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12th Standard CBSE Biology Principles of Inheritance and Variation
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Q:

(a) Haemophilia is a sex-linked recessive disease. Study the pedigree analysis given below showing the inheritance of the disease in a family and answer the questions that follows:


(i) Give the evidence from the above analysis, which suggests that the disease is (1) sex-linked and (2) caused by a recessive allele.
(ii) Write the possible genotypes of the individual '2' and '5'.
(b) Why is thalassemia categorised as a Mendelian disorder? State the condition when an individual will suffer from the disease.

Accepted Solution

A:

(a) (L) 1. It has occurred in males; since the male receives the X-chromosome from the female parent, the genemust
be sex-linked, i.e. present on X-chromosome.
2. Since the disease is not shown by the female parent, it must be caused by a recessive allele; the female has two X-chromosomes and the disease to appear; she
must be homozygous recessive.
(ii) Individual 2  - \(XX^{ h }\)
  5-    \(X^{ h }y\)
(b) Thalassemia is caused by a mutation of the allele or its deletion; it is passed on to the progeny in the same lines as the traits studied by Mendel in pea plants.
 It is an autosomal, recessively inherited disorder, transmitted to the progeny, when both the parents are heterozygous i.e. carrier of the disease.
The offspring who is homozygous recessive suffers from the disease.

Dear Students Great you got the answer for your question,

(a) Haemophilia is a sex-linked recessive disease. Study the pedigree analysis given below showing the inheritance of the disease in a family and answer the questions that follows:


(i) Give the evidence from the above analysis, which suggests that the disease is (1) sex-linked and (2) caused by a recessive allele.
(ii) Write the possible genotypes of the individual '2' and '5'.
(b) Why is thalassemia categorised as a Mendelian disorder? State the condition when an individual will suffer from the disease.

Read - Related Few More Questions and answers for your reference & knowledge


In 12th Standard CBSE Biology Subject Principles of Inheritance and Variation


write a percentage of the pea plants that would be homozygous recessive in the F2 generation, when tall F1 heterozygous pea plats are selfed.

In a test cross progeny of pea plats, all were bearing violet flowers. Give the genotypes of the parent pea plants.

A garden pea plant produced axial white flowers. Another of the same spcies produced terminal violet flowers. Identify the dominant traits

Name the respective pattern of inheritance where F1 phenotype
(a) does not resemble either of the two parents and is in between the two.
(b) resembles only one of the two parents.

In a dihybird cross, when would the propoetion of parential gane combinations be much higher than non-parential types, as experimently shown by morgan and his group

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