What is Trisomy — Definition, Facts, Examples 2. What is Triploidy — Definition, Facts, Examples 3. Trisomy refers to the condition of having an additional copy of a chromosome in the genome.
This means a particular chromosome of the nucleus occurs in triplets in trisomy. Trisomy is a type of aneuploidy. Typically, trisomy arises as a result of non-disjunction of homologous chromosomes during the production of gametes by meiosis. The gametes formed in trisomy consist of 24 chromosomes instead of Generally, trisomy can occur in any chromosome of the genome.
But, most of them are lethal except in chromosomes 13, 18, 21, X and Y. Maternal age is a risk factor of non-disjunction. Trisomy 21 or Down syndrome is the commonest, viable trisomy. The karyotype of the Down syndrome is shown in figure 1.
Trisomy 13 or Patau syndrome and trisomy 18 or Edward syndrome are rare types of trisomies that cause severe congenital malformations. They also cause mental retardation, resulting in death within a few months of birth.
Trisomy leads to the formation of imbalanced amounts of gene products. Triploidy refers to the presence of an extrachromosomal set in diploid organisms. This means the number of chromosome sets in the nucleus is three in triploidy. Triploidy is a type of euploidy. Triploidy is a very rare chromosomal disorder in humans. In triploid humans, 69 chromosomes are present in the nucleus. Generally, the human genome 2n consists of 46 chromosomes. Maternal triploidy occurs due to the fertilization of a diploid ovum by a haploid sperm.
Other than that, triploidy occurs due to the complete non-disjunction of chromosomes during meiosis. Most conceptions with triploidy in humans do not survive till birth.
The triploid condition of a nucleus is shown in figure 2. Triploidy is more common in plants. In plants, triploidy mainly arises due to interspecies crosses where the gametes are fused from distinct species distinct species.
Trisomy occurs as a result of nondisjunction of homologous chromosomes during the sex cell formation by meiosis. Therefore, an egg cell or a sperm cell can have a total of 24 chromosomes. When unites this type of a sex cell with the opposite sex cell, resulting zygote will have a total of 47 chromosomes which refers to trisomy.
Important to note here is, the trisomy makes a huge impact on organisms causing lethal syndromes such as Down syndrome trisomy of chromosome 21 , Edward syndrome trisomy of chromosome 18 , Triple X syndrome Sex chromosomes XXX , Klinefelter syndrome sex chromosome XXY and Patau syndrome trisomy of chromosome 13 , etc.
When children affected with trisomy, they show development delays, birth defects, intellectual disabilities etc. Triploidy is a chromosomal disorder where a fetus possesses an entire extra set of chromosomes.
A normal set of the chromosome has 23 chromosomes in a haploid cell n. When it is two sets, it becomes 46 2n. When triploidy occurs, it becomes a total of 69 chromosomes 3n. Therefore, in triploidy, one gamete consists of 23 chromosomes while the opposite sex gamete contains 46 chromosomes. When they unite, they create a 3n zygote which contains 69 chromosomes. Each chromosome exists in three copies instead of two copies. This types of infants miscarriages during the early pregnancy.
If triploidy infants survive, they show birth defects such as growth retardation, heart defects and neural tube defects. Triploidy can be seen in some cells. In that condition, it is not a severe problem, and it is known as mosaic triploidy. When the fetus receives an extra chromosome, it is a condition called trisomy while when a fetus receives an entire extra set of chromosomes, it is a condition called triploidy. In both conditions, the fetus has an abnormal number of chromosomes. Therefore, the main difference between trisomy and triploidy is the total number of chromosomes.
Trisomy has 47 chromosomes whereas triploidy has 69 chromosomes. The below infographic shows further details on the difference between trisomy and triploidy in tabular form. Due to some errors in the gamete formation, the zygote can receive an abnormal number of chromosomes.
Trisomy and triploidy are two chromosomal abnormalities. Trisomy refers to the condition which possesses an extra chromosome while triploidy refers to the condition which possesses an entire extra set of chromosomes. Therefore in trisomy total number of chromosomes is 47 while in triploidy it is This is the difference between trisomy and triploidy.
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