Principles of Inheritance and Variation | Class 12 | One Word Answer Type Questions | Topic - wise

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Topic 1: MENDEL’S LAWS OF INHERITANCE

Q 1: Study of inheritance, heredity and variation of characters is called ………….

✅ Genetics

Q 2: Who is the Father of Genetics?

✅ Gregor Mendel

Q 3: Transmission of characters from parents to progeny is called ………….

✅ Inheritance

Q 4: Difference between parents and offspring is called

✅ Variation

Q 5: Mendel conducted some hybridization experiments on

✅ Garden peas (Pisum sativum)

Q 6: Removal of anthers of one plant to avoid self-pollination is called

✅ Emasculation

Q 7: Mendel selected …… pairs of true breeding pea varieties.

✅ 7

Q 8: Which of the following is a recessive trait?

Tall stem, Yellow pod, Round seed, Axial flower.

✅ Yellow pod

Q 9: A cross involving 2 plants differing in one character pair is called

✅ Monohybrid cross

Q 10: Monohybrid phenotypic ratio is

✅ 3:1

Q 11: Monohybrid genotypic ratio is

✅ 1:2:1

Q 12: Alternative forms of a gene are called .........

✅ Allele

Q 13: The condition in which chromosome pair carries similar alleles of a gene is called

✅ Homozygous

Q 14: The condition in which chromosome pair carries dissimilar alleles of a gene is called

✅ Heterozygous

Q 15: The character which is expressed in heterozygous condition is ……………

✅ Dominant character

Q 16: The character which is suppressed in heterozygous condition is …………….

✅ Recessive character

Q 17: Physical expression of a character is called

✅ Phenotype

Q 18: Genetic constitution of a character is called

✅ Genotype

Q 19: A graphical representation to calculate probability of all genotypes of offspring in a genetic cross is called

✅ Punnett square

Q 20: Mendel called the things inherited from parents to offspring as factors. Now it is known as ………

✅ Genes

Q 21: Crossing of an organism with dominant phenotype to a recessive individual is called ……….

✅ Testcross

Q 22: Monohybrid test cross ratio is .........

✅ 1:1

Q 23: Mendel conducted ……... to determine F2 genotype.

✅ Test cross

Q 24: Test cross is used to find out the …………… of a character.

✅ Unknown genotype

Q 25: A cross between two parents differing in 2 pairs of contrasting characters is called

✅ Dihybrid cross

Q 26: Genotype of heterozygous round yellow is written as

✅ RrYy

Q 27: On observing the F2 of dihybrid cross, Mendel found that yellow and green colour segregated in a ……… ratio.

✅ 3:1

Q 28: Dihybrid Phenotypic ratio is

✅ 9:3:3:1

Q 29: Dihybrid genotypic ratio is

✅ 1:2:1:2:4:2:1:2:1

Q 30: According to the First Law (Law of Dominance), characters are controlled by discrete units called …………

✅ Factors

Q 31: During gamete formation, the factors (alleles) of a character pair present in parents segregate from each other such that a gamete receives only one of the 2 factors. This law is called ...........

✅ Law of Segregation (Mendel’s Second Law)

Q 32: Which Mendel’s law is based on the results of dihybrid crosses?

✅ Law of Independent Assortment (Mendel’s Third Law)

Q 33: When two pairs of traits are combined in a hybrid, segregation of one pair of characters is independent of the other pair of characters. This law is known as ...........

✅ Law of Independent Assortment

Topic 2: OTHER PATTERNS OF INHERITANCE

Q 34: An inheritance in which heterozygous offspring shows intermediate character between two parental characteristics is called

✅ Incomplete Dominance

Q 35: In snapdragon (dog flower or Antirrhinum), cross between homozygous red & white produces pink flowered plant. This is an example for

✅ Incomplete Dominance

Q 36: In ……………, phenotypic & genotypic ratios are same.

✅ Incomplete Dominance

Q 37: In incomplete dominance, phenotypic and genotypic ratios are

✅ 1: 2: 1

Q 38: In heterozygotes, Modified allele will be generally ............

✅ Recessive

Q 39: ………………. Is the inheritance in which both alleles of a gene are expressed in a hybrid.

✅ Co-dominance

Q 40: A classic example of codominance in genetics is the ............

✅ ABO blood group system

Q 41: ABO blood groups are controlled by the gene ..........

✅ I

Q 42: Genotypes of A group is either IA IA or …………

✅ IA i

Q 43: Genotype of AB group is always

✅ IA IB

Q 44: ii is the genotype of ………………

✅ O group

Q 45: In ABO system, …………. shows codominance

✅ IA IB

Q 46: When IA and IB are present together, they both express their own types of sugar antigens on RBC. This is due to ........

✅ Co-dominance

Q 47: The presence of more than two alleles of a gene to govern same character is called

✅ Multiple allelism

Q 48: For the gene of ABO blood grouping, there are ……... types of alleles.

✅ 3

Q 49: The inheritance in which some traits are controlled by several genes (multiple genes) is called

✅ Polygenic inheritance

Q 50: Human skin colour, human height etc. are examples of ……………. Inheritance.

✅ Polygenic

Q 51: In a ………….. trait, the phenotype reflects contribution of each allele, i.e., the effect of each allele is additive.

✅ Polygenic

Q 52: In human, the genotype of darkest skin colour is AABBCC and that of lightest skin colour is

✅ aabbcc

Q 53: A phenomenon in which a single gene exhibits multiple phenotypic expression is called

✅ Pleiotropy

Q 54: In heterozygous condition, starch grain size of pea plant is intermediate sized. So it is an example for ……….

✅ Incomplete dominance

Q 55: Phenylketonuria causes mental retardation, reduction in hair & skin pigmentation. So it is an example for ………

✅ Pleiotropy

Topic 3: CHROMOSOMAL THEORY, LINKAGE, RECOMBINATION

Q 56: In 1900, de Vries, Correns and …………. independently rediscovered Mendel’s results.

✅ von Tschermak

Q 57: Chromosomal Theory of Inheritance (1902) was proposed by .............

✅ Walter Sutton & Theodore Boveri

Q 58: ……………. united chromosomal segregation with Mendelian principles and called it the chromosomal theory of inheritance.

✅ Sutton

Q 59: ………………. proved chromosomal theory of inheritance using fruit flies (Drosophila melanogaster).

✅ Thomas Hunt Morgan

Q 60: The physical association of genes on a chromosome is called

✅ Linkage

Q 61: The generation of non-parental gene combinations is called

✅ Recombination

Q 62: The terms linkage and recombination were coined by

✅ Morgan

Q 63: Morgan carried out several dihybrid crosses in ………. to study sex-linked genes.

Drosophila

Q 64: In Drosophila, genes of body colour, eye colour and wing size are located on the ………..

✅ X chromosome

Q 65: When two genes are situated on same chromosome, proportion of parental gene combinations will be much higher than the non-parental type. This is due to ……………….

✅ Linkage

Q 66: In Drosophila, genes of white eye & yellow body were very tightly linked and showed only ………. recombination.

✅ 1.3%

Q 67: In Drosophila, genes of white eye & miniature wing were loosely linked and showed ………… recombination.

✅ 37.2%

Q 68: …………. genes show low recombination.

✅ Tightly linked

Q 69: ………… used the recombination frequency between gene pairs for measuring the distance between genes and mapped their position on the chromosome.

✅ Alfred Sturtevant

Topic 4: SEX DETERMINATION

Q 70: The chromosomes that are involved in sex determination are called

✅ Sex chromosomes

Q 71: The chromosomes other than sex chromosomes are called

✅ Autosomes

Q 72: In 1891, ………….. studied spermatogenesis in some insects and observed that 50 % of sperm received a nuclear structure after spermatogenesis, and other 50 % sperm did not receive it.

✅ Henking

Q 73: Who discovered X chromosome?

✅ Henking

Q 74: Sex determination mechanism of insects such as grasshopper is …………….

✅ XX-XO mechanism

Q 75: In which sex determination system, the number of chromosomes in the male and female are not equal?

✅ XX-XO

Q 76: Sex determination mechanism of Human and Drosophila is …………….

✅ XX-XY mechanism

Q 77: The sex determination mechanism of birds is ..........

✅ ZZ-ZW

Q 78: In birds sex determination system, female is represented as ..........

✅ ZW

Q 79: In which sex determination mechanism, male shows homogamety and female shows heterogamety?

✅ ZZ-ZW mechanism

Q 80: During spermatogenesis, males produce 2 types of gametes: 50 % with X-chromosome and 50 % with …………

✅ Y-chromosome

Q 81: In XX-XY system, the ………. determines whether the offspring male or female.

✅ Sperm

Q 82: Sex determination in …………. is based on the number of sets of chromosomes an individual receives.

✅ Honeybee

Q 83: In honeybee, an unfertilised egg develops as a male (drone). It is called …………….

✅ Parthenogenesis

Q 84: In honeybee, females are diploid (32 chromosomes) and males are haploid (16 chromosomes). This is called as ………. sex determination system.

✅ Haplodiploid

Q 85: In Haplodiploid sex determination system, the males produce sperms by ……….

✅ Mitosis

Topic 5: MUTATION, PEDIGREE ANALYSIS AND GENETIC DISORDERS

Q 86: The alteration of DNA sequences resulting in changes in the genotype and phenotype of an organism is called

✅ Mutation

Q 87: The change (substitution) in a single base pair of a DNA is called ……………

✅ Point mutation

Q 88: …………….. is an example for point mutation.

✅ Sickle cell anaemia

Q 89: The deletion or insertion of base pairs resulting in the shifting of DNA sequences is known as

✅ Frame-shift mutation

Q 90: The agents which induce mutation are called

✅ Mutagens

Q 91: An analysis of genetic history of traits in several generations of a family is called

✅ Pedigree analysis

Q 92: The representation or chart showing family history is called

✅ Family tree (pedigree)

Q 93: In pedigree analysis, affected female is represented as

✅ ⬤

Q 94: The symbol 🔲 is used to represent ………….

✅ Male

Q 95: In pedigree analysis, the symbol used for sex unspecified is

✅ ◇

Q 96: What is the symbol used in pedigree that shows consanguineous mating?

✅ 🔲=◯

Q 97: The disorders caused by alteration or mutation in the single gene are called

✅ Mendelian Disorders

Q 98: Which of the following is not a Mendelian disorder?

Sickle-cell anaemia, Down’s syndrome, Thalassemia, Cystic fibrosis.

✅ Down’s syndrome

Q 99: The pattern of inheritance of Mendelian disorders can be traced in a family by …………

✅ Pedigree analysis

Q 100: An example for the disease caused due to Autosomal dominant allele is

✅ Myotonic dystrophy

Q 101: A sex linked (X-linked) recessive disease, in which a protein involved in the blood clotting is affected is called ……………..

✅ Haemophilia

Q 102: In females, haemophilia is very rare because it happens only when mother is at least ………. and father haemophilic.

✅ Carrier

Q 103: Queen Victoria was a carrier of …………….

✅ Hemophilia

Q 104: A sex-linked recessive disorder due to defect in either red or green cone of eye is called

✅ Colour blindness

Q 105: Colour blindness results in failure to discriminate between ..........

✅ Red and green colour

Q 106: Colour blindness results occurs in 8% of males and ………. of females.

✅ 0.4%

Q 107: The son of a woman heterozygous for colour blindness has a ………… chance of being colour blind.

✅ 50%

Q 108: Sickle cell anaemia occurs in both sexes as it is ………… recessive disease.

✅ Autosome-linked

Q 109: Sickle cell anaemia is controlled by a pair of alleles such as .........

✅ HbA & HbS

Q 110: The genotype of sickle cell anaemic person is

✅ HbSHbS

Q 111: Sickle cell anaemia is caused by the substitution of Glutamic acid by ……… at the sixth position of the β-globin chain of the haemoglobin (Hb).

✅ Valine

Q 112: Sickle cell anaemia is due to the single base substitution at the sixth codon of the β-globin gene from GAG to …………

✅ GUG

Q 113: In Sickle cell anaemia, shape of the ……… changes from biconcave disc to elongated sickle like structure under low oxygen tension.

✅ RBC

Q 114: …………… is an autosomal recessive disease resulting from an inborn error of metabolism.

✅ Phenylketonuria

Q 115: Phenylketonuria is due to mutation of a gene that codes for the enzyme ……………… responsible for the conversion of an amino acid phenylalanine into tyrosine.

Phenylalanine hydroxylase

Q 116: In a patient with Phenylketonuria, phenylalanine accumulates and converts into …………… and other derivatives.

✅ Phenyl pyruvic acid

Q 117: An autosome-linked recessive blood disease that results in reduced synthesis of α or β globin chains of haemoglobin is called ………….

✅ Thalassemia

Q 118: In α Thalassemia, production of α globin chain is affected due to the mutation or deletion of two closely linked genes …………. on chromosome 16.

✅ HBA1 & HBA2

Q 119: In β Thalassemia, production of β globin chain is affected due to the mutation of a single gene HBB on ………….

✅ Chromosome 11

Q 120: Thalassemia is a quantitative problem of haemoglobin whereas …………. is a qualitative problem.

✅ Sickle-cell anaemia

Q 121: The gain or loss of chromosomes due to failure of segregation of chromatids during cell division is known as .........

✅ Aneuploidy

Q 122: An increase in a whole set of chromosomes due to failure of cytokinesis after telophase stage of cell division is known as

✅ Polyploidy (Euploidy)

Q 123: Which of the following is not a chromosomal disorder?

Myotonic dystrophy, Down’s syndrome, Turner’s syndrome, Klinefelter’s Syndrome.

✅ Myotonic dystrophy

Q 124: The presence of an additional copy of chromosome number 21 (trisomy of 21) is called

✅ Down’s syndrome

Q 125: Down’s syndrome was first described by ……….

✅ Langdon Down

Q 126: Karyotype of Down’s syndrome is ........

✅ 45 A + XX or 45 A + XY

Q 127: A child with short stature, small round head, broad flat face, furrowed big tongue and partially open mouth may have ..........

✅ Down’s syndrome

Q 128: The presence of an additional copy of X-chromosome in male (trisomy) is called

✅ Klinefelter’s Syndrome

Q 129: Karyotype of Klinefelter’s Syndrome is

✅ 44 A + XXY

Q 130: Feminine development such as Gynaecomastia, tall stature and sterility are the features of

✅ Klinefelter’s Syndrome

Q 131: The absence of one X chromosome in female (monosomy) is known as

✅ Turner’s syndrome

Q 132: Karyotype of Turner’s syndrome is ........

✅ 44 A + XO

Q 133: Sterility, rudiment ovaries, short stature and lack of other secondary sexual characters are the features of .........

✅ Turner’s syndrome

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