Ploidy facts for kids
Ploidy is a word used in genetics and cell biology. It describes how many sets of chromosomes a cell has. Think of chromosomes like instruction books for a cell.
Most living things, called eukaryotes, usually have either one set of chromosomes or two sets.
- If a cell has one set, it's called haploid.
- If a cell has two sets, it's called diploid. This means it has one set from each parent.
Some organisms are polyploid. This means they have more than two sets of chromosomes. For example:
- Some amphibians are triploid, meaning they have three sets.
- The cells inside the seeds of many plants are also triploid.
- Some types of trout or salmon are tetraploid (four sets).
- Wheat can have six sets (hexaploid).
- Certain sturgeons and strawberries can have eight sets (octoploid).
- A plant called plumed cockscomb (Celosia argentea) can have 12 sets (dodecaploid).
Sex cells, also known as gametes, are almost always haploid. If an adult organism is polyploid, its gametes will have half the number of chromosome sets.
What is Polyploidy?
Polyploidy happens when cells or organisms have more than two matching sets of chromosomes.
Most organisms are normally diploid. This means they have two sets of chromosomes. They get one set from their mother and one set from their father. Polyploidy can happen because of unusual cell division.
It is most common in plants, but it can also happen in animals. Scientists believe that 30% to 80% of all plant species alive today are polyploid. Many plant groups also show signs of having been polyploid a long time ago.
Big increases in the variety of flowering plants have happened at the same time as ancient chromosome duplications. About 15% of flowering plant species and 31% of fern species became new species because their ploidy increased.
Polyploid plants can appear naturally. Many polyploid plants are stronger than their parent species. They might also show new features or shapes. These new traits can help them form new species and live in new environments.
Polyploidy can happen very quickly, sometimes in just one generation. This is different from the idea that evolution always happens slowly. However, many genetic changes can still happen in a species after it becomes polyploid.
How Gametes Work in Polyploids
The gametes (sex cells) of polyploid organisms are special. They can carry several sets of chromosomes.
For example, common wheat is a polyploid plant. It has six sets of chromosomes. These six sets originally came from three different plant species. So, most cells in a wheat plant have six sets of chromosomes. But its gametes (like pollen or egg cells) have three sets of chromosomes.
Related pages
- Aneuploidy: When a cell has a few more or a few less chromosomes than the usual number for that species.
- Karyotype
- Haplodiploidy
