There are four possible combinations of gametes for the AaBb parent. Half of the gametes get a dominant A and a dominant B allele; the other half of the gametes get a recessive a and a recessive b allele. Both parents produce 25% each of AB, Ab, aB, and ab. Number of gametes = 2n where n= no. of heterozygous pairs of allele AaBb = 22 = 4. These gametes are AB, Ab, aB, ab. 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)

Ratio 1 : 1 : 1 : 1 is ratio of dihybrid test cross. In test cross heterozygous hybrid is crossed with pure recessive plant. RrYy × rryy is correct answer. Answer : (d)

Gametes	RY	Ry	rY	ry
RY	RRYY (round, yellow)	RRYy (round,yellow)	RrYY (round, yellow)	RrYy (round, yellow)
Ry	RRYy (round, yellow)	RRyy (round, green)	RrYy (round, yellow)	Rryy (round, green)
rY	RrYY (round, yellow)	RrYy (round, yellow)	rrYY ( wrinkled, yellow)	rrYy (wrinkled, yellow)
ry	RrYy (round, yellow)	Rryy ( round, green)	rrYy ( wrinkled, yellow)	Rryy (wrinkled, green)

RrYY = 2/16 Answer : (c)

The theory of natural selection was explored by 19th-century naturalist Charles Darwin. Peter D. Mitchell proposed the chemiosmotic hypothesis in 1961. Hill and Bendall proposed the Z scheme. It involves both the photosystem, PS I and PS II. Independent assortment : It states that when two pairs of independent alleles are bought together in F1 hybrid, they show independent dominant effects. in the formation of gametes, law of segregation occurs and the factors assort independently at random. Answer : (a)

Because of sickle shape, sickled cells clump together, especially in the smallest blood vessels, the blood becomes more viscous. The result is slowing of the flow, even greater loss of oxygen from the haemoglobin. Thus the mobility of cell will be different. Answer : (b)

Quantitative inheritance: It is a type of inheritance controlled by more genes in which the dominant alleles have cumulative effect with each dominant allele expressing a part or unit of trait, the full trait being shown only when all the dominant alleles are present. The genes involved are called polygenes. Quantitative inheritance is therefore, also called polygenic inheritance. Polygenic inheritance does not follow Mendelian ratio. Ratio of F2 generation is 1 : 4 : 6 : 4 : 1. Skin colour, human height and eye colour show polygenic inheritance. Option (d) is incorrect because polygenic triat is controlled by multiple gene not multiple alleles. Answer : (a)

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 : (a)

Hereditary sickle cell anaemia is an example of pleiotropy. This 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 Answer : (b)

Hybrid vigour or heterosis is the superiority of hybrid over either of its parents in one or more traits. Answer : (c)

Emasculation is used for the prevention of self-fertilisation. There is the removal of male (pollen) parts of a plant which basically involves the anthers. This helps to perform controlled pollination and breeding purposes. Answer : (c)

Organisms containing two different alleles or individual containing both dominant and recessive gene of an allelic pair is called heterozygous. Answer : (a)

There is no dominant-recessive relationship and thus the hybrid is intermediate of both the parent. This phenomenon is called incomplete dominance. Answer : (b)

When there is a gene existing in more than two allelic forms, this condition is referred to as multiple allelism. Blood group inheritance is controlled by multiple alleles. Answer : (c)

Gametes	BR	Br	bR	br
BR	BBRR	BBRr	BbRR	BbRr
Br	BBRr	BBrr	BbRr	Bbrr
bR	BbRR	BbRr	bbRR	bbRr
br	BbRr	Bbrr	bbRr	bbrr

Since the genes are on different chromosomes, law of independent assortment will be followed BBRR when crossed with bbrr, progeny of genotype BbRr is produced. BbRr × BbRr Heterozygous for both gene = 4/16= 25% Answer : (a)

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 : (d)

	IA	IB
IA	IAIA (A blood group)	IAIB (AB blood group)
IO	IAIO (A blood group)	IBIO (B blood group)

O blood group is not possible. 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 : (a)

Hybridisation is the process of crossbreeding between genetically dissimilar parents to produce a hybrid. Because garden pea is self-fertilizing, the anthers need to be removed before maturity. The process of removal of anthers is called emasculation. Answer : (d)

Priniciple of independent assortment is applicable to only those factors or genes which are present on different chromosomes. The seven characters that Mendel choose were present on 14 chromosomes and so they did not show linkage but if present on 12 chromosomes they would have shown linkage and the principle of independent assortment would not have been discovered. Answer : (b)

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 : (c)

A phenomenon in which two organisms with two pairs of traits or contrasting characters are crossed is called a dihybrid cross. In the genotype TtRr, T and R are gametes for dominant traits and t and r are gametes for recessive traits. So it is a true dihybrid condition. Answer : (d)

Polygenes is termed as a gene in which a dominant allele individually produces a slight effect on the phenotype but in the presence of similar other dominant allele controls the quanitative epression of a trait due to cumulative effect. Answer : (a)

Yellow, round : Yellow, wrinkled, : Green, round : Green, wrinkled 9 : 3 : 3 : 1 Yellow wrinkled seeds = 3/16 × 800 = 150 Answer : (d)

During meiosis, position of each chromosome at the midline during metaphase was random, and that there was never a consistent maternal or paternal side of the cell division. Crossing over do take place.Therefore, each chromosome was independent of the other. Thus, when the parent cell separated into gametes, the set of chromosomes in each daughter cell could contain a mixture of the parental traits, but not necessarily the same mixture as in other daughter cells. 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

4 phenotype and 6 genotype Answer : (b)

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 : (c)

Defination of F2 : The second filial(F2) generation, produced by selfing or intercrossing the F1. Selfing of F1 generation flowers gives F2 generation. Answer : (b)

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
2	Dihybrid cross	4	16	4	9	9:3:3:1	2:4:2:1:2:1:1:2:1

Answer : (b)

The law of independent assortment is applicable to only those factors or genes which are present on different chromosomes. Answer : (a)

Gamete	RY	Ry	rY	ry
ry	RrYy	Rryy	rrYy	rryy
ry	RrYy	Rryy	rrYy	rryy

The test cross ratio 1:1:1:1 proves that the F1 hybrid produces four different types of gametes, each one of which is expressed without affecting the other. The four different types of gametes appear side by side. Example: RrYy (round, yellow seed)(F1 generation ) × rryy (Wrinkled, green seed)( recessive plant) F2 generation Round, yellow : Round,green : wrinkled, yellow : wrinkled, green 1 : 1 : 1 : 1 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)

Answer : (c)

IOIO or ii genotype does not produce any sugar polymer on surface on RBCs. Answer : (d)

Recessive trait is expressed in 6.25% of progeny in F2 generation. Out of 16 progeny, only 1 has single comb, white plumage. Thus, recessive traits are single comb and white plumage. Answer : (a)

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
2	Dihybrid cross	4	16	4	9	9:3:3:1	2:4:2:1:2:1:1:2:1

Answer : (a)

Organisms containing two different alleles or individual containing both dominant and recessive gene of an allelic pair is called heterozygous. Answer : (a)

Backcross is a cross of F1 hybrid with either of two parents . Answer : (a)

Gamete	AB	Ab	aB	ab
ab	AaBb	Aabb	aaBb	Aabb
ab	AaBb	Aabb	aaBb	aabb

AaBb × aabb → AaBb : Aabb : aaBb : aabb = 1 : 1 : 1 : 1 Answer : (b)

Characters	Expected ratios	Example
Monohybrid cross	Phenotypic = 3 : 1 Genotypic = 1 :2 : 1	Pisum sativum
Dihybrid cross	Phenotypic = 9:3:3:1	Pisum sativum
Incomplete dominance	1 : 2 : 1	Mirabilis jalapa
Complementary genes	9 : 7	Lathyrus odoratus
Supplementary genes	9 : 3 : 4	Coat colour of mice
Collaborative supplementary genes	9 : 3 : 3 : 1	Poultry birds – comb pattern
Dominant epistasis	12 : 3 : 1	Fruit colour in Curcurbita
Recessive epistasis	9 : 3 : 4	Coat colour in mice/pigmentation in onion bulb
Duplicate genes	15 : 1	Fruit shape in Capsella bursapastoris
Polymeric gene	9 : 6 : 1	Cucurbita pepo
Suppresor gene	13:3	Leaf colour of rice

Answer : (b)

Mendel’s law of segregation: In F1 the dominant phenotype appears, the recessive phenotype is not lost but reappears in F2. This suggested that there is no blending of Mendelian factors in F1, but they stay together and only one is expressed. A gamete may carry either the dominant or recessive factors but not both as we find F1 individuals. The concept of segregation is often called Mendel’s first principle. While a 3:1 ratio in F2 generation of a monohybrid cross suggested that segregation of alleles does take place which can be confirmed by test cross. Answer : (a)

	IA	IO
IA	IAIA (A blood group)	IAIO (A blood group)
IB	IAIB (AB blood group)	IBIO (B blood group)

If a man has heterozygous A blood group, then its genotype would be IAIO. If man has homozygous A blood group, then there will be no progeny of B blood group   IA IA IA IAIA (A blood group) IAIO (A blood group) IB IAIB (AB blood group) IAIB (AB blood group) Answer : (d)

	IA	IO
IO	IAIO (A blood group)	IOIO (O blood group)
IO	IAIO (A blood group)	IOIO (O blood group)

Genotype for O blood group is IOIO. Genotype for A blood is IAIA or IAIO. Each allele is obtained from each parent. So parents Have possible genotype is IAIO and IOIO. Answer : (d)

	IO	IO
IA	IAIO (A blood group)	IAIO (A blood group)
IB	IBIO (B blood group)	IBIO (B blood group)

Inheritance of blood group is an example of multiple alleles. It has three alleles IA, IB and IO or i. In this IA and IB are co-dominant and IO or i is recessive. Answer : (b)

Mendel was lucky in choosing characters which showed complete independent assortment. He only took those traits for his studies which did not show linkage, interaction or incomplete dominance. Answer : (b)

Gametes	TR	Tr	tR	tr
tr	TtRr (tall,red)	Ttrr (tall,white)	ttRr (dwarf,red)	ttrr (dwarf,white)
tr	TtRr (tall,red)	Ttrr (tall,white)	ttRr (dwarf,red)	ttrr (dwarf, white)

Tall plant, red flower (TtRr) × Dwarf plant, white flower (ttrr) → Progeny Tall, red : tall, white : dwarf, red : dwarf,white 1 : 1 : 1 : 1 Answer : (c)

Mendel experimented on garden pea to study inheritance. He studied the inheritance of seven different pairs of contrasting characters in this plant but considered only one pair at a time. Answer : (d)

This ratio shows that red seed does not follow mendelian law. It occurs in polygenic inheritance. Answer : (a)

Phenotypic ratio and genotypic ratio in F2 generation in incomplete dominance is same. The ratio is 1 : 2 : 1 Answer : (a)

Gametes	Pq
pQ	PpQq

Gene P and Q both are needed for normal hearing. A deaf couple has all children with normal hearing. This implies that all Children has dominant P and Q in their genotype. We can also conclude that each parent has one dominant trait of two set of allele, i.e., mother carries dominant homozygous PP and father carries Dominant homozygous QQ or vice-versa. PPqq × ppQQ Answer : (a)