Question

The diploid number of chromosomes in plant species A is 8 ; the diploid number in plant species \(\mathrm{B}\) is 16 . If plant species \(\mathrm{C}\) originated when a hybrid between \(\mathrm{A}\) and \(\mathrm{B}\) spontaneously doubled its chromosome number, what is the most likely number of diploid chromosomes in C? a. 8 b. 12 c. 24 d. 48

Short answer

The most likely number of diploid chromosomes in plant species C is 24, which is option c.

Step-by-step solution

- Understanding diploid number

The diploid number (2n) refers to the total number of chromosomes in a somatic cell. For plant species A, the diploid number is given as 8, and for species B, it is 16.

- Calculating the haploid number

The haploid number (n) is half of the diploid number. Therefore, species A has a haploid number of 4 (8/2), and species B has a haploid number of 8 (16/2).

- Hybrid formation

When species A and species B cross, their haploid numbers combine. This hybrid will therefore have 4 chromosomes from species A and 8 chromosomes from species B, resulting in a hybrid with 12 chromosomes (4 + 8).

- Chromosome doubling

The problem states that the hybrid’s chromosome number spontaneously doubles. Therefore, the hybrid will now have 24 chromosomes (12 * 2).

- Most likely number of diploid chromosomes in species C

Given the doubling of chromosomes in the hybrid, the diploid number of chromosomes in plant species C is most likely 24.

Key concepts

Diploid Number

The diploid number, denoted as 2n, is the total number of chromosomes found in a somatic (non-reproductive) cell of an organism. It's important to note that this count includes two complete sets of chromosomes, one from each parent.

For instance, in plant species A, the diploid number is given as 8. This means there are 8 chromosomes in each somatic cell, with 4 chromosomes inherited from each parent. In plant species B, the diploid number is higher at 16, indicating that these cells contain 16 chromosomes in total, with 8 inherited from each parent.

Understanding the diploid number of an organism helps us determine its genetic make-up and potential behavior during reproduction.

Haploid Number

The haploid number, represented as n, is half of the diploid number and reflects the number of chromosomes in a reproductive cell (such as a sperm or egg cell). These cells contain just one set of chromosomes.

For the given plant species A, with a diploid number of 8, the haploid number is 4 (i.e., 8 / 2). This means each reproductive cell of species A contains 4 chromosomes.

Similarly, in plant species B, with a diploid number of 16, the haploid number is 8 (i.e., 16 / 2). Each reproductive cell of species B contains 8 chromosomes. The haploid number is crucial for understanding how genetic material is transferred during sexual reproduction and hybridization.

Chromosome Hybridization

Chromosome hybridization occurs when two species interbreed. This process involves the combining of chromosomes from the reproductive cells (gametes) of both parent species to form a hybrid.

In this exercise, species A (with a haploid number of 4) and species B (with a haploid number of 8) mate, resulting in a hybrid that receives 4 chromosomes from species A and 8 chromosomes from species B. Therefore, the hybrid will have a total of 12 chromosomes.

This new combination can lead to unique genetic traits in the hybrid, influencing its characteristics and adaptability.

Plant Genetics

Plant genetics is the study of genes, genetic variation, and heredity in plants. Understanding plant genetics helps scientists develop better crops, increase yield, and enhance resistance to diseases and environmental stresses.

In the context of this exercise, understanding plant genetics involves analyzing the process of chromosome doubling in a hybrid. When the chromosome number in the hybrid (initially 12) spontaneously doubles, it results in 24 chromosomes. This event can stabilize the hybrid, enabling it to reproduce effectively and become a new species, designated here as species C.

Plant genetics blends classical breeding techniques with modern molecular biology to solve agricultural challenges and improve plant traits for better production and sustainability.