This biology question covers important biological concepts and processes. The step-by-step explanation below helps you understand the underlying mechanisms and reasoning.
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4.3.1 The parents are homozygous. 4.3.2 Each parent has two identical alleles for the trait (RR for red, WW for white). 4.3.3 a) The phenotypic ratio of the F2-generation is 1 Red : 2 Pink : 1 White. b) The percentage of red offspring is 25%. 4.4.1 The genetic phenomenon is environmental influence on phenotype (or phenotypic plasticity). 4.4.2 Environmental influence on phenotype is when the expression of a genotype is modified by environmental factors, leading to different phenotypes from the same genotype. 4.4.3 THREE environmental factors that may have contributed to the difference in height of the maize plants: • Water availability • Soil nutrients • Light intensity • Temperature 4.4.4 The scientific term for this improvement is hybrid vigour (or heterosis). 4.4.5 The type of breeding system is cross-breeding (or hybridization). 4.5.1 Polygenic inheritance is a type of inheritance where a single phenotypic trait is controlled by two or more genes, and each gene contributes additively to the phenotype. 4.5.2 Step 1: Identify the number of additive alleles in the AABB genotype. The genotype AABB has 4 dominant alleles (A, A, B, B). Step 2: Calculate the height contributed by the additive alleles. Each additive allele contributes 10 cm. Contribution from additive alleles = 4 alleles × 10 cm/allele = 40 cm. Step 3: Calculate the total height. The base height for a recessive plant (aabb) is 30 cm. Total height = Base height + Contribution from additive alleles Total height = 30 cm + 40 cm = 70 cm. The height of an AABB tomato plant is 70 cm. 4.5.3 Step 1: Determine the required number of additive alleles for a 50 cm plant. Base height = 30 cm. Desired height = 50 cm. Additional height needed = 50 cm - 30 cm = 20 cm. Since each additive allele contributes 10 cm, the number of additive alleles required is 20 cm / 10 cm/allele = 2 additive alleles. Step 2: List genotypes with exactly two dominant (additive) alleles. The genes are controlled by two pairs of genes (A/a and B/b). The THREE different genotypes of a 50 cm tomato plant are: • AAbb • aaBB • AaBb Last free one today — make it count tomorrow, or type /upgrade for unlimited.