Problem 6 - Campbell Biology

Question

Application/analysis Plant species A has a diploid chromosome number of \(12 .\) Plant species \(B\) has a diploid number of \(16 .\) A new species, \(C\) , arises as an allopolyploid from A and B. The diploid number for species Cwould probably be (A) 14. \(\quad\) (B) 16. \(\quad\) (C) 28. \(\quad\) (D) 56.

Step-by-Step Solution

Answer

The diploid number for species C is 28, so the correct answer is (C).

Step 1: Understand the Problem

We need to determine the diploid chromosome number of a new species, C, that arises as an allopolyploid from two parent species, A and B. We'll start by understanding the diploid chromosome numbers of each parent species.

Step 2: Identify Diploid Numbers in Parents

Species A has a diploid chromosome number of 12. Species B has a diploid chromosome number of 16.

Step 3: Concept of Allopolyploidy

Allopolyploidy involves the combination of the chromosome sets from two different species. The new species, C, will have a combination of the chromosome sets from species A and B.

Step 4: Calculate Diploid Number for Species C

For species C, the diploid number will be the sum of the diploid numbers of species A and B because an allopolyploid contains the full chromosome sets from both parent species. Therefore, the diploid number for species C is: Diploid number of species A: 12 Diploid number of species B: 16 Adding these together: 12 + 16 = 28

Step 5: Choose the Correct Answer

Based on the calculation, the diploid number for species C would be 28. Hence, the correct answer is (C) 28.

Key Concepts

Diploid Chromosome Number

When studying plant genetics, the term 'diploid chromosome number' refers to the total number of chromosomes found in somatic (non-reproductive) cells of an organism. In simple terms, a diploid cell contains two complete sets of chromosomes, one from each parent. These sets are homologous, meaning each chromosome from one set has a corresponding chromosome in the other set. For instance, in humans, the diploid number is 46, with 23 chromosomes from each parent. Drawing from the exercise, we see that species A has a diploid chromosome number of 12 and species B has 16. These numbers are important for understanding how new species can form through processes like allopolyploidy, as they provide the genetic material necessary for combination.

Species Hybridization

Species hybridization is a fascinating occurrence where two different species interbreed to produce a hybrid organism. In plants, this normally happens through the fusion of gametes (sperm and egg cells) from different species. This hybridization process can result in hybrids that carry genetic information from both parent species, which can sometimes lead to new species if the hybrid is fertile and stable. In the context of the given problem, species A and B interbreed, bringing their unique set of chromosomes to form species C. Such interspecies hybridization can increase genetic diversity and potentially create plants with desirable traits, such as disease resistance or improved adaptability to environmental changes.

Chromosome Sets

A chromosome set, or genome, is a complete set of chromosomes from one parent. In diploid organisms, each cell possesses two sets of chromosomes, one from each parent. When it comes to creating a new species through allopolyploidy, multiple genome sets are involved. Allopolyploidy specifically refers to the combination of chromosome sets from different species. In the given exercise, species C arises as an allopolyploid of species A and B. Therefore, species C will have the complete chromosome sets of both parents. As calculated, the chromosome sets of species A (12 chromosomes) and species B (16 chromosomes) will combine to form 28 chromosomes in species C. This combined chromosome number explains why the correct diploid number for species C is 28.