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 Please help! Kaplan Genetics Qns  



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  #1

1) Those of U using Kaplan Notes 2010 (green ed) can U pls tell me if the eg. given on Page 394 on RFLP of X linked disease - is there a mistake please? How can the mom not be a carrier? shaking head

2) Next, this is in both blue & green ed: Chapter on Cytogenetics, look at the part talking abt translocation
The eg given on reciprocal & Robertsonian translocation - how come for adjacent segregation, reciprocal yields only 2 types of gamete but Robertsonian yields 4 types? I actually counted there shd be 4 also for the reciprocal translocation!

3) Review qn. on consanguinity Qn. 8 in both green & blue ed:
How did it arrive at 1/64???

Pls help!! Thank U!







  #2

Q 3. In usual conditions two siblings share only 1/2 of their genetic materials. But here, because two siblings have different mothers so probability of male (II-2) and his sister (II-3) share their genetic materials is 1/2 multiply by 1/2 = 1/4.

Probability that in III generation, male and female share their genetic materials
is again 1/2 multiply by 1/2 = 1/4. This is because in each birth, a child inherits 1/2 of his/her genetic materials from either parent.

So, overall chance that the mentioned couple to share their genetics is 1/4 multiply by 1/4 = 1/16. Again this is because the grandfather had two wives. In usual conditions first cousins share 1/8 of their genetics.

Since Q asks about a recessive disorder, there will be 25% (1/4) that a child will get the disease. So 25% (1/4) of 1/16 = 1/64. Note that both parents should have the allele for the disease (share their genetics).

If the grandfather had not married two different women, the chance would be
1/4 of 1/8 = 1/32.

Hope to help


  #3

Hello sir,,,,,,,,I told you.....Q 3. In usual conditions two siblings share only 1/2 of their genetic materials. But here, because two siblings have different mothers so probability of male (II-2) and his sister (II-3) share their genetic materials is 1/2 multiply by 1/2 = 1/4............please help me,,,,,,,,,,,





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