CAIE A-Level Biology A2 16.2.1 Core Genetic Terms Questions
Define core genetic terms including gene, allele, genotype and phenotype using evidence from each question and mark scheme.
- Syllabus
- 2028–2030
- Course
- Biology 9700
- Level
- A2
Exam points
- Define core genetic terms including gene, allele, genotype and phenotype.
CAIE A-Level Biology A2 16.2.1 Core Genetic Terms Questions question 1
Wing pattern in the butterfly species Heliconius melpomene is controlled by genes on autosomal chromosomes.
The gene for banding pattern on the upper wing has two alleles:
- a dominant allele coding for a full band
- a recessive allele coding for a broken band.
The gene for ray pattern on the lower wing has two alleles:
- a dominant allele coding for rays
- a recessive allele coding for no rays.
Scientists crossed a butterfly that was homozygous dominant for both genes with a butterfly that was homozygous recessive for both genes. The scientists wanted to check whether the phenotypic ratio for offspring in the F2 generation agreed with the expected phenotypic ratio of 9:3:3:1.
The results of this genetic cross are shown in Fig. 4.2.
Fig. 4.2
Explain the term F1 generation.
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