Not yet answered Marked out of 2.00 Flag question Explain the difference between euploidy and aneuploidy.
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Correct Answer
Euploidy is the condition where an organism or cell has a chromosome number that is an exact multiple of the basic haploid number (n), meaning it contains one or more complete sets of chromosomes. Aneuploidy is the condition where an organism or cell has an abnormal number of chromosomes that is not an exact multiple of the haploid set, due to the gain or loss of one or more individual chromosomes.
Explanation
The fundamental distinction between euploidy and aneuploidy relates to the scale of the change in an organism’s chromosome count.
Euploidy (from the Greek roots “eu” meaning true and “ploid” meaning set) describes a state where the chromosome number is a precise multiple of the basic, or haploid, number (n). A normal diploid organism, like a human, has two complete sets of chromosomes (2n). Other euploid states include haploidy (n), as seen in gametes, and polyploidy, which involves having more than two complete sets, such as triploidy (3n) or tetraploidy (4n). In all euploid conditions, the relative proportion of genes across the different chromosomes remains balanced, even if the total number of gene copies changes. While polyploidy is generally lethal in animals, it is a common and often beneficial evolutionary mechanism in plants, leading to larger fruits or flowers.
In contrast, aneuploidy (“an” meaning not) refers to a numerical abnormality affecting only certain chromosomes, not the entire set. It arises from the gain or loss of one or more individual chromosomes, resulting in a total number that is not a multiple of ‘n’. This condition is typically caused by an error called nondisjunction during cell division (meiosis or mitosis), where homologous chromosomes or sister chromatids fail to separate correctly.
The most common types of aneuploidy are trisomy (2n + 1), the presence of an extra chromosome, and monosomy (2n – 1), the absence of a single chromosome. Famous examples in humans include Trisomy 21, which causes Down syndrome, and Monosomy X, which causes Turner syndrome. Unlike the balanced state of euploidy, aneuploidy creates a significant gene dosage imbalance. This imbalance disrupts normal development and cellular function, which is why aneuploid conditions are almost always detrimental and are a leading cause of miscarriages and genetic disorders
