Principles of Inheritance and Variation

Down's syndrome is caused by an extra copy of chromosome number 21. What percentage of offspring produced by an affected mother and a normal father would be affected by this disorder?

1. 50%
2. 100%
3. 75%
4. 25%

In Drosophila, the sex is determined by:

1. X and Y chromosomes
2. Whether the egg is fertilized or develops parthenogenetically
3. The ratio of number of X-chromosomes to the sets of autosomes
4. The ratio of pairs of X-chromosomes to the pairs of autosomes

Christmas disease is another name for :-

1. Hepatitis B
2. Sleeping sickness
3. Haemophilia B
4. Down's syndrome

Which of the following is the example of pleiotropy ?

1. Thalassemia
2. Haemophilia
3. Sickle cell anaemia
4. Colour blindness

There are three genes a, b and c. The percentage of crossing over between a and b is 20%, b and c is 28% and a and c is 8%. What is the sequence of genes on chromosome?

1. a, b, c
2. b, a, c
3. a, c, b
4. None

On selfing a plant of F1 generation with genotype “AABbCC”, the phenotypic ratio in F2 generation will be

1. 1 : 1
2. 3 : 1
3. 9 : 3 : 3 : 1
4. 27 : 9 : 9 : 9 : 3 : 3 : 3 : 1

A gene is said to be dominant if : -

1. It is expressed only in heterozygous condition
2. It expresses its effect only in homozygous stage
3. It is never expressed in any condition
4. It is expressed both in homozygous and heterozygous condition

A diseased man marries a normal woman. They get three daughters and five sons. All the daughters were diseased and sons were normal. The gene of this disease is : -

1. Sex linked dominant
2. Autosomal dominant
3. Sex linked recessive
4. Sex limited character

Which of the following is a correct match -

1. Sickle cell anaemia = X – Chromosome
2. Down Syndrome = 21st Chromosome
3. Haemophilia = Y – Chromosome
4. Parkinson Disease = X & Y Chromosome

Change in sequence of nucleotide in DNA is called as -

1. Recombination
2. Mutation
3. Mutagen
4. Translation