrium, individuals within a
population must mate at random.
However, in actuality, non-random
mating appears to be quite common in
most populations. Breeding territories,
courtship display or hierarchical
orders within populations are
some factors that contribute
to selective mating. When individuals
are choosy over mates, gene
frequencies are also altered. Darwin
called this phenomenon sexual
selection.

5. Assortative Mating
Assortative mating is a mating pattern
and a form of sexual selection in which individuals
with similar phenotypes mate with one another
more frequently than would be expected under a
random mating pattern. Examples of similar
phenotypes include, but are not limited to, body
size, skin coloration/pigmentation, and age.
Assortative mating, also referred to as positive
assortative mating or homogamy, may increase
genetic relatedness within the family. Assortative
mating can be contrasted with disassortative
mating (also known as negative assortative
mating or heterogamy) in which individuals with
dissimilar genotypes and/or phenotypes mate
with one another more frequently than would be
expected under random mating.

6. Disassortative mating
reduces the genetic similarities
within the family. Positive
assortative mating occurs more
frequently than negative
assortative mating. In both
cases, due to the nonrandom
mating pattern, there is a
deviation from the Hardy–
Weinberg principle (which
states that genotype
frequencies in a population will
remain constant from
generation to generation in the
absence of other evolutionary
influences).

7. Natural selection is the differential survival
and reproduction of individuals due to differences in
phenotype. It is a key mechanism of evolution, the
change in heritable traits of a population over time.
Charles Darwin popularised the term "natural
selection“ he compared it with artificial selection
(selective breeding).
Natural Selection

8. Variation exists within
all populations of organisms. This occurs
partly because random mutations arise in
the genome of an individual organism,
and offspring can inherit such mutations.
Throughout the lives of the individuals,
their genomes interact with their
environments to cause variations in traits.
(The environment of a genome includes
the molecular biology in the cell, other
cells, other individuals,
populations, species, as well as the abiotic
environment.) Individuals with certain
variants of the trait may survive and
reproduce more than individuals with
other, less successful, variants. Therefore,
the population evolves. Factors that affect
reproductive success are also important, an
issue that Darwin developed in his ideas
on sexual selection (now often included in
natural selection) and on fecundity
selection, for example.

9. Natural selection acts on the phenotype, or the
observable characteristics of an organism, but
the genetic (heritable) basis of any phenotype that gives a
reproductive advantage may become more common in a
population (see allele frequency). Over time, this process can
result in populations that specialise for
particular ecological niches (microevolution)
and may eventually result in theemergence
of new species (macroevolution). In
other words, natural selection is an important
process (though not the only process) by
which evolution takes place within a population
of organisms. Natural selection can be contrasted with artificial
selection, in whichhumans intentionally choose specific traits
(although they may not always get what they want). In natural
selection there is no intentional choice. In other words,
artificial selection is teleological and natural selection is not
teleological, though biologists often use teleological
language to describe it.

10. THANK YOU