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NEET Biology MCQ
Inheritance And Variation Mcq
Quiz 10
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Q.1
ion Q53) The allele which is unable to express its effect in the presence of another is called
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a) Co - dominant
0%
b) Supplementary
0%
c) Complementary
0%
d) Recessive
Explanation
Recessive allele is the factor of an allele pair which is unable to express its effect in the presence of its constrasting factor in a heterozygote. Example t in Tt. Answer:(d)
Q.2
ion Q54) Linkage is
0%
a) directly related to crossing over
0%
b) same as translocation
0%
c) inversely related to crossing over
0%
d) opposite to segregation
Explanation
Linkage and crossing over is alternative to each other because linkage is the tendency of genes to stay together during transmission, whereas crossing over is exchange of segments of homologous chromosomes which results in variation Answer:(c)
Q.3
ion Q55) Which disease results from the genetic inability to synthesize a single enzyme?
0%
a) Diabetes
0%
b) Phenylketonuria
0%
c) Colour-blindness
0%
d) Down's syndrome
Explanation
Phenylketonuria : This inborn error of metabolism is also inherited as the autosomal recessive trait. The affected individual lacks an enzyme that converts the amino acid phenylalanine into tyrosine. As a result of this phenylalanine is accumulated and converted into phenylpyruvic acid and other derivatives. Accumulation of these in brain results in mental retardation. These are also excreted through urine because of its poor absorption by kidney Answer:(b)
Q.4
ion Q56) In the case of co-dominance, the F1 generation resembles:
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a) Dominant parent
0%
b) Recessive parent
0%
c) Both the parents
0%
d) None of the parents
Explanation
Co-dominance is a phenomenon where there is no dominant-recessive relationship and both the trait are expressed in the progeny. Answer:(c)
Q.5
ion Q57) Which one from those given below is the period of Mendel's hybridisation experiments?
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a) 1856 - 1863
0%
b) 1840 - 1850
0%
c) 1857 - 1869
0%
d) 1870 - 1877
Explanation
From 1856 to 1865, Mendel conducted breeding experiments on garden peas (Pisum sativum) in the garden of his monastery. Answer:(a) Answer:(a)
Q.6
ion Q58) A normal-visioned man whose father was colour-blind marries a woman whose father was also a colour-blind. They have their first child as a daughter. What are the chances that this child would be colour-blind?
0%
a) 100%
0%
b) 0%
0%
c) 25%
0%
d) 50%
Explanation
Gametes
X
Y
X
c
X
c
X (carrier daughter)
X
c
Y ( colour blind son)
X
XX (normal daughter)
XY (normal son)
Colour Blindness : It is a sex-linked recessive disorder due to defect in either red or green cone of eye resulting in failure to discriminate between red and green colour. This defect is due to mutation in certain genes present in the X chromosome. The man has normal vision, so his genotype will XY. Woman has colour blind father. This makes her a carrier of the disease with genotype as XCX. Answer:(b)
Q.7
ion Q59) A pure breeding pea plant with the dominant phenotype of character A and recessive phenotype of character B was crossed with another pure breeding plant with the recessive phenotype of character A and dominant phenotype character B. Offspring of this cross was crossed with a homozygous recessive for both the characters A and B. The following results were obtained. 22 were phenotypically dominant of A and recessive of B 4 were phenotypically recessive for both A and B 22 were phenotypically recessive for A and dominant for B. The results show that
0%
a) genes A and B are linked
0%
b) independent segregation of genes A and B
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c) Mendelian dihybrid inheritance
0%
d) polygenic inheritance.
Explanation
Equal number of phenotypically dominant A and recessive B offspring and phenotypically recessice A and dominant B showcase that segregation and assortment of alleles of both character is independent. The result follows law of independent assortment seen in dihybrid cross. Answer:(c)
Q.8
ion Q60) Grain colour in wheat is determined by three pairs of polygenes. Following the cross AABBCC (dark colour) X aabbcc (light colour), in F2 generation what proportion of the progeny is likely to resemble either parent?
0%
a) None
0%
b) Less than 5 percent
0%
c) One third
0%
d) Half
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:(b)
Q.9
ion Q61) Which of the following does not contribute to Mendel’s success?
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a) Large sampling size
0%
b) Statistical analysis
0%
c) Performed experiments on single variety of pea
0%
d) Performed experiments on successive generations
Explanation
From 1856 to 1865, Mendel conducted breeding experiments on garden peas (Pisum sativum) in the garden of his monastery. His breeding materials consisted of pure lines. Unlike his predecessors who worked on large number of characters simultaneously, Mendel worked with one or few pairs of traits at one time. He kept record of every cross and subsequent generations produced through self breeding. Thus he maintained statistical records of all the experiments and analysed them carefully. Different varieties of pure breeding pea had contrasting expression of traits like height, color of flower, position of flower etc. Mendel only chose those characters which showed consistent results. He started with 34 varieties, reduced the number to 22 but worked only on 7. Answer:(c)
Q.10
ion Q62) Which among the following is not correct about incomplete/imperfect linkage?
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a) According to the pattern of cross proposed by T.H. Morgan parental offspring are produced always more in number along with a few recombinants
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b) The two genes linked on the same chromosomes are away from each other. So that they can be separated by crossing over.
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c) Incomplete linkage is reported regarding all pairs of gene in Drosophila.
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d) The dihybrid cross containing two characters eye colour and shape of wings show incomplete linkage.
Explanation
• The linked genes which are widely located in chromosomes and have chances of separation by crossing over are called incompletely linked genes and the phenomenon of their inheritance is called incomplete linkage. • The linked genes do not always stay together because homologous non-sister chromatids may exchange segments of varying length with one another during meiotic prophase. This sort of exchange of chromosomal segments in between homologous chromosomes is known as crossing over. Example. The incomplete linkage has been reported in female Drosophila and various other organisms such as tomato, maize, pea, mice, poultry and man, etc. Answer:(c)
Q.11
ion Q63) Recessive character is expressed in
0%
a) F0
0%
b) F1
0%
c) F2
0%
d) Never expressed.
Explanation
Recessive character is always expressed in F2 character. Answer:(c)
Q.12
ion Q64) Consider the following statement and find out the incorrect one:
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a) Advancement in Microscopy made the study of chromosomal behaviour possible.
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b) The two alleles of a gene pair are located on homologous site on homologous chromosomes.
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c) Experimental verification of chromosomal theory of Inheritance was done by T. H. Morgan et. Al.
0%
d) Morgan Chose Drosophila as an experimental animal because it has variations that can be seen with high power of microscope.
Explanation
Two allelic genes are located on two homologous chromosomes. Experimental Verification of the Chromosomal Theory of Inheritance was done by Thomas Hunt Morgan and his colleagues. Morgan carried out various dihybrid crosses in Drosophila, with the genes that were sex-linked, i.e., the genes are present on the X-chromosome. . Morgan decided to use fruit flies to study how physical traits (for example, eye color) were transmitted from parents to offspring, and he was able to elegantly show that genes are stored in chromosomes and form the basis of heredity. . Answer:(d)
Q.13
ion Q66) Mental retardation is associated with
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a) Klinefelter’s syndrome
0%
b) Haemophilia
0%
c) Cystic fibrosis
0%
d) Phenylketonuria
Explanation
Phenylketonuria : This inborn error of metabolism is also inherited as the autosomal recessive trait. The affected individual lacks an enzyme that converts the amino acid phenylalanine into tyrosine. As a result of this phenylalanine is accumulated and converted into phenylpyruvic acid and other derivatives. Accumulation of these in brain results in mental retardation. These are also excreted through urine because of its poor absorption by kidney. Answer:(d)
Q.14
ion Q67) In humans, curly hair is dominant (C) to straight hair (c). A woman who is heterozygote for curly hair marries to a normal man. What will be the probability of first and second child having curly hair?
0%
a) ¼
0%
b) ½
0%
c) 1/8
0%
d) 1/6
Explanation
Gametes
C
c
c
Cc (curly hair)
cc (straight hair)
c
Cc (curly hair)
cc (straight hair)
Woman with heterozygote Curly hair has genotype is Cc. straight hair man has genotype is cc. Cc × cc Probability of progeny having curly hair = ½. Answer:(a)
Q.15
ion Q68) Consider the following statements: (i) Every organisms has both autosomes and allosomes, the later determines sex. (ii) In man, males are heterogametic and females are homogametic. (iii) Females are heterogametic and males are homogametic in Drosophila. (iv) Males and females are heterogametic in birds. (v) Males are homogametic and females are heterogametic in hen. Of these statements:
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a) (iii) and (v) are correct.
0%
b) (i), (iii) and (iv) are wrong.
0%
c) (iii) and (iv) are wrong.
0%
d) (i) and (iv) are wrong.
Explanation
X and Y chromosomes are called sex chromosome also known as allosomes. Every organism has autosomes and allosomes. Birds has ZW-ZZ type in which male is homogametic (ZZ) and female is heterogametic (ZW) In human beings and in Drosophila the males have one X and one Y chromosome, whereas females have a pair of X-chromosomes besides autosomes Statement (i), (ii) and (v) is correct. Statement (iii) and (iv) Answer:(b)
Q.16
ion Q69) Due to non-disjunction of chromosomes during spermatogenesis, sperms carry both sex chromosomes (22A+XY) and some sperms do not carry any sex chromosome (22A+0). If these sperms fertilize normal eggs (22A+X), what types of genetic disorders appear among the offspring’s?
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a) Turner's syndrome and Klinefelter's syndrome.
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b) Down's syndrome and Klinefelter's syndrome.
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c) Down's syndrome and Turner's syndrome.
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d) Down's syndrome and cri-du-chat syndrome.
Explanation
Fertilization of sperms(22A+XY) with normal eggs (22A+X) will produce progeny with genetic disorder due presence of an additional copy of Xchromosome resulting into a karyotype of 47, XXY. This disorder is called Klinefelter’s Syndrome. Fertilization of sperm (22A+0) with normal egg (22A+X) will produce progeny with genetic disorder caused due to the absence of one of the X chromosomes, i.e., 45 with X0. This disorder is called Turner’s Syndrome. Answer:(a)
Q.17
ion Q70) Incomplete dominance was reported first in 4’o clock plant (Mirabilis jalapa) by:
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a) Mendel.
0%
b) Morgan.
0%
c) Bateson.
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d) Correns.
Explanation
Incomplete dominance is a phenomenon where there is no dominant-recessive relationship and thus intermediate trait is expressed in F1 generation. It was reported in Mirabilis jalapa by Correns. Answer:(d)
Q.18
ion Q71) Allele is the ... ...
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a) Alternate trait of gene pair
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b) Total number of genes for a trait
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c) Total number of chromosomes
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d) Total number of chromosomes of a haploid set.
Explanation
A pair of contrasting characters is called allele. Answer:(a)
Q.19
ion Q72) When there is no Possibility of independent assortment of genes during gametogenesis then What Will be the real ratio of F2 in dihybrd cross?
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a) 9 : 3 : 3 : 1
0%
b) 11 : 1 : 1 : 3
0%
c) 12 : 1 : 1 : 2
0%
d) 9 : 3 : 2 : 2
Explanation
Answer:(b)
Q.20
ion Q73) The cross between heterozygous A blood group mother with B blood group father heterozygous).What will be the expected blood group of First filial generation.
0%
a) AB group
0%
b) A group
0%
c) B group
0%
d) O group
Explanation
Gametes
I
A
I
O
I
B
I
A
I
B
(Blood group AB)
I
B
I
O
(blood group B)
I
O
I
A
I
O
(blood group A)
I
O
I
O
(blood group O)
Heterozygous blood group A (IAIO) and heterozygous blood group B (IBIO) when crossed has following expected blood group. AIO × IBIO Answer:(e)
Q.21
ion Q74) Assertion (A) :- pedigree is same in colourblindness and haemophilia Reason (R) :- Colourblindness and haemophilia are X -linked recessive traits.
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a) If both (A) and (R) are true and (R) is the correct explanation of (A)
0%
b) If both (A) and (R) are true but (R) is not the correct explanation of (A)
0%
c) If (A) is true but (R) is false
0%
d) If both (A) and (R) are false.
Explanation
Analysis of traits in a several of generations of a family is called the pedigree analysis. Colour Blidness and haemophilia are both sex linked recessive disease, i.e., mutation occurs on X chromosomes. Thus pedigree will be similar. Answer:(a)
Q.22
ion Q75) In a plant, red fruit (R) is dominant over yellow fruit (r) and tallness (T) is dominant over shortness (t). If a plant with RRTt genotype is crossed with a plant that is rrtt.
0%
a) 25% will be tall with red fruit
0%
b) 50% will be tall with red fruit
0%
c) 75% will be tall with red fruit
0%
d) All the offspring will be tall with red fruit.
Explanation
Gametes
RT
Rt
rt
RrTt (tall, red fruit)
Rrtt (dwarf, red fruit)
In case of colour of fruit, red is dominant over yellow. Thus, cross between RR and rr will produce heterozygous Rr progeny expressing red color. In case of height, Tall is dominant over dwarf. Thus, cross between Tt and tt will produce 50% tall and 50% dwarf. Considering both the traits, we can conclude that 50% of progeny will be tall with red fruit and 50% of progeny will be dwarf with red fruit. RRTt × rrtt Answer:(b)
Q.23
ion Q76) Which one of the following conditions in human is correctly matched with its chromosomal abnormality / linkage ?
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a) Erythro blastosis foetalis - X - linked
0%
b) Down's syndrome - 44 autosomes +XXY
0%
c) Kline Felter's syndrome - 44 autosomes +XXY
0%
d) Colour blindness - Y - linked.
Explanation
Colour Blidness : It is a sex-linked recessive disorder due to defect in either red or green cone of eye resulting in failure to discriminate between red and green colour. This defect is due to mutation in certain genes present in the X chromosome. Down’s Syndrome : The cause of this genetic disorder is the presence of an additional copy of the chromosome number 21 (trisomy of 21). Klinefelter’s Syndrome : This genetic disorder is also caused due to the presence of an additional copy of Xchromosome resulting into a karyotype of 47, XXY. Erythroblastosis fetalis is hemolytic anemia in the fetus (or neonate, as erythroblastosis neonatorum) caused by transplacental transmission of maternal antibodies to fetal red blood cells. Answer:(c)
Q.24
ion Q77) A test cross is carried out to ......
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a) determine the genotype of a plant at F1
0%
b) Predict whether two traits are linked
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c) assess the number of alleles of a gene
0%
d) determine whether two species or varieties will breed successfully.
Explanation
Gametes
T
t
t
Tt (tall)
tt (dwarf)
t
Tt (tall)
Tt (dwarf)
A cross of F1 hybrid with either of the two parents is known as back cross. 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 Tt × tt Answer:(a)
Q.25
ion Q78) A colour blind girl is rare because she will be born only when
0%
a) Her mother and maternal grandfather were colour blind
0%
b) Her father and maternal grandfather were colour blind
0%
c) Her mother is colour blind and father has normal vision
0%
d) Parents have normal vision but grandparents were colour blind.
Explanation
A daughter will not normally be colour blind, unless her mother is a carrier and her father is colour blind. Mother will be carrier when her father i.e., girl's maternal grandfather is colourblind. Answer:(b)
Q.26
ion Q79) Lethal genes are those which
0%
a) cause the death of the organism in which they are present
0%
b) cause the death of the homozygous infant being formed
0%
c) cause the death of heterozygous infant being formed
0%
d) all of the above
Explanation
Lethal alleles (also referred to as lethal genes or lethals) are alleles that cause the death of the organism that carries them. They are usually a result of mutations in genes that are essential for growth or development. Lethal genes are those genes which cause the death of organisms but only when they are present in the homozygous state. Answer:(d)
Q.27
ion Q80) A person meets with an accident and great loss of blood has occurred. There is no time to analyse his blood group. It is safe to transfuse blood of
0%
a) AB, RH+
0%
b) AB, RH−
0%
c) O, RH−
0%
d) O, RH+
Explanation
Blood group is determined by antigen. An antigen is any substance that causes your immune system to produce antibodies against it. Blood group O does not have antigen A and antigen B. Thus they can carry both anitbodies Anti-A and Anti-B in their serum. Rh- does not carry Rh antigen and thus can carry antibodies. So, correct answer O and Rh-. Answer:(c)
Q.28
ion Q81) A tall true breeding garden pea plant is crossed with a dwarf true breeding garden pea plant. When the F1 plants were selfed the resulting genotypes were in the ratio of
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a) 1: 2: 1: Tall heterozygous: tall homozygous: Dwarf
0%
b) 3: 1: Tall: Dwarf
0%
c) 3: 1: Dwarf: Tall
0%
d) 1: 2: 1: Tall homozygous: Tall heterozygous: Dwarf
Explanation
Gametes
T
t
T
RrTt (tall, red fruit)
Rrtt (dwarf, red fruit)
t
Tt (heterozygous tall )
tt (dwarf)
Pure line tall plant (TT) when crossed with pure dwarf plant (tt) produces heterozygous tall plant (Tt). F1 generation when selfed produces F2 generation. Tt × Tt TT : Tt : tt = 1 : 2 : 1 Answer:(d)
Q.29
ion Q82) Which one of the following conditions correctly describes the manner of determining the sex in the given example?
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a) XO type of sex chromosomes determine male sex in grasshopper
0%
b) XO condition in humans as found in Turner syndrome, determines female sex
0%
c) Homozygous sex chromosomes (XX) produce male in Drosophila
0%
d) Homozygous sex chromosomes (ZZ) determine female sex in birds
Explanation
Grasshopper is an example of XO type of sex determination in which the males have only one X-chromosome besides the autosomes, whereas females have a pair of X-chromosomes. Answer:(a)
Q.30
ion Q83) Phenotype of an organism is the result of:
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a) mutations and linkages
0%
b) Cytoplasmic effects and nutrition
0%
c) environmental changes and sexual dimorphism
0%
d) genotype and environmental interactions.
Explanation
Phenotype is the external feature of organism. It is the set of observable characteristics of an individual resulting from the interaction of its genotype with the environment. Answer:(d)
Q.31
ion Q84) If a homozygous red flowered plant is crossed with a homozygous white flowered plant, the offspring would be
0%
a) half red-flowered
0%
b) all red-flowered
0%
c) half white-flowered
0%
d) half pink- flowered.
Explanation
Red flower is dominant over white flower. F1 generation will express dominant trait. The offspring would be all red flower. Answer:(b)
Q.32
ion Q85) A child is born with an extra chromosome in each of its cells. This is usually the result of
0%
a) non disjunction
0%
b) crossing over
0%
c) segregation
0%
d) hybridization
Explanation
Failure of segregation of chromatids during cell division cycle results in the gain or loss of a chromosome(s), called aneuploidy. For example, Down’s syndrome results in the gain of extra copy of chromosome 21. Answer:(c)
Q.33
ion Q86) Which of the following conditions represents a case of co-dominance genes?
0%
a) A gene expresses itself, suppressing the phenotypic effect of its alleles.
0%
b) Genes that are similar in phenotypic effect when present separately, but when together interact to produce a different trait.
0%
c) Alleles, both of which interact to produce a trait, which may or may not resemble either of the parental types.
0%
d) Alleles, each of which produces an independent effect in a heterozygous condition.
Explanation
Co-dominance is the phenomenon where there is no dominant-recessive relationship and trait of both the allele is expressed. In heterozygous condition, each of alleles produces an independent effect in a heterozygous condition. Answer:(d)
Q.34
ion Q87) Which of the following statements are correct with respect to Law of dominance? i. Tall and dwarf traits were identical to their parental type and didn’t show any blending ii. Only one of the parental traits was expressed in F1 generation. iii. Both traits were expressed in the F2 generation. iv. The contrasting trait showed blending at F2 generation.
0%
a) ii, iii and iv
0%
b) i, ii and iii
0%
c) ii and iii
0%
d) i, ii, iii and iv
Explanation
The law of dominance is used to explain the expression of only one of the parental characters in a monohybrid cross in the F1 and the expression of both in the F2 . It also explains the proportion of 3:1 obtained at the F2 . There is no blending. Answer:(b)
Q.35
ion Q88) Study the pedigree chart given below: What does it show?
0%
a) Inheritance of a condition like Phenylketonuria as an autosomal recessive trait
0%
b) The pedigree chart is wrong as this is not possible
0%
c) Inheritance of a recessive sex-linked disease like haemophilia
0%
d) Inheritance of a sex-linked inborn error of metabolism like Phenylketonuria.
Explanation
1st generation is unaffected.Progenies both son and daughter is affected, this shows disorder is autosomal in nature. Third generation has affected male i.e.1/3 progeny when parents are unaffected. This shows it recessive in nature. Thus, the disorder is autosomal recessive like sickle cell anaemia or phenylketonuria. Answer:(a)
Q.36
ion Q89) Karyotype of the individual having Klinefelter’s syndrome shows:
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a) An extra copy of 21st chromosome.
0%
b) An extra copy of Y chromosome.
0%
c) An extra copy of X chromosome.
0%
d) Absence of Y chromosome.
Explanation
Klinefelter’s Syndrome : This genetic disorder is also caused due to the presence of an additional copy of Xchromosome resulting into a karyotype of 47, XXY. Such an individual has overall masculine development, however, the feminine development (development of breast, i.e., Gynaecomastia) is also expressed. Such individuals are sterile. Answer:(c)
Q.37
ion Q90) Gynaecomastia refers to
0%
a) Masculine development in females
0%
b) Development of breasts in males
0%
c) Development of female characters in male
0%
d) Reduced breasts in the female
Explanation
Gynecomastia (also spelled gynaecomastia) is the abnormal non-cancerous enlargement of one or both breasts in males due to the growth of breast tissue as a result of a hormone imbalance between estrogen and androgen. Answer:(b)
Q.38
ion Q91) The behavior of chromosomes and genes can be compared with each other is best explained by which of the following statement?
0%
a) occur in nucleus
0%
b) both segregate at the time of gamete formation leading to transmittance of complete pair to a gamete.
0%
c) Independent pairs (gene) or pair of chromosomes segregate independently of each other or of other pair.
0%
d) The two alleles of a gene pair are located on homologous site on homologous chromosomes.
Explanation
Two allelic genes are located on two homologous chromosomes. Experimental Verification of the Chromosomal Theory of Inheritance was done by Thomas Hunt Morgan and his colleagues. Morgan carried out various dihybrid crosses in Drosophila, with the genes that were sex-linked, i.e., the genes are present on the X-chromosome. . Morgan decided to use fruit flies to study how physical traits (for example, eye color) were transmitted from parents to offspring, and he was able to elegantly show that genes are stored in chromosomes and form the basis of heredity. . Answer:(c)
Q.39
ion Q92) You are studying the genetics of bean pigmentation in a particular variety of bean plant. A bean plant that produces grey beans is self-pollinated and the numbers of each progeny type produced are - 50 white beans 107 grey beans 38 black beans. Assuming that TWO genes govern the bean pigmentation trait, the genetic hypothesis that best explains the inheritance pattern of bean pigmentation would be:
0%
a) dominant/recessive
0%
b) incomplete dominance
0%
c) Incomplete penetrance
0%
d) recessive epistasis
Explanation
The ratio of white : grey : black = 1 : 2 : 1. This ratio suggests that there is no dominant-recessive relationship and intermediate trait hybrid. This phenomenon is called incomplete dominance. Answer:(d)
Q.40
ion Q93) In the given pedigree chart select the correct statement:
0%
a) A & B are twins
0%
b) A is younger than B
0%
c) B is younger than A
0%
d) Can’t determine the age of A & B
Explanation
Siblings are drawn from oldest to youngest with the oldest listed on the left and the youngest on the right. In this diagram, B is younger and A is elder. Answer:(c)
Q.41
ion Q94) The distance between gene A, B, C and D on a chromosome is as follows: A and C - 18 units A and B - 26 units A and D - 40 units B and C - 8 units B and D – 14 units The sequence of these genes would be-
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a) ABCD
0%
b) ACBD
0%
c) ADCB
0%
d) ACDB
Explanation
Distance between A and D is longest. Thus both will be at the terminal end. Distance between B and D is smaller compared to A and B. So, B will be closer to D and this makes as ACBD. Answer:(b)
Q.42
ion Q95) Select the correct statement from the ones given below with respect to dihybrid cross:
0%
a) Tightly linked genes on the same chromosomes show higher recombination.
0%
b) Tightly linked genes on the same chromosome show very few recombinations.
0%
c) Genes far apart on the same chromosome show very few recombination.
0%
d) Genes loosely linked on the same chromosome show similar recombination as the tightly linked genes.
Explanation
Morgan and his group also found that even when genes were grouped on the same chromosome, some genes were very tightly linked (showed very low recombination) while others were loosely linked (showed higher recombination). Answer:(b)
Q.43
on Q176) In two pea plants having red (dominant) coloured flowers with unknown genotypes are crossed, 75% of the flowers are red and 25% are white. The genotypic constitution of the parents having red coloured flowers will be
0%
a) both homozygous
0%
b) one homozygous and other heterozygous
0%
c) both heterozygous
0%
d) both Hemizygous
Explanation
The ratio of red flower : white flower is 3 : 1. This occurs when parents are heterozygous. Answer:(c)
Q.44
ion Q96) For a population of bacteria exposed to an antibiotic, most of them get killed but few survive and again increase their number. Choose the correct statement for the explanation of the experiment.
0%
a) Some of the bacteria tried and successfully adapted to the new conditions in the Petri dish.
0%
b) Some members of the bacteria population developed a resistance to the antibiotic immediately.
0%
c) Some members of the bacteria population already had a resistance to the antibiotic so they were not killed.
0%
d) Some of the bacteria quickly evolved into a new species that resists the antibiotic.
Explanation
Even after exposure to the antibiotic, a few bacteria are surviving, this is because, some members already had a resistance to the antibiotic and so these bacteria were not killed and survived which again reproduced, thereby increasing their numbers. Answer:(c)
Q.45
ion Q97) Consider the following: (i) The family pedigree of queen Victoria shows a number of haemophilic descendents. (ii) The genetic makeup of the sperm determines the sex of the child in humans. (iii) The number of chromosomes is always equal in male and female. (iv) Gene segregates at the time of gamete formation such that only one of each pair is transmitted to the gamete.
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a) Statements (i) and (ii) are wrong but (iii) and (iv) are correct.
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b) Statements (i), (ii) and (iv) are correct but (iii) is wrong.
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c) Statements (i), (ii) and (iii) are correct but (iv) is wrong.
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d) All statements are correct.
Explanation
Answer:(b)
Q.46
ion Q98) Pleiotropic gene:
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a) Controls only one phenotype.
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b) Controls several phenotypes.
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c) Masks the expression of another non – allelic genes.
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d) Inhibiting crossing over.
Explanation
The ability of a gene to have multiple phenotypic effect because it influences a number of characters simultaneously is known as pleiotropy. The gene having a multiple phenotypic effect because of its ability to control expression of a number of characters is called pleiotropic gene. Answer:(b)
Q.47
ion Q99) Assertion: Chromosomal map is constructed on the basis of determination of distance between genes on the basis of percentage of recombinants. Reason: Percentage of recombinants is directly proportional to the distance between genes on the chromosome.
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a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion.
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b) Both Assertion and Reason are true but Reason is NOT the correct explanation of Assertion.
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c) Assertion is true but Reason is false.
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d) Both Assertion and Reason are false.
Explanation
The process of determining the position of specific genes on specific chromosomes and constructing a diagram of each chromosome showing the relative positions of the genes.Assertion is true. Strength of the linkage between two genes is inversely proportional to the distance between the two, i.e., two linked genes show higher frequency of crossing over (recombination) if the distance between them is higher and lower frequency if the distance is small. Reason is correct explanation of assertion. Answer:(a)
Q.48
on Q100) Cross XXYy × xxYy yields Xx YY:XxYy :Xxyy:xxyy offspring in the ratio of
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a) 0 : 3 : 1 : 1
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b) 1 : 2 : 1 : 0
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c) 1 : 1 : 1 : 1
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d) 1 : 2 : 1 : 1
Explanation
Gametes
XY
Xy
xY
XxYY
XxYy
xy
XxYy
Xxyy
XXYy × xxYy Xx YY:XxYy :Xxyy:xxyy = 1 : 2 : 1 : 0 Answer:(b)
Q.49
on Q101) The first person to induce mutations was
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a) Hugo de Vries
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b) T.H. Morgan
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c) Sturtevant
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d) H.J. Muller
Explanation
Answer:(d)
Q.50
on Q102) Match each item in COLUMN I with one in COLUMN II and select your answer from the codes given:
SCIENTIST
CONTRIBUTION
A. Francis Crick
a. Breaking the genetic code
B. Nirenberg
b. Established Caenorhabditis elegans as a model genetics study organism
C. Benzer
c. Central dogma of molecular biology
D. Brenner
d. Bacteriophage genetics
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a) A =c B=a C= d D=b
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b) A =c d B=a C= b D=d
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c) A =a B=b C= c D=d
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d) A =a B=c C= d D=b
Explanation
Answer:(a)
0 h : 0 m : 1 s
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