Explain how and why Genetic diversity increases through the processes of Crossing Over and Mutations.
Crossing Over -
Crossing over allows exchange of parts of chromosomes. This mixing and matching allows for new combinations of genes in a population. If this did not happen then â€œpopulationsâ€? of species would be less diverse. For example, a diploid organism, in this case a mouse, (having two copies of every chromosome) has a chromosome with the genes for eye color, and also the genes for fur color. If the mouse is heterozygous for eye color; the dominant R producing red eyes and the recessive giving brown eyes, and it is also heterozygous for fur color with a dominant F making white fur and the recessive f giving brown fur. One copy of the chromosome has the R and F alleles, and the other has the r and f alleles. If there is no crossing over, then R and F are always inherited together as are r and f. This means that any of the mousesâ€™s offspring with white fur will always have red eyes. If there was crossing over then the offspring could have brown fur and red eyes.
What is a mutation?
The diversity of beetle species as seen in the picture is driven by genetic mutation. Mutations are changes in the genetic sequence, and they are a main cause of diversity among organisms. These changes occur at many different levels, and they can have widely differing consequences. There are two general types of mutations: point (gene) mutations and chromosomal mutations. Point mutations affect only one or a few nucleotides within a gene Chromosomal mutations change the number of chromosomes or the number or arrangement of genes in a chromosome (= change in chromosome structure) In biological systems that are capable of reproduction, we must first focus on whether they are inheritable; specifically, some mutations affect only the individual that carries them, while others affect all of the carrier organism's offspring, and further descendants. For mutations to affect an organism's descendants, they must: 1) occur in cells that produce the next generation, and 2) affect the hereditary material. Ultimately, the interplay between inherited mutations and environmental pressures generates diversity among species.