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Figure 12 shows some characteristics of pea plants - Edexcel - GCSE Biology - Question 6 - 2023 - Paper 1
Question 6
Figure 12 shows some characteristics of pea plants. | flower colour | seed shape | |---------------|---------------| | purple | round | | white ... show full transcript
Worked Solution & Example Answer:Figure 12 shows some characteristics of pea plants - Edexcel - GCSE Biology - Question 6 - 2023 - Paper 1
Step 1
Which term describes the allele for white flowers?
Answer
The term that describes the allele for white flowers is 'recessive.' In genetics, a recessive allele is one that is masked by the presence of a dominant allele. Since purple flowers are dominant to white, the allele for white flowers is recessive.
Step 3
State the percentage of the offspring that will produce round seeds.
Answer
To determine the percentage of offspring producing round seeds, we can analyze the completed Punnett square:
- Rr (round seeds)
- Rr (round seeds)
- rr (wrinkled seeds)
The ratio of round seeds to total offspring is 2:1, which means:
The percentage of offspring producing round seeds can be calculated as follows:
ext{Percentage} = rac{2}{3} imes 100 = 66.67\%
Rounding gives approximately 67%.
Step 4
Step 5
Explain why it was possible for this cross to produce some offspring with white flowers.
Answer
This cross could produce some offspring with white flowers because both parent plants are heterozygous (i.e., Pp). This means that each parent carries one allele for purple flowers and one for white flowers. Therefore, some offspring can inherit the combination pp (two recessive alleles), resulting in white flowers.
Step 6
Explain why pea plant gametes have only seven chromosomes.
Answer
Pea plant cells are diploid, meaning they contain two sets of chromosomes (i.e., 14 chromosomes in total). During meiosis, gametes are produced, and this process reduces the chromosome number by half, resulting in haploid gametes that contain only seven chromosomes.
Step 7
Describe what happens at fertilisation.
Answer
During fertilization, a male gamete (pollen) fuses with a female gamete (ovule) to form a zygote. This fusion restores the diploid number of chromosomes, resulting in a new organism that inherits genetic material from both parent plants. The zygote then undergoes development to form a new pea plant.