The key difference between trisomy and triploidy is that the trisomy is a condition that an organism is having an extra chromosome making the total as 47 while triploidy is a condition that an organism is having an entire extra set of chromosome making the total as 69.
The human genome consists of a total of 46 chromosomes, and they exist in pairs. Hence, there are 23 chromosome pairs inside the human nucleus. Among these pairs, 22 are autosomes, which are responsible for somatic characteristics while one pair is sex chromosomes that are responsible for determining sex and sex-related characteristics. Furthermore, genetic information passes from parent to offspring during reproduction. For this purpose, the genome should be replicated and correctly pass into gametes.
Sometimes, errors can happen in this process. These errors cause chromosomal aberrations or chromosome number changes. Aneuploidy and polyploidy are two types that change the chromosome number. In aneuploidy, chromosome number changes in one. In polyploidy, multiple numbers of chromosomes change in the genome. Trisomy is an aneuploidy condition while triploidy is a polyploidy condition that changes the number of chromosomal sets. Therefore, the difference between trisomy and triploidy mainly depend on the number of chromosomes changes within the genome.
CONTENTS
1. Overview and Key Difference
2. What is Trisomy
3. What is Triploidy
4. Similarities Between Trisomy and Triploidy
5. Side by Side Comparison – Trisomy vs Triploidy in Tabular Form
6. Summary
What is Trisomy?
Trisomy is an aneuploidy condition. In this condition, the genome consists of an extra chromosome. It is the condition that an organism has 2n+1 chromosome number. In simple words, in trisomy, an organism has a total of 47 chromosomes instead of 46 chromosomes. One single chromosome has been added to the genome of the organism. It is a type of chromosomal abnormality.
Figure 01: Trisomy
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.
What is Triploidy?
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.
Figure 02: Triploidy
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.
What are the Similarities Between Trisomy and Triploidy?
- Trisomy and Triploidy are chromosomal abnormalities.
- Both disorders show birth defects and lead to different syndromes.
- In both conditions, one gamete consists of an abnormal number of chromosomes.
What is the Difference Between Trisomy and 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.
Summary – Trisomy vs Triploidy
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 69. This is the difference between trisomy and triploidy.
Reference:
1.Department of Health & Human Services. “Trisomy Disorders.” Better Health Channel, Department of Health & Human Services, 30 Aug. 2013. Available here
2.“Triploid Syndrome.” Wikipedia, Wikimedia Foundation, 6 Aug. 2018. Available here
Image Courtesy:
1.”Trisomy due to nondisjunction in maternal meiosis 1″By Wpeissner – Own work, (CC BY-SA 3.0) via Commons Wikimedia
2.”Triploidsyndrome” (Public Domain) via Commons Wikimedia