4. The pedigree below depicts the inheritance of a rare...

4. The pedigree below depicts the inheritance of a rare genetic trait in four generations of a family. I 1 2 II 1 2 3 4 5 6 7 III 1 2 3 4 5 6 7 8 9 10 IV 1 2 3 4 5 6 7 A. Assuming complete penetrance and no new mutations, what is the mode of inheritance of the rare disease (your choices are: autosomal dominant, autosomal recessive, and X-linked recessive, X-linked dominant; Y-linked)? (2 points) B. Using correct genetic symbols, give the genotypes of the following individuals. In ambiguous cases, indicate all possible genotypes. (3 points; 1 pt each) III-2 ______ III-9 ______ IV-3 ______ C. If individuals IV-4 and IV-5 marry, what is the probability that their first child could be a male with the genetic disorder? (2 points)

Transcript

00:01 Hello everyone, in this question we have been given the pedigree chart.

00:05 So, in the first question it says that assuming complete penetrance and no new mutation, what is the mode of inheritance of the rare disease? so, basically here we can see that there is skip of generation and the pattern here is the crisscross inheritance.

00:25 As here we can see that in the first generation the male is completely normal and the female is also normal, but in the next generation the male child are infected.

00:40 That means here the female must have been a carrier for the disease.

00:45 Then only it is possible that the male child here is infected and there can be the normal male child, the carrier female can be there and the normal female child.

00:58 So, that is why these male are infected.

01:01 So, that is why here this is the x -linked recessive inheritance.

01:08 So, an affected male has an unaffected daughter who in turn has an affected son.

01:17 So, this is considered as a crisscross inheritance and the trait is more common in males than the female and there is no male to male transmission.

01:28 The trait is the skip of generation.

01:31 Then in the next question it says using correct genetic symbols give the genotypes of the following individuals.

01:38 So, here the first one is 3 -2.

01:42 So, the 3 -2 here is the normal female who married the normal male, but we can see that one of her son is infected.

01:52 That means here the female genotype is this.

01:57 She must have been the carrier for the disease because her father and the son are affected.

02:03 Then we have been asked about 3 -9.

02:06 So, 3 -9 here is affected.

02:09 Here we can see that the father and mother of both the father and mother of 3 and 9 are normal.

02:18 That means the mother must have been the carrier and that is why here the genotype is this...

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