Principles of Inheritance and Variation

The recessive genes located on X-chromosomes in humans are always -

1. Expressed in females
2. Sub-lethal
3. Expressed in males
4. Lethal

After a mutation at a genetic locus the character of an organism changes due to the change in :-

1. Protein synthesis pattern
2. RNA transcription pattern
3. DNA replication
4. Protein structure

In a mutational event, when adenine is replaced by guanine, it is a case of -

1. Frameshift mutation
2. Transition
3. Transversion
4. Transcription

Which one of the following traits of garden pea studied by Mendel was a recessive feature?

1. Green seed colour
2. Green pod colour
3. Axial flower position
4. Round seed shape

The genes controlling the seven pea characters studied by Mendel are now known to be located on how many different chromosomes?

1. Six
2. Seven
3. Five
4. Four

Two crosses between the same pair of genotypes or phenotypes in which the sources of the gametes are reversed in one cross, is known as:

1. Reciprocal cross
2. Reverse cross
3. Test cross
4. Dihybrid cross

Pattern baldness, moustaches and beard in human males are examples of:

1. Sex limited traits
2. Sex influenced traits
3. Sex determining traits
4. Sex linked traits

Which one of the following conditions though harmful in itself, is also a potential saviour from a mosquito borne infectious disease?

1. Pernicious anaemia
2. Thalassaemia
3. Leukemia
4. Sickle cell anaemia

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