Principles of Inheritance & Variation Test - 3

A cross between two individuals, one with AB blood group and the other with A blood group will producefour genotypes and three phenotypes.

The genotypes of a husband and wife are  I^A I^B  and  I^A i.
Four different possible genotypes of their  children are : I^A I^B , I^A i, I^B i, I^A I^A

The possible number of phenotypes of their  children are:

• Blood group A (I^A I^A , I^A i)
• Blood group B (I^B i)
• Blood group AB (IAIB)

Fig : Cross between blood groups AB and A  
Hence, the correct option is B.
NCERT Reference: Topic    Co-dominance ”of chapter  "Principles of Inheritance and Variation "   of NCERT  

• Polygenic/Quantitative inheritance:  Controlling a character by two or more genes is called Multi factor inheritance.
  Example: Inheritance of skin colour of human beings.
• Mendelian Inheritance:  The transfer of traits from one generation into another into the next generation in the form of a particulate structure is called Mendelian Inheritance.
  Example: Cross based on height or colour and shape of seeds.
• Monogenic inheritance: It is also called the Monohybrid cross. Cross between a homozygous dominant parent and a homozygous recessive parent on the basis of a single character.
  Example: Cross based on the height of the pea plants.
• Complementary genes:  Two independent pairs of genes, which interact to produce a trait together, but each dominant gene alone does not show its effect, are called complementary genes.
  Example: Cross based on the colour of flowers in Sweet potato.

Hence, the correct option is B.

NCERT Reference: Topic  POLYGENIC INHERITANCE ”of chapter   "Principles of Inheritance and Variation "  of NCERT  

• Co-dominance is the phenomenon that deviates from Mendel ’s law of inheritance.
• Both the alleles appear in offspring instead of one as in Mendel ’s experiment.
• ABO blood grouping in human beings is an example of co-dominance in which both I^A and I^B appear simultaneously to form AB blood type.

Hence, the correct option is D.

NCERT Reference:  Topic - Co-dominance ”of chapter  "Principles of Inheritance and Variation "  of NCERT  

• If the genotype is AaBb the alleles that are  produced will be AB, Ab, aB, ab, since there are two diallelic characters in the genotypes the person must be heterozygous for both genes. AABB is homozygous. So, the correct answer is "AaBb ".

Fig : Diallelic characters in the genotype

Hence, the correct option is B.

NCERT Reference: Topic - INHERITANCE OF TWO GENES ”of chapter  "Principles of Inheritance and Variation "   of NCERT  

• F1 pink flowered plants are heterozygous. When selfing is done the genotype and phenotype develops as 1:2:1 as 40 red, 80 pink and 40 white flowering plants.  It is called Incomplete dominance .
• The appearance of a new phenotype in the progeny but not either of the parents is called Incomplete dominance.

Fig : Cross showing incomplete dominance in Mirabilis jalapa

Hence, the correct option is C.
NCERT Reference: Topic-   Incomplete Dominance ”of chapter  "Principles of Inheritance and Variation "  of NCERT.

• In Snapdragon flower, cross between true-breeding white and red coloured flower produce pink coloured flower in the F1 generation.
• This happens due to the incomplete dominance of alleles over the other.

Hence, the correct option is A.
NCERT Reference:  Topic - Incomplete Dominance of chapter  "Principles of Inheritance and Variation "  of NCERT.

• People who are colour blind fail to distinguish between red and green colours.
• Colour blindness is a sex-linked recessive trait in which the normal gene and its recessive allele are carried by X-chromosome.

Hence, the correct option is A.

NCERT Reference:  Topic- Mendelian Disorders of chapter  "Principles of Inheritance and Variation "  of NCERT. 

• Plotting of specific genes on the chromosome is known as chromosomes map or linkage map or genetic map .
• It shows the position of genes on chromosome in respect to others.

Fig: Chromosome Map

Hence, the correct option is D.
NCERT Reference:  Topic Linkage and Recombination of chapter  "Principles of Inheritance and Variation "  of NCERT. 

• When two genes are situated very close to one another on the chromosome, hardly any cross-over is produced.
• Such genes are called linkage and do not separate from each other during gamete formation.

Hence, the correct option is A.

NCERT Reference: Topic-  Linkage and Recombination of chapter  "Principles of Inheritance and Variation "  of NCERT. 

Sex chromosomes of human beings are heteromorphic as they are of different size. Y chromosome is smaller than X chromosome in size.

Hence, the correct option is D.
NCERT Reference:  Topic- SEX DETERMINATION of chapter  "Principles of Inheritance and Variation "  of NCERT.