Principles of Inheritance and Variation · Question 98

ABO blood groups in humans are controlled by the gene I. It has three alleles – IA, IB and i. Since there are three different alleles, six different genotypes are possible. How many phenotypes can occur –

1. One
2. Two
3. Three
4. Four

Select the correct statement from the ones given below with respect to dihybrid cross –

1. Genes far apart on the same chromosome show very few recombinations
2. Tightly linked genes on the same chromosome show very few recombinations
3. Tightly linked genes on the same chromosome show higher recombinations
4. Genes loosely linked on the same chromosome show similar recombinations as the tightly linked ones

The genotype of a plant showing the dominant phenotype can be determined by –

1. Pedigree analysis
2. Back cross
3. Test cross
4. Dihybrid cross

Which one of the following cannot be explained on the basis of Mendel's Law of Dominance?

1. Out of one pair of factors one is dominant, and the other recessive
2. Alleles do not show any blending and both the characters recover as such in F2 generation
3. The discrete unit controlling a particular character is called a factor
4. Factors occur in pairs

Select the incorrect statement from the following:

1. Baldness is a sex limited trait
2. Galactosemia is an inborn error of metabolism
3. Linkage is an exception to the principle of independent assortment in heredity
4. Small population size results in random genetic drift in a population

Sickle-cell anaemia is:

1. Caused by substitution of valine by glutamic acid in the beta globin chain of haemoglobin
2. An autosomal linked dominant trait
3. Caused by a change in a single base pair of DNA
4. Characterised by elongated sickle like RBCs with a nucleus

The most popularly known blood grouping is the ABO grouping. It is named ABO and not ABC, because "O" in it refers to having:

1. Other antigens besides A and B on RBCs
2. No antigens A and B on RBCs
3. Overdominance of this type on the genes for A and B types
4. One antibody only – either anti-A or anti-B on the RBCs

Study the pedigree chart given below: [figure] What does it show?

1. Inheritance of a recessive sex-linked disease like haemophilia
2. Inheritance of a sex-linked inborn error of metabolism like phenylketonuria
3. The pedigree chart is wrong as this is not possible
4. Inheritance of a condition like phenylketonuria as an autosomal recessive trait

Which one of the following conditions in humans is correctly matched with its chromosomal abnormality/linkage?

1. Klinefelter's syndrome — 44 autosomes + XXY
2. Colour-blindness — Y-linked
3. Down syndrome — 44 autosomes + XO
4. Erythroblastosis foetalis — X-linked

Haploids are more suitable for mutation studies than the diploids. This is because:

1. all mutations, whether dominant or recessive are expressed in haploids
2. mutagens penetrate in haploids more effectively than in diploids
3. haploids are reproductively more stable than diploids
4. haploids are more abundant in nature than diploids