Principles of Inheritance and Variation

Down's syndrome in humans is due to :

1. Three 'X' chromosomes
2. Monosomy
3. Three copies of chromosome 21
4. Two 'Y' chromosomes

Represented below is the inheritance pattern of a certain type of traits in humans. Which one of the following conditions could be an example of this pattern ? [figure]

1. Haemophilia
2. Sickle cell anaemia
3. Thalassemia
4. Phenylketonuria

A test cross is carried out to :

1. Determine whether two species or varieties will breed successfully
2. Determine the genotype of a plant at F2
3. Predict whether two traits are linked
4. Assess the number of alleles of a gene

Which one of the following is a wrong statement regarding mutations ?

1. UV and gamma rays are mutagens
2. Deletion and insertion of base pairs cause frame-shift mutations
3. Cancer cells commonly show chromosomal aberrations
4. Change in a single base pair of DNA does not cause mutation

A normal-visioned man whose father was colour-blind, marries a woman whose father was also colour-blind. They have their first child as a daughter. What are the chances that this child would be colour-blind ?

1. 50%
2. 25%
3. 100%
4. Zero percent

F2 generation in a Mendelian cross showed that both genotypic and phenotypic ratios are same as 1 : 2 : 1. It represents a case of

1. Monohybrid cross with incomplete dominance
2. Co-dominance
3. Monohybrid cross with complete dominance
4. Dihybrid cross

Which one of the following conditions of the zygotic cell would lead to the birth of a normal human female child?

1. only one Y chromosome
2. only one X chromosome
3. one X and one Y chromosome
4. two X chromosomes

Test cross in plants or in Drosophila involves crossing:

1. the F1 hybrid with a double recessive genotype
2. between two genotypes with dominant trait
3. between two F1 hybrids
4. between two genotypes with recessive trait

Which one of the following conditions correctly describes the manner of determining the sex ?

1. XO condition in humans as found in Turner Syndrome, determines female sex
2. XO type of sex chromosomes determine male sex in grasshopper
3. Homozygous sex chromosomes (ZZ) determine female sex in Birds
4. Homozygous sex chromosomes (XX) produce male in Drosophila

Mutations can be induced with :

1. Gamma radiation
2. Infra Red radiations
3. IAA
4. Ethylene