Problem 11 - Biology

Question

The pea plants used in Mendel's genetic inheritance studies were diploid, with 14 chromosomes in somatic cells. Assuming no crossing over events occur, how many unique gametes could one pea plant produce? a. 28 b. 128 c. 196 d. 16,384

Step-by-Step Solution

Answer

128

Step 1: Determine Chromosome Pairs

Since pea plants are diploid with 14 chromosomes, they have 7 pairs of chromosomes (because diploid organisms have two sets of each chromosome).

Step 2: Understanding Gamete Formation

Gametes are formed through meiosis, which results in daughter cells with half the number of chromosomes of the parent cell. Each gamete will thus have 7 chromosomes.

Step 3: Calculate the Number of Unique Combinations

The number of unique combinations of chromosomes that can be produced in gametes is given by the formula 2^n, where n is the number of chromosome pairs. Here, n = 7.

Step 4: Compute the Total Number of Unique Gametes

Using the formula, calculate the total number of unique gametes: \(2^7 = 128\)

Key Concepts

Diploid Organisms

Diploid organisms, like Mendel's pea plants, have two sets of each chromosome. This means each somatic (non-reproductive) cell contains two copies of each chromosome, one from each parent. For example, with 14 chromosomes in total, a diploid pea plant inherits 7 chromosomes from its mother and 7 from its father. This genetic diversity is key to Mendelian genetics, as it sets the basis for understanding how traits are inherited through generations.

Chromosome Pairs

In diploid organisms, chromosomes come in pairs, with each pair containing one chromosome from each parent. These chromosome pairs are crucial in meiosis, as they ensure that gametes receive a diverse set of genetic material. In the case of Mendel's pea plants with 14 chromosomes, there are 7 pairs. Understanding chromosome pairs helps in calculating genetic variations and predicting inheritance patterns in offspring. When figuring out the unique gametes, each pair behaves independently, leading to a variety of genetic combinations.

Meiosis

Meiosis is the process by which diploid organisms produce gametes (like sperm and eggs). It consists of two rounds of division, reducing the chromosome number by half. During meiosis, the chromosome pairs separate, ensuring each gamete has one chromosome from each pair. This means for Mendel's pea plants, with 7 pairs of chromosomes, each resulting gamete will have 7 chromosomes. This segregation of chromosomes during meiosis introduces genetic variation, which is fundamental to understanding Mendel's genetic inheritance.

Gamete Formation

Gamete formation occurs through meiosis, and it results in cells that carry half the number of chromosomes of the parent cell. For instance, in Mendel's pea plants with 14 chromosomes, gametes end up with 7 chromosomes each. The total number of unique gametes is calculated using the formula \( 2^n \), where \( n \) is the number of chromosome pairs. With 7 pairs in pea plants, the number of unique gametes is \( 2^7 = 128 \). This number demonstrates the variety of possible genetic combinations that can result from gamete formation, explaining the genetic diversity seen in offspring.