Figure 12 shows some characteristics of pea plants - Edexcel - GCSE Biology - Question 6 - 2023 - Paper 1

The completed Punnett square will have the following values:

|   wrinkled seeds  |   r   |   r   |
|------------------|-------|-------|
|   R              |   Rr  |   Rr  |
|   r              |   rr   |   rr   |

Here, R represents the allele for round seeds and r represents the allele for wrinkled seeds.

From the completed Punnett square, 50% of the offspring (2 out of 4) will produce round seeds. Therefore, the percentage is 50%.

To calculate the ratio, we take the number of plants with purple flowers (133) and divide it by the number of plants with white flowers (46).

This can be calculated as:

y = rac{133}{46} ightarrow y ext{ (approximately 2.89)}

Rounding gives us a ratio of 3:1.

It was possible for this cross to produce offspring with white flowers because both parents are heterozygous (Pp) for flower color, meaning they each carry one allele for purple flowers and one allele for white flowers. This results in a possibility for some offspring to inherit two recessive alleles (pp) leading to white flowers.

Pea plant cells are diploid and have a total of 14 chromosomes. During meiosis, gametes are produced and go through a division process that halves the number of chromosomes. Therefore, each gamete has half the number of chromosomes, which is 7.

During fertilisation, a male gamete (pollen) fuses with a female gamete (ovule) to form a zygote. This zygote then develops into a seed, containing genetic material from both parents, which ultimately leads to the formation of a new plant.