Three Characteristics Of Homologous Chromosomes

Homologous Chromosomes Definition

Homologous chromosomes are two pieces of DNA inside a diploid organism which carry the same genes, i from each parental source.

In simpler terms, both of your parents provide a complete genome. Each parent provides the same 23 chromosomes, which encode the same genes. So, our cells carry 46 total chromosomes, in 2 copies. However, each homologous chromosome can provide a different version of each gene. Two versions of each gene create more than variety, lower the detrimental effects of negative mutations, and generally stabilize a population.

Homologous Chromosome Function

Two Versions of Each Gene

Diploid organisms, like humans, carry two copies of the genome in each i of their cells. Having ii copies of each chromosome, called homologous chromosomes, helps increase both the diverseness and stability of a species. While each homologous chromosome carries the same genes, they can carry different versions of the factor. Dissimilar versions of a gene are chosen alleles.

This ways that your cells will typically produce two versions of every protein encoded by the Dna. Some versions volition work better than others. Further, the combination of good and bad proteins produces different phenotypic effects that increase the diverseness within a population. Some alleles have a dominant/recessive relationship, in which the dominant gene is the only one that shows. Others have more than complex relationships, and different combinations of alleles can produce vastly different furnishings on an organism. This is important considering multifariousness helps populations survive in the face of environmental changes.

Homologous Recombination

Lastly, homologous chromosomes take office in a procedure known as homologous recombination during the formation of gametes. This process is besides known as "crossing over", because parts of the homologous chromosomes are exchanged when they come up into shut contact. The chromosomes contain the same genes, which are more often than not the same length and size. These sections can easily exist transferred between chromosomes. The prototype below shows recombination:

In this image, each chromosome has already been replicated in preparation for meiosis. However, two of the chromatids have exchanged genetic textile. This procedure is extremely of import for the creation and maintenance of variety within a population. For example, if red is the paternal chromosome and blue is maternal, the genes they conduct will no longer exist linked. Just considering your father had bluish eyes and black hair does not mean you will automatically inherit these traits. Homologous recombination ensures that traits are randomly mixed together, from both parental sources.

Homologous Chromosome Examples

In a Simple Organism

The image below shows a unproblematic organism. This organism is diploid, simply only has a 1 pair of chromosomes. These are homologous chromosomes, because they carry the same genes. Even so, they can carry dissimilar alleles of each gene, shown by their internal pattern. This organism tin can reproduce asexually, simply by duplicating the DNA and dividing the cell. In this example, the organism remains haploid. This is shown in the top portion of the diagram.

The bottom portion of the image shows the production of gametes for sexual reproduction. Meiosis is the process used to create gametes. Meiosis creates haploid cells, which can be combined with gametes from another organism to class a new diploid organism. Haploid organisms have only ane re-create of the DNA, therefore, they exercise not have homologous chromosomes. When these gametes pair upwardly and bring together together, they volition once more exist in the aforementioned cell with a new homologous pair.

In Humans

As with the unproblematic hypothetical organism above, humans too have homologous chromosomes. 1 one-half of each pair comes from our mother, while the other comes from our father. These chromosomes are carried in the haploid gamete cells, sperm and eggs. When a sperm meets an egg, fertilization occurs and a diploid organism is formed. This zygote, like the organism above, volition split many times to create all of the cells of our trunk. Each cell in your body, then, contains 23 pairs of homologous chromosomes, or 46 total chromosomes. The image below shows a man karyotype, or visualization of the condensed chromosomes. Notice how each pair has a similar shape and dye pattern. This is because each of these homologous chromosomes carries the same genes.

Every bit nosotros become sexually mature, the human body starts to produce and release gametes. These gametes take been reduced to haploid cells, after first existence mixed up and recombined in different arrangements. This means that children will accept a mixture of traits not necessarily seen in their parents or grandparents. In fact, some combinations of traits volition be completely new thanks to homologous chromosomes and how they help usa reproduce.