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Inheritance And Variation Mcq
Quiz 2
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Q.1
Most favourite and ideal material for research in genetics is ... .. [ AMU 2000 ]
0%
a) Housefly
0%
b) Mosquito
0%
c) Frog
0%
d) Fruit fly
Explanation
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)
Q.2
A plant having 24 cm long internodes is crossed with a plant having 12 cm long internodes. The hybrids have 18 cm long internodes due to ... .. [KCET 2002]
0%
a) Multiple alleles
0%
b) Complete dominance
0%
c) Recessive dominance
0%
d) Incomplete dominance
Explanation
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)
Q.3
Which of the following cross determines heterozygosity or homozygosity .... .. [ Tamil nadu 2001 ]
0%
a) Monohybrid cross
0%
b) Dihybrid cross
0%
c) Test cross
0%
d) Back cross
Explanation
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)
Q.4
When pure long plant having white flower is crossed with pure dwarf plant having red flower, the dwarf progeny in F2 generation is ... ... [ RPMT 2006 ]
0%
a) 1/16
0%
b) 3/16
0%
c) 4/16
0%
d) 9/16
Explanation
- -
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)
Q.5
Ultimate source of variation is ... .. [ DPMT 2001]
0%
a) Fertilization
0%
b) Mitosis
0%
c) Meiosis
0%
d) Mutations
Explanation
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)
Q.6
Inheritance of ABO blood groups is an example of ... .. [ JKCMEE 2008]
0%
a) Incomplete dominance
0%
b) Dominance
0%
c) Codominance
0%
d) Both B and C
Explanation
Answer : (d)
Q.7
In test cross, the individual is crossed with ... ... [ BHU 1993 ]
0%
a) Homozygous dominant individual
0%
b) Heterozygous individual
0%
c) Homozygous recessive
0%
d) None of the above
Explanation
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)
Q.8
The process of mating between closely related individuals is ... ... [CBSE 1994 ]
0%
a) Self breeding
0%
b) Inbreeding
0%
c) Hybridization
0%
d) Heterosis
Explanation
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)
Q.9
Both alleles express in hetrozygote when they are ... .. [ AMU 2012 ]
0%
a) Recessive
0%
b) Lethals
0%
c) Semidominant
0%
d) Codominant
Explanation
Co-dominance: It is the phenomenon of two alleles lacking dominant-recessive relationship and both expressing themselves in the organism. Answer : (d)
Q.10
In heterozygous condition, both the alleles express in ... .. [ EAMCET 2008]
0%
a) Colour blindness
0%
b) AB blood group
0%
c) Rh factor
0%
d) A and B factor
Explanation
Blood type (phenotype)
Genotype
Antigen
Antibodies
A
I
A
I
A
or I
A
I
O
A
b
B
I
B
I
B
or I
B
I
O
B
a
AB
I
A
I
B
Both A and B
Neither a nor b
O
I
O
I
O
Neither A nor B
Both a and b
ABO blood group is example of co-dominance. Answer : (b)
Q.11
In Mirabilis/ Antirrhinum, hybrid between red and white flowered plants is pink flowered. This is ... ... [ RPMT 1990 ]
0%
a) Heterosis
0%
b) Segregation
0%
c) Incomplete dominance
0%
d) Dominance
Explanation
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)
Q.12
For finding the different types of gametes produced by genotype AaBb, it should be crossed with genotype.. .... [ CBSE 2005 ]
0%
a) AABB
0%
b) aabb
0%
c) AaBb
0%
d) aaBB
Explanation
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)
Q.13
Math the columns and choose the correct combination
(a) Monohybrid cross
(p) T and t
(b) Test cross
(q) TT
(c) Alleles
(r) Tt ×Tt
(d) Homozygous tall
(s) tt
-- --
(t) Tt × tt
0%
a) a - r; b - t; c - s; d - q
0%
b) a - t; b - r; c - q; d - s
0%
c) a - r; b - t; c - p; d - q
0%
d) a - r; b - p; c - t; d - q
Explanation
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)
Q.14
Two individuals with similar external appearance but different generic make up have the similar ... .. [ AMU 1999 ]
0%
a) Genotype
0%
b) Phenotype
0%
c) Heterozygote
0%
d) Homozygote
Explanation
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)
Q.15
Medel's law of independent assortment can be demonstrated by ... ... [ CPMT 1993 ]
0%
a) Test cross
0%
b) back cross
0%
c) Monohybrid cross
0%
d) Dihybrid cross
Explanation
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)
Q.16
out of seven characters in Pea plant studied by Mendel, the number of flower based characters was ... ... [AMU 2009 ]
0%
a) 1
0%
b) 3
0%
c) 4
0%
d) 2
Explanation
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)
Q.17
Both husband and wife have normal vision though their father were colour blind and mother without any allele for colour blindness. the probability of their daughters becoming colour blind is ... .. [ KCET 2009]
0%
a) 0%
0%
b) 15%
0%
c) 25%
0%
d) 50%
Explanation
Gametes
X
Y
X
c
X
c
X (carrier girl)
X
c
Y (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)
Q.18
During meiosis all alleles of a genic pair segregate from each other. How many alleles are passed onto a gamete ... ..[ kerala 2011 ]
0%
a) One
0%
b) Two
0%
c) Four
0%
d) Six
Explanation
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)
Q.19
When both the parents are of blood group AB, children would be of blood group ... .. [ kerala 2003 ]
0%
a) A, B, AB and O
0%
b) A, B and AB
0%
c) A and B
0%
d) A, AB and O
Explanation
I
A
I
B
I
A
I
A
I
A
(A blood group)
I
A
I
B
(AB blood group)
I
B
I
A
I
B
(AB blood group)
I
B
I
B
(B blood group)
Genotype of blood group AB is IAIB Answer : (b)
Q.20
Independent assortment can be deduced from ... .. [ RPMT 2005 ]
0%
a) Monohybrid cross
0%
b) Test cross
0%
c) Back cross
0%
d) Dihybrid cross
Explanation
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)
Q.21
on Q407) Number of linkage groups in human male, female and pea plant respectively are:
0%
a) 23, 23, 14.
0%
b) 24, 23, 14.
0%
c) 24, 23, 7.
0%
d) 23, 24, 7.
Explanation
Answer:(c)
Q.22
Assertion : HbSHBS is homozygous condition of sickle cell anaemia Reason: It occurs due to substitution of glutamic acid by valine at sixth position in β-chain of haemoglobin
0%
a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion
0%
b) The Assertion and Reason are true but Reason is not correct explanation of Assertion
0%
c) Assertion is true but, Reason is false
0%
d) Assertion is false but, Reason is true
Explanation
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)
Q.23
Heterozygosity/ dominance of phenotype can be determined by ... .. [ Odisha 2010 ]
0%
a) Back cross
0%
b) Test cross
0%
c) Reciprocal cross
0%
d) Hybrid cross
Explanation
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)
Q.24
Genotypic ratio of a dihybrid cross is ... .. [ RPMT 1998 ]
0%
a) 12:3:1
0%
b) 15:1
0%
c) 1:2:1
0%
d) 1:2:2:4:1:2:1:2:1
Explanation
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)
Q.25
Cross AABb × aaBb yield AaBB : AaBb : Aabb : aabb offspring in the ratio of ... ... [ BHU 1994 ]
0%
a) 0:3:1:1
0%
b) 1:2:1:0
0%
c) 1:1:1:1
0%
d) 1:2:1:1
Explanation
Answer : (b)
Q.26
Grain colour of wheat is determined by three pairs of polygenes. What proportion of F2 progeny will resemble either parents following a cross of AABBCC ( dark colour) with aabbcc ( light colour) ... ... [ AIIMS 2005 ]
0%
a) None
0%
b) Half
0%
c) Less than 5%
0%
d) One third
Explanation
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)
Q.27
Sexual reproduction brings about ... .. [ CPMT 2002 ]
0%
a) polyploidy
0%
b) Aneuploidy
0%
c) Euploidy
0%
d) Genetic recombination
Explanation
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)
Q.28
Which one of the following traits of Garden Pea studied by Mendel was a recessive feature? ... .. [ CBSE 2003 ]
0%
a) Axial flower position
0%
b) Green seed colour
0%
c) Green pod colour
0%
d) Round seed shape
Explanation
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)
Q.29
Heterozygous round yellow seeded plants are self crossed. Round green offspring shall be represented by genotype .... ... [ kerala 2011]
0%
a) RrYy, RrYY, RRYr
0%
b) Rryy, RRyy, rryy
0%
c) rrYy, rrYY
0%
d) Rryy, RRyy
Explanation
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)
Q.30
ABO blood grouping in humans is an example of .... [ HPPMT 2011 ]
0%
a) polygenic inheritance
0%
b) Multiple alleles
0%
c) Incomplete dominance
0%
d) Epistasis
Explanation
ABO blood grouping is an example of dominance, codominance and multiple alleles. Answer : (b)
Q.31
Pleiotropic effect is found in ... ... [ AMU 2001]
0%
a) Human skin colour
0%
b) Night blindness
0%
c) Haemophilia
0%
d) Sickle cell anaemia
Explanation
Answer : (d)
Q.32
Two pea plants were subjected to cross pollination. Of the 183 plants produced in next generation, 94 plants were tall and 89 plants were dwarf. the genotypes of the two parental plants are likely to be ... ... [ KCET 2006 ]
0%
a) TT × tt
0%
b) Tt × Tt
0%
c) Tt × tt
0%
d) TT × TT
Explanation
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)
Q.33
If red eyed ( dominant) fly is mated with white eyed ( recessive) fly, the ratio of red to white eyed in F2 generation would be .... .. [ CPMT 1996 ]
0%
a) 3 : 1
0%
b) 2 : 2
0%
c) 2 : 1
0%
d) 1 : 3
Explanation
No. of traits (n)
Experiment
Types of gametes (2
n
)
No. of offsprings (gametes)
2
No. of phenotype (2
n
)
No. of genotype (3
n
)
Phenotypic ratio
Genotypic ratio
1
Monohybrid cross
2
4
2
3
3:1
1:2:1
Answer : (a)
Q.34
The contrasting pair of factors in Mendelian cross are called ... .. [ CBSE 1991 ]
0%
a) Multiple alleles
0%
b) Allelomorphs
0%
c) Alloloci
0%
d) Paramorphs
Explanation
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)
Q.35
Albinism is due to nonsynthesis of melanin on account of absence of ... .. [ BHU 1999 ]
0%
a) Melanase
0%
b) Luciferase
0%
c) Tyrosinase
0%
d) Lysine
Explanation
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)
Q.36
Mendel's law of segregation is applicable to ... .. [ Wardha 2005]
0%
a) Dihybrid cross only
0%
b) Both dihybrid and monohybrid crosses
0%
c) Monohybrid cross only
0%
d) Dihybrid but not monohybrid cross
Explanation
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)
Q.37
In a cross of red and white flowered Snapdragon, F1 plants will have flowers ... .. [ MPPMT 1997 ]
0%
a) Red
0%
b) White
0%
c) Both A and B
0%
d) Pink
Explanation
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)
Q.38
Human blood grouping ABO instead of ABC because O in it refers to ... .. [ CBSE 2009 ]
0%
a) No antigen A or B on RBCs
0%
b) Other antigens besides A and B
0%
c) Over dominance of its gene over A and B
0%
d) One antibody only either anti-A or anti-B
Explanation
Blood type (phenotype)
Genotype
Antigen
Antibodies
A
I
A
I
A
or I
A
I
O
A
b
B
I
B
I
B
or I
B
I
O
B
a
AB
I
A
I
B
Both A and B
Neither a nor b
O
I
O
I
O
Neither A nor B
Both a and b
Answer : (a)
Q.39
Mendel's work was got republished in 'Flora' by ... .. [AMU 2003 ]
0%
a) De vries
0%
b) Tschermak
0%
c) Correns
0%
d) All the above
Explanation
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)
Q.40
Among seven pairs of traits studied by Mendel, the number of traits related to flower, pod and seed were .... [ AMU 2012]
0%
a) 2, 2, 2
0%
b) 2, 2, 1
0%
c) 1, 2, 2
0%
d) 1, 1, 2
Explanation
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)
Q.41
Genes controlling seven traits in Pea studied by Mendel were actually located on .... .. [ B.H.U 1994 ]
0%
a) Seven chromosomes
0%
b) Six chromosomes
0%
c) Four chromosomes
0%
d) Five chromosomes
Explanation
Mendel when experimenting on garden peas choose 7 characters. These were present on four chromosomes- 1, 4, 5 and 7. Answer : (c)
Q.42
In a plygenic cross aa Bb Cc × Aa Bb Cc the phenotypic ratio of offspring is 1:6:'X':20:'X':6:What is the value of 'X' .... .. [ DPMT 2011 ]
0%
a) 3
0%
b) 7
0%
c) 15
0%
d) 25
Explanation
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)
Q.43
ABO blood group system is due to .... ... [ CBSE 1990 ]
0%
a) Multifactor inheritance
0%
b) Incomplete dominance
0%
c) Multiple alleles
0%
d) Epistasis
Explanation
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)
Q.44
"Gametes are never hybrid". It is a statement of law of ... .. [ AIIMS 2000 ]
0%
a) Dominance
0%
b) Segregation
0%
c) Independent assortment
0%
d) Random fertilisation
Explanation
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)
Q.45
Percentage of heterozygous individuals obtained from selfing of Rr individuals is ... .. [ AIIMS 1992 ]
0%
a) 100
0%
b) 75
0%
c) 50
0%
d) 25
Explanation
RR and rr are homozygous. Out of four progeny, 2 are homozygous and 2 are heterozygous. That implies, 50% are heterozygous. Answer : (c)
Q.46
In a dihybrid cross between RRYY and rryy the number of RrYy F2 genotype will be ... ... [ JKCMEE 2008]
0%
a) 4
0%
b) 3
0%
c) 2
0%
d) 9
Explanation
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)
Q.47
Test cross is used to check ... .. [ CPMT 2010 ]
0%
a) Heterozygosity in F1 generation
0%
b) Independent assortment
0%
c) Heterozygosity in F2 generation
0%
d) Segregation
Explanation
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)
Q.48
What is the number of alleles for blood group in an individual ... ... [ JKCET 2012 ]
0%
a) 1
0%
b) 2
0%
c) 3
0%
d) 4
Explanation
Each person possess any two of the three ‘I’ gene alleles. Answer : (b)
Q.49
Pure red flowered and white flowered plants were crossed. it produced 120 offspring with ... .. [ AMU 1998 ]
0%
a) 90 white - flowered and 30 red-flowered
0%
b) 90 red -flowered and 30 white flowered
0%
c) 60 red flowered and 60 white flowered
0%
d) All red flowered
Explanation
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)
Q.50
R is dominant red flower trait while r is recessive white flower trait. heterozygous Rr (red) is crossed with homozygous red flowered plant. 64 offspring are produced. Number of white flowered plants is ... .. [ DPMT2001]
0%
a) 64
0%
b) 32
0%
c) 16
0%
d) 0
Explanation
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)
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