A couple with normal vision bear a colour blind child. Work out a cross to show how it is possible and mention the sex of the affected child. - Biology


A couple with normal vision bear a colour blind child. Work out a cross to show how it is possible and mention the sex of the affected child.



Colour blindness is an X-linked recessive disease.


Male:  XY - Normal
         XcY - Colour-blind

Female: XX - Normal
            XcX - Carrier
            XcXc - Colour blind

According to the given situation, both the parents are normal but the child is colour blind. This means that the male parent is normal and the female parent is the carrier. The cross can be represented as follows:
Parents        XY      ☓      XcX
Gametes      X,Y             Xc,X

Offsprings    XcX    XX     XcY    XY

Result: 50% sons are colour blind.
Thus, the affected child will be male.

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2015-2016 (March) Delhi Set 2

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Identify 'a', 'b', 'c',’d’, 'e' and 'f' in the table given below:

No. Syndrome Cause Characteristics of  affected individuals Sex
1. Down's Trisomy of 21 'a' (i)
2. 'c' XXY Overall masculine
3. Turner's 45 with XO 'e' (i)

Mention any two autosomal genetic disorders with their symptoms.

In which of the following disorders number of chromosomes present is 47?
(A) Turner’s syndrome
(B) Cushing’s syndrome
(C) Acquired Immuno - Deficiency Syndrome
(D) Down’s syndrome

Name the disorder caused by under secretion of thyroxine in children

During a medical investigation, an infant was found to possess an extra  chromosome-21. Describe the symptoms the child is likely to develop later in the life.

The genotype of a person withTumer's syndrome will be:
(i)   44+XXY
(ii)  44+XYY
(iii) 44+XO
(iv) 44+XXYY

State any two symptoms of Down’s syndrome.

What do sex linked traits appear in males than in females? 

Very Short Answer Question.

Give an example of a chromosomal disorder caused due to nondisjunction of autosomes.

In human beings 45 chromosomes/single X/XO abnormality causes ______.

Webbed neck is characteristic of ______ syndrome.

Give a detail account of thalassemia.

Mention the symptoms of Phenylketonuria.

A male rabbit of genotype 'AABBDDEE' is crossed with a female rabbit of genotype 'aabbddee' to produce F1 hybrid offspring. How many genetically different gametes can be produced by this F1 hybrid?

Feminised males have ______ chromosomes.

Identify the INCORRECT statement.

Identify I and II in the given diagram of chromosome.

Thalassemia and sickle cell anaemia are caused due to a problem in globin molecule synthesis. Identify the correct statement from the following.

Identify the disease caused by an autosomal primary non-disjunction.

In Klinefelter syndrome, an extra chromosome is a result of non-disjunction of X-chromosome during ____________.

Following list indicates various genetic diseases. Identify the diseases that are not caused due to single gene defect.

Huntington's chorea, alkaptonuria, Sickle cell anaemia, Down syndrome, thalassemia, Taysachs disease, Turner syndrome, cystic fibrosis, haemophi Lia, Klinefelter syndrome, albinism

Choose the correct option which appropriately classifies the following disorders into Mendelian and chromosomal disorders:

Colour blindness, Down syndrome, Sickle cell anaemia, Turner syndrome, Thalassemia, Haemophilia, Phenylketonuria, Klinefelter syndrome.

Sickel-cell anaemia is an example of ______.

It is well known that Queen Victoria of England was a carrier for haemophilia. Since this is an X-linked disease, it can be predicted that ______.

Extra chromosome ‘X’ is present in which one of the following cases?

The person with Turner’s syndrome has ______.

Mental retardation in man associated with sex chromosomal abnormality is usually due to ______.

A person with 47 chromosomes due to an additional Y-chromosome suffers from a condition called ______.

Select the incorrect statement regarding pedigree analysis.

Which of the following is called as Royal disease?

Clotting of blood is to ______.

The practice of analyzing inheritance patterns in human beings is called ______

The technique exployed in human genetic counselling is:

If a father and son are both defective in red-green colour vision, is it likely that the son inherited the trait from his father? Comment.

In Down's syndrome, karyotyping has shown that the disorder is associated with trisomy of chromosome number 21 usually due to ______.

Why is thalassemia cotegorised as a Mendelian disorder? Write the symptoms and explain the causes of the disease. How does it differ from Sickle cell anaemia?

What is the genotype of Turner's Syndrome?

Mention any one symptom of Turner's syndrome.

What are chromosomal disorders?


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