Chromosome
Various genetic traits are passed from parents or ancestors to their offspring or descendants. Genes are proteins that construct the human genome, which determines the genetic composition of an individual and can consist of up to 25,000 genes. The human genome is also based upon 23 chromosome pairs, one of which determines an individual’s sex whilst the others are autosomal chromosome pairs. A chromosome, therefore, is a strand of DNA that consists of a number of genes, which are encoded with an individual’s hereditary information, and other regulatory functions and proteins. In bacteria, by contrast, a chromosome is unlike a human chromosome in that instead of having a coiled threadlike structure, it is more circular and simply contains the hereditary information for cell development.
The number of chromosomes present in an organism will not necessarily determine how advanced the creature is – at least not always! Indeed, whilst the common variety fruit fly has just eight chromosomes in total, humans have an impressive 46 (23 chromosome pairs comprising the human genome, as mentioned above). However, the number of chromosomes merely describes the genetic framework upon which the creature has evolved – the substance of the inherited information is key, therefore. If the reverse was true, the kingfisher would be among the most advanced creatures on the planet with a whopping 132 chromosomes. Moreover, these figures refer to the number of chromosomes in a cell nucleus and not those that exist in the entire organism. Finally, the importance of chromosomes in the development of healthy organisms is made evident by the presence of chromosomal abnormalities, which can cause various genetic conditions such as Downs syndrome.
