Overall, the main sources of genetic variation are the formation of new alleles, the altering of gene number or position, rapid reproduction, and sexual reproduction.

Genetic variation refers to diversity in gene frequencies. Genetic variation can refer to differences between individuals or to differences between populations. Mutation is the ultimate source of genetic variation, but mechanisms such as sexual reproduction and genetic drift contribute to it as well.

For a given population, there are three sources of variation: mutation, recombination, and immigration of genes.

The three main sources of genetic variation arising from sexual reproduction are: Crossing over (in prophase I) Random assortment of chromosomes (in metaphase I) Random fusion of gametes from different parents.

Genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism’s offspring).

Several basic modes of inheritance exist for single-gene disorders: autosomal dominant, autosomal recessive, X-linked dominant, and X-linked recessive. However, not all genetic conditions will follow these patterns, and other rare forms of inheritance such as mitochondrial inheritance exist.

A gene is the basic physical and functional unit of heredity. Genes are made up of DNA. Some genes act as instructions to make molecules called proteins. In humans, genes vary in size from a few hundred DNA bases to more than 2 million bases.

Mendel’s law of independent assortment states that the alleles of two (or more) different genes get sorted into gametes independently of one another. In other words, the allele a gamete receives for one gene does not influence the allele received for another gene.

We know now that some hereditary factors are codominant, not completely dominant, to others–one can cross red with white petunias and get pink offspring, not the red or white ones that Mendel would have predicted. We also know that the law of segregation is not always true in its literal sense.

The law of segregation states that each individual that is a diploid has a pair of alleles (copy) for a particular trait. Each parent passes an allele at random to their offspring resulting in a diploid organism. The allele that contains the dominant trait determines the phenotype of the offspring.

A: The rules of Mendel’s inheritance: In a cross between pure contrasting traits, the dominant trait will be observed in the phenotype of the organism whilst the recessive trait will be concealed. Only a single gene copy is allocated in a gamete cell and this is carried out in a random manner.

Gregor Mendel, through his work on pea plants, discovered the fundamental laws of inheritance. He deduced that genes come in pairs and are inherited as distinct units, one from each parent. Offspring therefore inherit one genetic allele from each parent when sex cells unite in fertilization.

The way in which traits are passed from one generation to the next-and sometimes skip generations-was first explained by Gregor Mendel. By experimenting with pea plant breeding, Mendel developed three principles of inheritance that described the transmission of genetic traits, before anyone knew genes existed.

Mendel’s laws and meiosis Mendel’s laws (principles) of segregation and independent assortment are both explained by the physical behavior of chromosomes during meiosis. Random, independent assortment during metaphase I can be demonstrated by considering a cell with a set of two chromosomes (n = 2).

We now know that Mendel’s inheritance factors are genes, or more specifically alleles – different variants of the same gene. In today’s genetic language, a pure-breeding pea plant line is a homozygote – it has 2 identical copies of the same allele.