How does independent assortment happen

This point of contact is deemed the chiasmata and can allow the exchange of genetic information between chromosomes. This further increases genetic variation. There are also many other ways in which genetic variation is increased in a species gene pool, all of which are described in the following pages. The next tutorial investigates the work of Gregor Mendel , an Austrian monk famous for his work involving monohybrid and dihybrid crossing, alongside the continuation into looking at genetic diversity through meiosis and genetics in general.

It has two sections. The first is a fill-in-the-gaps test about crossing over and the second is a matching type about Mendelian Law of Independent Assortment.

Select from the following word s :. This tutorial describes the sigmoid curve, annual plant growth, tree growth, human growth, and insect growth as the grow.. Read this tutorial to know more about this form of i.. A running water environment offers numerous microhabitats for many types of animals. Similar to plants, animals in lotic.. Humans are diploid creatures. This means that for every chromosome in the body, there is another one to match it.

This tutorial presents Gregor Mendel's law of dominance. Learn more about this form of inheritance and how it can be pre.. During prophase I, chromosomes condense and become visible inside the nucleus. As the nuclear envelope begins to break down, homologous chromosomes move closer together. The synaptonemal complex, a lattice of proteins between the homologous chromosomes, forms at specific locations, spreading to cover the entire length of the chromosomes.

The tight pairing of the homologous chromosomes is called synapsis. In synapsis, the genes on the chromatids of the homologous chromosomes are aligned with each other. The synaptonemal complex also supports the exchange of chromosomal segments between non-sister homologous chromatids in a process called crossing over. The crossover events are the first source of genetic variation produced by meiosis. A single crossover event between homologous non-sister chromatids leads to an exchange of DNA between chromosomes.

Following crossover, the synaptonemal complex breaks down and the cohesin connection between homologous pairs is also removed. At the end of prophase I, the pairs are held together only at the chiasmata; they are called tetrads because the four sister chromatids of each pair of homologous chromosomes are now visible.

During metaphase I, the tetrads move to the metaphase plate with kinetochores facing opposite poles. The homologous pairs orient themselves randomly at the equator. This event is the second mechanism that introduces variation into the gametes or spores. In each cell that undergoes meiosis, the arrangement of the tetrads is different.

The number of variations is dependent on the number of chromosomes making up a set. There are two possibilities for orientation at the metaphase plate. The possible number of alignments, therefore, equals 2 n , where n is the number of chromosomes per set.

Given these two mechanisms, it is highly unlikely that any two haploid cells resulting from meiosis will have the same genetic composition. In humans, there are over 8 million configurations in which the chromosomes can line up during metaphase I of meiosis. It is the specific process of meiosis, resulting in four unique haploid cells, that results in these many combinations. This independent assortment, in which the chromosome inherited from either the father or mother can sort into any gamete, produces the potential for tremendous genetic variation.

Together with random fertilization, more possibilities for genetic variation exist between any two people than the number of individuals alive today. For example, when Mendel crossed plants with round yellow peas to plants with wrinkled green peas, all of the F1 peas expressed the dominant traits round and yellow. In the F2, along with round yellow and wrinkled green peas, he observed round green and wrinkled yellow peas.

The four possible combinations of color and shape appeared in the ratio of , which represents the independent assortment of the genes for the two pairs of traits into the gametes. The proportions of the other three combinations can be similarly calculated.

Later, after the discovery of chromosomes, and of their behavior in meiosis , it was possible to explain independent assortment as a consequence of the independent movement of each pair of homologous chromosomes during meiosis. An independent assortment of genes is important to produce new genetic combinations that increase genetic variations within a population. What is independent assortment as explained with a suitable example?

The dominant allele for the eye color, for example, is brown eyes B , and the recessive allele, green eye color b. Heterozygous cats with dominant traits, brown eyes and white fur, will produce gametes at sexual maturity.

During gamete production, the alleles for eye color will be sorted independent of the alleles for the fur color, if we are to base it on the law of segregation. The resulting gamete after meiosis will contain random alleles such that when two heterozygous cats are crossed, their offspring will likely have mixed traits.

One of the kitten, for example, could have brown eye color BB or Bb and grey fur color ww. Another kitten might have green eyes bb and grey fur ww. Now, this is just an illustrative example.

In nature, the eye and fur color traits are polygenic , meaning several alleles are involved in determining the phenotype of the offspring.

The independent assortment is now explained according to the behavior of chromosomes during meiosis and the random movement of each homologous pair of chromosomes during meiosis. Independent assortment is an important process for the production of new genetic combinations that contribute to the genetic diversity among individuals that reproduce sexually. How do you know if a chromosome is homologous? Join our Forum now! Try to answer the quiz below to check what you have learned so far about Independent assortment.

Quiz Choose the best answer. Explore more about homologous chromosome. This tutorial describes the independent assortment of chromosomes and crossing over as important events in meiosis. Read this tutorial to know more details in each of these meiotic events and how they promote genetic diversity in sexually-reproducing organisms Read More.

Humans are diploid creatures. This means that for every chromosome in the body, there is another one to match it. However, there are organisms that have more than two sets of chromosomes. The condition is called polyploidy. Know more about this topic through this tutorial Read this tutorial to know more about this form of inheritance Gregor Mendel, an Austrian monk, is most famous in this field for his study of the phenotype of pea plants, including the shape of the peas on the pea plants.

Know the works of Mendel that set the foundation of genetics. Skip to content Main Navigation Search. Dictionary Articles Tutorials Biology Forum. Table of Contents. When does independent assortment occur? The independent assortment of chromosomes is a result of the independent division of chromosomes into separate gametes.