Biology 9700 · AS & A Level · Passage of information from parents to offspring
Passage of information from parents to offspring — practice question
MELAS syndrome is an inherited disorder caused by a mutation in a gene within mitochondrial DNA (mtDNA). Every mtDNA molecule is inherited from the mother. Fig. 6.1 depicts four generations of a family in which several members have MELAS syndrome.
(a)[4]
With reference to Fig. 6.1, state and explain the evidence that MELAS syndrome is an mtDNA disease rather than a disorder caused by a mutation in a gene on the X chromosome.
(b)[3]
Studying mtDNA can reveal how recently species have diverged from one another. Describe the features of mtDNA that make it suitable for investigating evolution.
Worked solution & mark scheme
This 7-mark question has a full step-by-step worked solution and mark scheme. One marking point: “MELAS is not transmitted by affected males” …