Biology Year 10 (genetics)?

It shows a family tree. The genotypes of the grandparents regarding a recessive genetic mutation (a) that causes a genetic disorder are given. I can't draw it, so I'll describe it. The first grandma is AA and grandpa is Aa. They gave birth to the father. The second grandma is Aa and the grandpa is Aa too. They gave birthe to the mother. The mother and father then gave birth to the child... QUESTION: What percent chance does the child have of inheriting the disorder? Of being a carrier? Of not carrying the mutation at all? Show your work. QUESTION 2: You discover that those with the disorder rarely live beyond 5 years. How does this change the percentages? Show your work. It's one of the homework questions for test revision and I can't do it!

Answers
Draw the family tree and try and work out the genotypes for the mother and father. Only on the mothers side would an individual show a 25% chance of having the disease. You'll see that the father has 50% chance of being a carrier and 50% chance of not carrying the mutation. For their children, one has to consider all the possible crosses; AA, Aa, aa. For the second part of the question consider if a child was to have the disorder and is unlikely to survive to adulthood (sexual maturity) are they likely to have a chance to pass on their faulty genes? If not, explain the reason (which you would need to do to gain full marks for this).
hellouk
05 November 2012
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