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A couple has two sons and two daughters. Only one son is colour blind and the rest of the siblings are normal. Assuming colour blindness is sex-linked, which ONE of the following would be the phenotype of the parents?

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Important Questions on Principles of Inheritance and Variation

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Which of the following most appropriately describes haemophilia?
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Which of the following muscular disorders is inherited?
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Pick out the correct statements:
(i) Haemophilia is a sex-linked recessive disease.
(ii) Down's syndrome is due to aneuploidy.
(iii) Phenylketonuria is an autosomal recessive gene disorder.
(iv) Sickle cell anaemia is an X-linked recessive gene disorder.
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Conditions of a karyotype 2n±1 and 2n±2 are called
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The genetic disorder in which an individual has an overall masculine development, gynaecomastia and is sterile:
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Statement (S): The heterozygous individuals for sickle-cell anaemia HbAHbS express disease phenotype and also carriers of the disease.

Reason (R): HbAHbS genotype individuals are resistant to severe effects of malaria.

The correct answer is

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If a colour-blind man marries a woman who is homozygous for normal colour vision, the probability of their son being colour-blind is
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Thalassemia and sickle cell anaemia are caused due to a problem in globin molecule synthesis. Select the correct statement.
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Point mutation is caused in which of the following diseases?
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A colourblind man marries a woman with normal sight who has no history of colour blindness in her family. What is the probability of their sons being colourblind?
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In an Organism, mutation in a single gene exhibits multiple phenotypic expression. Identify the underlying genetic mechanism in the above instance.
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A man whose father was colour blind marries a woman who had a colour blind mother and normal father. What percentage of male children of this couple will be colour blind?
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A change of single base pair in the gene for beta globin chain (in human haemoglobin) that results in the change of amino acid residue glutamine to valine which is due to
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Both male and female have normal vision though their fathers were colour-blind, and mothers did not have any gene for colour blindness. The probability of their daughter becoming colour-blind is
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Which one of the following conditions is not responsible for the presence of deoxygenated blood in the arteries of a newborn?
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A disease caused by an autosomal primary non-disjunction is
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An abnormal human baby with 'XXX' sex chromosomes was born due to:
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In the following human pedigree, the filled symbols represents the affected individuals. Identify the type of given pedigree.


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