CBSE 12th Standard Biology Subject Principles of Inheritance and Variation HOT Questions 3 Marks Questions 2021
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CBSE 12th Standard Biology Subject Principles of Inheritance and Variation HOT Questions 3 Marks Questions 2021
12th Standard CBSE
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Reg.No. :
Biology
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Identify the phenomenon in the following example-
"Sickle cell anaemia is an autosomal recessive trait.It is caused by the substitution of anino acid glutamic acid by valine at the sixth position of the beta globin chain of haemoglobin.This substitution of amino acid occurs due to phenomenon in which the sixth codon of beta globin gene is transformed from GAG to GUG". -
A man having blood group A is married with an woman having blood group B.work out the genotype of man and woman if their one of the children is born with blood group O.what is the possible genotype of other offsprings.
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Flowers of garden pea are biseual and self pollinated.therefore,it is difficult to perform hybrindization experiment by crossing a particular pistil with the specific pollen grains.Hoew mendel made it possible in his monohybrid, dihybrid and trihybrid crosses?
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Determine the genotype of offsprings in a cross between normal male and female cockroaches.
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How many linkage groups are present in the organism whose genomic chromosome number is n=8?
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A normal male marries a carrier female for haemophilia.What is the possibility of male child being haemophic and what is the probability of female carrier?what is the probability of female child infected?
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The genes A,B,C and D are located on the same chromosome in such a way that the distance between A nad B is 7 map units between B and C is 2 map units between C and D is 4.5 map units.What is the distance between A and D?what is the probability of linkage betweenB and D and between A and D?
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Explain with an example, where a gene, which carries a major disadvantage in homozygous condition.
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The traits are inherited through generations.This fact is based on the principles proposed by Gregor Mendel in 1865. However,Mendel dis not discovered these principles of inheritance by studying human beings then how his principles are applied in case of humans.
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Study the given pedigree chart and answer the questions that follow.
(a) Is the trait recessive or dominant?
(b) Is the trait sex-linked or autosomal?
(c) Give the genotypes of the parents shown in generation I and their third child shown in generation II and the first grandchild shown in generation III.
3 Marks
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CBSE 12th Standard Biology Subject Principles of Inheritance and Variation HOT Questions 3 Marks Questions 2021 Answer Keys
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The phenomenon is point mutation that involves substitution of a single nitrogenous base in DNA.
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If man is homozygous-IAIA and woman is also homozygous -IBIB then the offsprings will be -IAIB
If the man is hetrozygous-IAIi and the woman - IBIi then the offsprings will be
Thus the genotypes of parents are
Man=IAIi woman=IBIi
genotypes of offsprings are-IAIB , IAIi ,IBIi and IiIi -
It is true that flowers of garden pea are bisexual.However,Mendel made these flowers unisexual by artificial means.He emascualted bisexual flowers to make them female flowers.Collected pollen grains from those flowers which were regarded function male flowers.Thius the pollen grains of specific male flowers were dusted over the stigma of emasculated flower to complete the process of hybridization.Finally the seeeds were collected and sown to obtain F1 plants.
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In case of cockroaches the males have old sex chromosomes (AA + X)whereas the female have two homomorphic sex chromosomes(AA + XX) The male cockroach is heterogametic and produces two type of gemetes A+ X , A + O.The progeny is obtained in the ration of 50 male : 50 females.The genotype of offsprings 50% AA+XX and 50% AA+XO -
The number of linkage group in an organism corresponds to its haploid number of chromosomes.Therefore the number of linkage groups in the given organism is 8.
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male sex is determined by Y-chromosome which does not bear the gene for haemophilia.In the given case, when a normal male marries a carrier female the resultant offsprings will be follows- this marriage results in the four types of offsprings in equal ratio i.e .,
Normal Girl with XX genotype
Normal boy with XY genotype
carrier Girl with XXh genotype
The defect of haemophilia does not appear in the girl carrier because the second X chromosome possesses therefore female child can be a carrier but does not develop diseases.The male child on the other hand can develop the disese. -
The distance between A and D is 0.5 map units.The probability of linkage between B and D is poor whereas chances of linkage between A and D are maximum.
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An example for this condition is sickle-anaemia. The person with homozygous condition (Hbs Hbs ) for sickle-cell anaemia does not survive beyond the age of 20 years.
The individual with normal gene (HbHb) does not have sickle-cell anaemia but they are sensitive towards malaria.
The person with heterozygous condition (HbHbs) for sickle-cell anaemia does not develop both sickle-cell anaemia and malaria.
Due to abnormal haemoglobin, the malarial parasite will not harm the person.
Hence, in this case, the heterozygous condition has more survival chances, an advantage with respect to the homozygous individuals. -
Mendel performed his experiments on pea plants,i.e pisum sativum.After eight years of tedious experiments with pea plants, he proposed three fundamental principles of inheritance.These principles eventually assisted clinicians in human disease research,e.g after a few years of the discovery of Mendel's work,Archibald Garrod applied Mendel's principles to his study of alkaptonuria.Today, Mendalwhether we talk about pea plants or humans,genetic traits that follow the rules of inheritanceMendel proposed are called Mendelian Principles.
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(a) It is a dominant trait.
(b) It is autosomal.
(c) Genotypes of parents in generation I:
Female aa; male Aa.
Genotype of third child in generation II: Aa.
Genotype of first grandchild in generation III: Aa
3 Marks
