Gce Model Questions Vol1 2022 Biology Question 10

Practice essay / theory question 10 from the 2022 Gce Model Questions Vol1 Biology examination. This question covers Mendelian Genetics, Linkage and Recombination, Dihybrid Crosses, Epistasis .

Gce Model Questions Vol1 2022 Biology Essay / Theory
Topics: Mendelian Genetics Linkage and Recombination Dihybrid Crosses Epistasis
Question 10 GCE_MODEL_QUESTIONS_VOL1 • 2022 • BIOLOGY • essay

A researcher is studying inheritance of flower colour and plant height in a diploid flowering plant. Flower colour is controlled by a single gene with alleles R (red) dominant to r (white). Plant height is controlled by a second gene with alleles T (tall) dominant to t (short). The two genes are located on the same chromosome and are 10 map units apart.

Question Parts

( a )
Define the terms genotype and phenotype, and give an example of each for the two traits under study.
( b )
The researcher crosses a heterozygous tall red plant (RrTt) with a homozygous short white plant (rrtt). Assuming independent assortment, calculate the expected phenotypic ratio of the F1 generation.
( c )
Because the genes are linked, the observed F1 phenotypic ratio deviates from the expected. A test cross of an F1 individual (heterozygous for both genes) with a double‑recessive (rrtt) yields 400 progeny with the following phenotypes: 120 red‑tall, 80 red‑short, 80 white‑tall, 120 white‑short. Calculate the recombination frequency and the map distance between the two genes. Discuss what the result indicates about linkage.
( d )
Explain how epistasis could modify the phenotypic ratios in a dihybrid cross involving these two genes, providing a specific example of a possible epistatic interaction.

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About This Question

This is Gce Model Questions Vol1 2022 Biology Question 10. It is one of the essay questions from the 2022 Gce Model Questions Vol1 Biology examination.

The question covers Mendelian Genetics, Linkage and Recombination, Dihybrid Crosses, Epistasis .

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