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Edexcel IGCSE Biology 3.25 Monohybrid Cross Probabilities Questions

Work through genetic diagrams and cross results to calculate genotype and phenotype probabilities, including combined sex and trait outcomes.

Syllabus
First assessment 2019
Course
Biology 4BI1

Exam points

  • use a genetic diagram to determine genotype and phenotype ratios and convert a specified offspring outcome into a probability
  • combine sex and phenotype probabilities to calculate the chance of a specified offspring outcome
  • compare observed offspring counts with expected phenotype and sex ratios from a monohybrid cross

Edexcel IGCSE Biology 3.25 Monohybrid Cross Probabilities Questions question 1

[Maximum number: 2]

Fur colour in rats is controlled by a gene with two alleles.

One allele codes for black fur colour. The other allele codes for agouti fur colour.
Several female rats with agouti coloured fur are mated with several male rats with black coloured fur.

All of the offspring have agouti coloured fur.

Calculate the probability of any one offspring from this second cross being male with agouti coloured fur.

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