If the haploid number for a plant species is 4, how many chromosomes are found in a member of the species that has one of the following characteristics? Explain your reasoning in each case.
Triploidy

Verified step by step guidance

1. Understand the concept of haploid number: The haploid number (n) represents the number of chromosomes in a single set of the organism's genome. For this plant species, the haploid number is given as 4 (n = 4).
2. Define triploidy: Triploidy refers to a condition where an organism has three complete sets of chromosomes instead of the usual two sets found in diploid organisms. This means the organism has 3n chromosomes.
3. Calculate the total number of chromosomes in a triploid individual: Multiply the haploid number (n = 4) by 3 to determine the total number of chromosomes in a triploid organism. The formula is: $3\times \mathrm{n}$.
4. Substitute the haploid number into the formula: Replace n with 4 in the formula to calculate the total number of chromosomes. The calculation becomes: $3\times 4$.
5. Conclude the reasoning: The triploid individual has three sets of chromosomes, which is consistent with the definition of triploidy. This calculation provides the total number of chromosomes in the organism.

Key Concepts

Haploid and Diploid Numbers

The haploid number (n) refers to the number of chromosomes in a gamete, which is half the total number of chromosomes in a diploid organism. In this case, if the haploid number for the plant species is 4, the diploid number (2n) would be 8, representing the total chromosomes in somatic cells.

Triploidy

Triploidy is a condition where an organism has three sets of chromosomes instead of the usual two. For a species with a haploid number of 4, a triploid individual would have 3n, which equals 12 chromosomes. This condition can occur due to errors in cell division or fertilization.

Chromosome Number Calculation

To determine the chromosome number in different ploidy levels, one can use the formula based on the haploid number. For triploidy, the formula is 3n, where n is the haploid number. Thus, for this plant species with n=4, the calculation would yield 3 x 4 = 12 chromosomes in a triploid individual.