Which two of the following statements about genetic variation are correct?
1 - Asexual reproduction always produces genetic variation.
2 - Gamete production is the only possible source of genetic variation in sexual reproduction.
3 - The environment can cause genetic variation.
4 - Mutations can produce genetic variation.
A) 1 and 2 only
B) 1 and 3 only
C) 1 and 4 only
D) 2 and 3 only
E) 2 and 4 only
F) 3 and 4 only
Hi,
I don’t understand how the environment causes genetic variation. I know it affects gene expression (epigenetics) and there’s plenty of examples for that like human skin color (melanin production in response to uv exposure) or hydrangea flowers colors, that however is not genetic variation as it doesn’t change the genotypes within an organism or the alleles of a population on its own.
First thing that came to my mind was mutagens. Mutagens cause mutations which can produce genetic variation. Often mutagens are enviromental factors such as radiation chemicals and so on. But I’m not sure
There are three main sources for genetic variation:
Mutations
Crossing over in prophase I, and independent assortment in metaphase I
Fusion of gametes of two different parents in sexual reproduction
These three sources create new alleles. The Environment can induce one of these three sources to occur, for example:
Mutations - agnets that cause mutations are called mutagens. Mutagens can take many forms like: physical mutagens (e.g UV radiation, X-rays, and radioactive decay), chemical mutagens (e.g reactive oxygen species, and reactive metals like arsenic), and biological mutagens (e.g viruses, and bacteria).
Gene Flow - The environment can place pressure in various ways (predators, resources, temperature, etc.) on organisms to move and mix with other populations of the same species. This leads to variation in the gene pools of the respective populations.
Now as for natural selection, natural selection selects for beneficial traits that already exist in a population. Natural selection results in changes to the allele frequency in a population, but on its own it does not create new alleles. Evolution is the collective effort of all that I’ve mentioned and more and thus does create genetic variation, and natural selection is the main driving force for evolution, but it is not a source that creates new alleles, however it is what facilitates the selection of new beneficial alleles and their prevalence generations down the line.
