You may be surprised to hear that potatoes, gorillas and deer mice have 48 individual chromosomes. Even more surprising, carp have chromosomes, rattlesnake fern has chromosomes and black mulberry has Clearly, the number of chromosomes does not correlate with the apparent complexity of the organism. Additionally, you cannot distinguish species through the number of chromosomes alone. In fact, the number of chromosomes in an animal or plant is determined by complete randomness. Chromosome numbers can decrease through fusion or increase through polyploidy — therefore making newer species have a different number of chromosomes than their ancestors.
Fusion occurs when two chromosomes stick together by accident and is the most likely explanation of how chimps evolved to become humans. Scientists have found that human chromosome 2 looks like two chimp chromosomes that fused together, which indicates that this may have been the way we changed from our primate cousins to the humans we are today. Polyploidy, on the other hand, occurs through an error in cell division. Sperm and eggs, or sex cells, divide through a mechanism known as meiosis.
During this process, the DNA is condensed into their neat chromosome packages and the chromosomes are pulled to opposite sides of the cell, which then divides into two new cells. Sometimes a mistake occurs where chromosomes are not pulled apart properly, thus leading to new cell with more chromosomes than usual. If this cell is then fertilized by a sperm, then the new organism will end up with more chromosomes than its ancestors.
In humans, this is often a fatal error and the fetus does not survive. Among those, there are two sex-determining chromosomes, and 22 pairs of autosomal, or non-sex, chromosomes. The total number of chromosomes in diploid cells is described as 2n, which is twice the number of chromosomes in a haploid cell n. Further Exploration Concept Links for further exploration haploid cell chromosome cell division principle of independent assortment gamete Principles of Inheritance.
Related Concepts 7. Scientists have numbered the chromosome pairs from 1 to 22, with the 23rd pair labeled as X or Y, depending on the structure. The first 22 pairs of chromosomes are called autosomes. The 23rd pair of chromosomes are known as the sex chromosomes, because they decide if you will be born male or female. For instance, some individuals may have an abnormality in their genetic sequence resulting in a particular medical condition.
Such conditions are called genetic disorders, examples of which are the blood disorders sickle cell disease and thalassemia. Other medical conditions, such as type II diabetes, might be associated with particular genes or genetic sequences. Knowing who has these may help get better and faster treatment.
Just like the volunteers that helped the human genome project, these volunteers will be helping researchers to know more about genes and helping improve health. Skip to main content. English Bangla Urdu. Follow us on twitter.
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