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AQA Biology B2 (Exam on 10th June)

6 Marker Predictions for the AQA exam tomorrow?
Reply 1
Avatar for HarryGCSE
HarryGCSE
OP
10
I'm thinking a Meiosis and Mitosis comparison question
Reply 2
Avatar for harry42
harry42
2
Praying for speciation but my teacher was thinking comparing the structure of different cells or mitosis meiosis
structure of cells or specialised cells might come up. i doubt meiosis and mitosis because it doesnt ask for heavy detail on the spec but it might.
Reply 4
Avatar for F3rnw3h
F3rnw3h
13
Cadasil.pngCould someone explain this please? Not sure if I'm just looking at it wrong, but couldn't the fact that the affected parents have unaffected children also show that CADASIL could be caused by a recessive allele?

1.What is the evidence in the diagram that CADASIL is caused by a dominant allele?
2 affected parents have unaffected child or 1 and 2 5 / 6 or if recessive all of 1 and 2’s children would have CADASIL
2. Person 7 has CADASIL.Is person 7 homozygous or heterozygous for the CADASIL allele?Give evidence for your answer from the diagram.
heterozygous – has unaffected children or because if homozygous all children would have CADASIL
I haven't done any revision on B3.. And I've never looked at the textbook so basically al year 11 I was just messing about, idk what to do is it possible to learn all of it in 3 hours :/
Reply 6
Avatar for Benb2000
Benb2000
2
Original post by Tasha_140
Cadasil.pngCould someone explain this please? Not sure if I'm just looking at it wrong, but couldn't the fact that the affected parents have unaffected children also show that CADASIL could be caused by a recessive allele?

1.What is the evidence in the diagram that CADASIL is caused by a dominant allele?
2 affected parents have unaffected child or 1 and 2 5 / 6 or if recessive all of 1 and 2’s children would have CADASIL
2. Person 7 has CADASIL.Is person 7 homozygous or heterozygous for the CADASIL allele?Give evidence for your answer from the diagram.
heterozygous – has unaffected children or because if homozygous all children would have CADASIL


I don't get this either, surely if two affected parents had a child all the children would be affected as it is dominant allele? Someone clarify?
Reply 7
Avatar for eks85
eks85
2
Original post by thatnerdygirl001
I haven't done any revision on B3.. And I've never looked at the textbook so basically al year 11 I was just messing about, idk what to do is it possible to learn all of it in 3 hours :/


Yeah just put your mind to it . There's really good resources online . .. cgp ... And look at past papers check you can do it along mark scheme
Reply 8
Avatar for eks85
eks85
2
Original post by Benb2000
I don't get this either, surely if two affected parents had a child all the children would be affected as it is dominant allele? Someone clarify?


No because if it was a recessive allele that caused it both mum would be rr and dad would be rr.. Therfore if you do the punnet square you will see that for it was recessive allele it would be 100% for all children . The fact that some children got it and others don't means it would have to be dD dD
(edited 7 years ago)

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