Biology 9700 · AS & A Level · Passage of information from parents to offspring

Passage of information from parents to offspring — practice question

In humans, the ABO blood grouping system is controlled by one gene with $I^A$, $I^B$ and $I^O$.
(a)[4]

State the difference between the terms gene and allele.

(b)[4]

Fig. 7.1 contains a pedigree diagram showing the inheritance of the ABO blood group system. The blood group of some individuals is already shown in the pedigree. Use the details in Fig. 7.1 together with the genetic symbols $I^A$, $I^B$ and $I^O$, to complete the table for individuals 1, 2, 3 and 4 by stating each phenotype and genotype.

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This 8-mark question has a full step-by-step worked solution and mark scheme. One marking point: “a gene is a stretch / sequence of DNA that codes for a polypeptide” …

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