D. melanogaster only has four pairs of chromosomes compared to 23 pairs in humans. This allow researchers to maintain complex stocks with multiple mutations on single chromosomes over generations. Their short life cycle and large number of offspring are also advantageous for genetic research because new fly lines are quick and easy to make Answer : (d)

A plant hybrid of 24 cm long internode and 12 cm internodes has 18 cm internodes. The length of internode of hybrid is intermediate as neither of them is dominant. This phenomenon is known as incomplete dominance. Answer : (d)

Crossing of F1 individual having dominant phenotype with its homozygous recessive parents is called test cross. The test cross is used to determine whether the individuals exhibiting dominant characters are homozygous or heterozygous. Answer : (c)

- -	TW	Tw	tW;	tw
TW	TTWW Tall, White	TTWw Tall, White	TtWW Tall, White	TtWw Tall, Red
Tw	TTWw Tall, White	TTww Tall, Red	TtWw Tall, White	Ttww Tall, Red
tW	TtWW Tall, White	TtWw Tall, White	ttWW Dwarf, White	ttWw Dwarf, White
tw	TtWw Tall, White	Ttww Tall, Red	ttWw Dwarf, White	ttww Dwarf, Red

Pure long plant having white flower (TTWW) is crossed with pure dwarf plant having red flower (ttww) produces F1 generation of long plants having white flowers with genotype TtWw. F1 generation when selfed produces the following F2 generation. TtWw × TtWw Thus, dwarf progeny in F2 generation= 4/16.Hence the correct answer is option ‘C’. Answer : (c)

Variation are differences in morphological, physiological, cytological and behavioristic trait of individuals belonging to same species. Mutation is a phenomenon which results in alteration of DNA sequences and consequently results in changes in the genotype and the phenotype of an organism. In addition to recombination, mutation is another phenomenon that leads to variation in DNA. Answer : (d)

Answer : (d)

Crossing of F1 individual having dominant phenotype with its homozygous recessive parents is called test cross. The test cross is used to determine whether the individuals exhibiting dominant characters are homozygous or heterozygous. Answer : (c)

Inbreeding is process of the mating of individuals or organisms that are closely related through common ancestry Hybrid vigour or heterosis is the superiority of hybrid over either of its parents in one or more traits. Answer : (b)

Co-dominance: It is the phenomenon of two alleles lacking dominant-recessive relationship and both expressing themselves in the organism. Answer : (d)

Blood type (phenotype)	Genotype	Antigen	Antibodies
A	IAIA or IAIO	A	b
B	IBIB or IBIO	B	a
AB	IAIB	Both A and B	Neither a nor b
O	IOIO	Neither A nor B	Both a and b

ABO blood group is example of co-dominance. Answer : (b)

In Mirabilis / Antirrhinum, hybrid is intermediate of both the parents. This occurs when neither of the alleles being dominant. This phenomenon is called incomplete dominance. Answer : (c)

Crossing of F1 individual having dominant phenotype with its homozygous recessive parents is called test cross. The test cross is used to determine whether the individuals exhibiting dominant characters are homozygous or heterozygous. Homozygous recessive parents is aabb. Answer : (b)

Homozygous tall: It means organism have two similar genes or alleles. Example TT. Test cross: Crossing of F1 individual having dominant phenotype with its homozygous recessive parents is called test cross . Tt × tt Allele: A pair of contrasting trait is called allele. Example T and t for height, G and g for colour of pod. Monohybrid cross involves one trait. It can be TT × tt OR Tt × Tt Answer : (c)

Genotype is sum total of heredity or genetic make up. Phenotype is the external feature of organism. Heterozygous refers to having inherited different forms of a particular gene from each parent. A heterozygous genotype stands in contrast to a homozygous genotype, where an individual inherits identical forms of a particular gene from each parent. Answer : (b)

Law of segregation and law of dominance is demonstrated by monohybrid cross. Segregation of alleles can be confirmed by test cross. Law of independent assortment is demonstrated by dihybrid cross Answer : (c)

Mendel studied seven character of garden peas. These are plant height, flower position, pod colour, pod shape, flower colour, seed colour and seed shape. Out of these 2 are flower based i.e., Flower position and flower colour. Answer : (d)

Gametes	X	Y
Xc	XcX (carrier girl)	XcY (diseased boy)
X	XX (normal girl)	XY (normal boy)

Colour blindness is a sex linked recessive disorder. This defect is due to mutation in certain genes present in the X chromosome. It occurs in about 8 per cent of males and only about 0.4 per cent of females. Mostly women are carrier of gene. They are colour blind only when her mother is carrier and father is colour blind. In the above case, man has colour blind father. Thus man is normal with genotype XY. Woman has colour blind father. This means she is carrier of gene with genotype XcX XY × XcX One of the girl will be normal and another will be carrier but none of them is colourblind. Answer : (a)

Law of segregation is based on the fact that the alleles do not show any blending and that both the characters are recovered as such in the F2 generation though one of these is not seen at the F1 stage. Though the parents contain two alleles during gamete formation, the factors or alleles of a pair segregate from each other such that a gamete receives only one of the two factors. Answer : (a)

	IA	IB
IA	IAIA (A blood group)	IAIB (AB blood group)
IB	IAIB (AB blood group)	IBIB (B blood group)

Genotype of blood group AB is IAIB Answer : (b)

Law of segregation and law of dominance is demonstrated by monohybrid cross. Segregation of alleles can be confirmed by test cross. Law of independent assortment is demonstrated by dihybrid cross Answer : (d)

Answer:(c)

Sickle-cell anaemia is an autosome linked recessive trait that can be transmitted from parents to the offspring when both the partners are carrier for the gene (or heterozygous). The disease is controlled by a single pair of allele, HbA and HbS . Out of the three possible genotypes only homozygous individuals for HbS (HbSHbS ) show the diseased phenotype. Sickle cell anemia is caused by the substitution of Glutamic acid (Glu) by Valine (Val) at the sixth position of the beta globin chain of the haemoglobin molecule. The substitution of amino acid in the globin protein results due to the single base substitution at the sixth codon of the beta globin gene from GAG to GUG. The mutant haemoglobin molecule undergoes polymerisation under low oxygen tension causing the change in the shape of the RBC from biconcave disc to elongated sickle like structure. Answer : (b)

Crossing of F1 individual having dominant phenotype with its homozygous recessive parents is called test cross. The test cross is used to determine whether the individuals exhibiting dominant characters are homozygous or heterozygous. Answer : (b)

Dihybrid cross involves two traits. Genotypic ratio can be figured out by the formula (1 : 2 : 1)n where n = number of traits. (1 : 2 : 1)2 = 1 : 2 : 2 : 4 : 1 : 2 : 1 : 2 : 1 Answer : (d)

Answer : (b)

Polygene results in quantitative inheritance which is characterised by occurrence of intermediate forms between the parental type. In case of crossing between AABBCC (dark colour) and aabbcc (light colour) in F2 generation seven phenotypes will obtain with ratio of 1:6:15:20:15:6:1. The total number of progeny is 64, out of which only two will be likely resemble with either parents. Hence, their proportion in F2 generation would be 3.12 i.e., less than 5% Answer : (c)

During sexual reproduction, the genetic material of two individuals is combined to produce genetically-diverse offspring that differ from their parents. This increase genetic recombination. The genetic diversity of sexually-produced offspring is thought to give species a better chance of surviving in an unpredictable or changing environment. Answer : (d)

Traits	Dominant	Recessive
Plant height	Tall (1.2 – 2.0m)(T)	Dwarf (0.25 – 0.5m) (t)
Flower position	Axillary (A)	Terminal (a)
Pod colour	Green (G) or (Y)	Yellow (g) or (y)
Pod shape	Full or inflated (I) or (C)	Constricted (i) or (c)
Flower colour	Violet (V) or (W)	White (v) or (w)
Seed shape	Round (R) or (W)	Wrinkled (r) or (w)
Seed colour	Yellow (Y) or (G)	Green (y) or (g)

Answer : (b)

In Heterozygous allele plant, character of dominant trait is expressed. Thus, round is dominant over wrinkled and yellow is dominant over green. For the round green offsprings, allele for green will be yy and round can be either Rr or RR. Therefore genotype of round, green is Rryy, RRyy Answer : (d)

ABO blood grouping is an example of dominance, codominance and multiple alleles. Answer : (b)

Answer : (d)

94 plants are tall and 89 plants are dwarf. The ratio of tall and dwarf is almost 1 : 1. This is possible when genotype of individual expressing dominant trait is heterozygous and it is crossed with recessive trait plant. Answer : (c)

No. of traits (n)	Experiment	Types of gametes (2n)	No. of offsprings (gametes)2	No. of phenotype (2n)	No. of genotype (3n)	Phenotypic ratio	Genotypic ratio
1	Monohybrid cross	2	4	2	3	3:1	1:2:1

Answer : (a)

Mendel's Law of Independent Assortment states the inheritance of one pair of factors ( genes ) is independent of the inheritance of the other pair. contrasting pair of factors means differing strikingly. A pair of contrasting characters is called allelomorphs or allele. Answer : (b)

Albinism results from inheritance of recessive gene alleles and is known to affect all vertebrates, including humans. It is due to absence or defect of tyrosinase, a copper-containing enzyme involved in the production of melanin. Tyrosinase synthesizes melanin from the amino acid tyrosine. Absence of this enzymes causes albinism. Answer : (c)

Law of segregation applies to diploid organism that form gametes to reproduce sexually. The law only applies to traits controlled exclusively by a single gene pair in which one of the two alleles is dominant over other. This is true in both monohybrid cross and dihybrid cross. Answer : (b)

Snapdragon shows incomplete dominance. Neither red flower allele nor white flower allele is dominant and thus intermediate hybrid is obtained. F1 plants will have pink colour flower. Answer : (d)

Blood type (phenotype)	Genotype	Antigen	Antibodies
A	IAIA or IAIO	A	b
B	IBIB or IBIO	B	a
AB	IAIB	Both A and B	Neither a nor b
O	IOIO	Neither A nor B	Both a and b

Answer : (a)

Three botanists - Hugo DeVries, Carl Correns and Erich von Tschermak - independently rediscovered Mendel's work in the same year. They named the laws as Mendel’s laws of inheritance and got it published in “Flora” in 1901. Thus, the correct option is D. Three botanists - Hugo DeVries, Carl Correns and Erich von Tschermak - independently rediscovered Mendel's work in the same year. They named the laws as Mendel’s laws of inheritance and got it published in “Flora” in 1901. The three Europeans, unknown to each other, were working on different plant hybrids when they each worked out the laws of inheritance. When they reviewed the literature before publishing their own results, they were startled to find Mendel's old papers spelling out those laws in detail. Each man announced Mendel's discoveries and his own work as confirmation of them. Thus, the correct option is D. Answer : (d)

Traits	Dominant	Recessive
Plant height	Tall (1.2 – 2.0m)(T)	Dwarf (0.25 – 0.5m) (t)
Flower position	Axillary (A)	Terminal (a)
Pod colour	Green (G) or (Y)	Yellow (g) or (y)
Pod shape	Full or inflated (I) or (C)	Constricted (i) or (c)
Flower colour	Violet (V) or (W)	White (v) or (w)
Seed shape	Round (R) or (W)	Wrinkled (r) or (w)
Seed colour	Yellow (Y) or (G)	Green (y) or (g)

2 related to flower i.e., flower position and flower colour. 2 related to pod i.e., pod shape and pod colour. 2 related to seed i.e., seed shape and seed colour. 1 related to height. Answer : (a)

Mendel when experimenting on garden peas choose 7 characters. These were present on four chromosomes- 1, 4, 5 and 7. Answer : (c)

Polygene results in quantitative inheritance which is characterised by occurrence of intermediate forms between the parental type. In case of crossing between AABBCC (dark colour) and aabbcc (light colour) in F2 generation seven phenotypes will obtain with ratio of 1:6:15:20:15:6:1. Answer : (c)

Inheritance of ABO blood group is an example of dominance, codominance and multiple allele. Co-dominance because In ABO both allele expresses themselves in the organism. Multiple alleles because blood group is determined by combination of three alleles IA, IB and IO or i. Dominance because blood group is determined by antigen types. Answer : (c)

The gametes which are formed are always pure for a particular character. A gamete may carry either dominant or recessive factor but not both. This is why it is called ‘principle of segregation’ or ‘law of purity of gametes’. Answer : (b)

RR and rr are homozygous. Out of four progeny, 2 are homozygous and 2 are heterozygous. That implies, 50% are heterozygous. Answer : (c)

Gametes	RY	Ry	rY	ry
RY	RRYY	RRYy	RrYY	RrYy
Ry	RRYy	RRyy	RrYy	Rryy
rY	RrYY	RrYy	rrYY	rrYy
ry	RrYy	Rryy	rrYy	rryy

F2 generation Answer : (a)

Crossing of F1 individual having dominant phenotype with its homozygous recessive parents is called test cross. The test cross is used to determine whether the individuals exhibiting dominant characters are homozygous or heterozygous. Answer : (a)

Each person possess any two of the three ‘I’ gene alleles. Answer : (b)

One allele is dominant over other. In F1 generation the dominant phenotype appears, the recessive reappears in F2 generation. Since red is dominant over white, all 120 offspring produces will be plants having red flower. Answer : (d)

Gametes	R	R
R	RR	RR
r	Rr	Rr

Above question is an example of back cross. Backcross is a cross of F1 hybrid with either of two parents. In this case, F1 hybrid is crossed with dominant parent. All the F2 offsprings develop dominant character. Rr (heterozygous red flowered plant) × RR ( homozygous red flowered plant) F2 generation All the offsprings are red flowered plants with 50% homozygous and 50% heterozygous. Thus there are no white coloured flower. Answer : (d)