COMMAND WORD · BIOLOGY
Draw the conclusion that the printed information allows, and do not import one it does not force.
Given A, so B.
Original question
An illustrative family has an affected father, an unaffected mother and affected sons. The allele is X-linked recessive. Deduce the mother’s genotype.
Annotated answer
ASons receive their X chromosome from the mother. She is unaffected, but she has affected sons. SoShe passed on the allele and also has a working allele. BHer genotype is heterozygous.
The labels match the frame. Read them in order. This is one accurate route, not the only one.
If the conclusion needs a fact the question did not give, it is not yet a deduction.
Writing “it might be genetic” and never stating the genotype.
Original practice
Mark points shown after marking
The diagram shows DNA profiles from a mother, her child and two men, A and B.
Deduce which man could be the child’s father, from this profile alone.
(1)State one thing that you cannot claim from this profile.
(1)Total for this question: 2 marks
Man A can be the father on this profile because the child’s second band matches him and not man B. The profile does not describe anything else about either man. This is an illustrative profile, not a case.
