Namrata Das Exams Prep Master
Exams Prep Master
The chromosomal theory of inheritance was given by Sutton and Boveri in 1902 and 1903 individually. It is the fundamental theory of genetics, which states that ‘genes are the units of heredity found on the chromosomes’ Sutton and Boveri observed the behaviour of chromosomes, inside the nucleus during cell division. This theory proved the Mendelian law, by the segregation of the chromosomes during the Anaphase of cell division. Thomas Hunt Morgan used Drosophila melanogaster, a common fruit fly to show how sexual reproduction gave rise to variations.
In this article, based on the complexity, importance, and weightage of the respective chapters MCQs are carefully selected. Students can secure more marks in their exams if they practice these MCQs. Moreover, practicing such questions will be one of the best methods to ensure that they grasp all the important concepts in the syllabus.
Ques: The chromosomal theory of inheritance was proposed by-
- Mendel
- Watson and Crick
- Darwin
- Sutton and Boveri
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Ans: d
Explanation: Chromosomal Theory of Inheritance was proposed by Suttan and Boveri independently in years 1902 and 1903.
Ques: The mapping of genes on chromosomes was attempted by –
- Morgan
- W Sutton
- Henking
- Alfred Sturtevant
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Ans: a
Explanation: Gene mapping on chromosomes was done by Thomas Hunt Morgan on Drosophila melanogaster fly in 1913
Ques: Initial studies for sex determination were done on –
- Humans
- Hens
- Insects
- Plants
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Ans: c
Explanation: Drosophila melanogaster or Common Fruitfly was first used for sex determination studies by Morgan.
Ques: Which of the following doesn’t agree with the chromosomal theory of inheritance?
- The genes are located on chromosome
- The genes on the same chromosome are always passed together
- The genes are located linearly on the chromosomes
- The distance between two genes can be mapped
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Ans: b
Explanation: Genes from the same chromosome can show independent assortment as well by recombination. However, very close genes tend to be linked and are passed on together.
Ques: Pick out a wrong statement:
- Haemophilia is a sex-linked recessive gene disease
- Down’s Syndrome is due to aneuploidy
- Phenylketonuria is an autosomal recessive gene disorder
- Sickle cell anemia is an X-linked recessive gene disorder
- a & d are correct
- b and d are correct
- a, c, and d are correct
- a, b, and c are correct
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Ans: iv
Explanation: Haemophilia A and hemophilia B are inherited in an X-linked recessive pattern. The genes associated with these conditions are located on the X chromosome, which is one of the two sex chromosomes.
- Aneuploidy refers to a condition when there is an abnormal number of chromosomes. Down syndrome, also known as trisomy 21, is a genetic disorder caused by the presence of all or part of the third copy of chromosome 21.
- PKU is an autosomal recessive disorder, caused by mutations in both alleles of the gene for phenylalanine hydroxylase (PAH), found on chromosome 12. In the body, phenylalanine hydroxylase converts the amino acid phenylalanine to tyrosine, another amino acid.
Ques: Polytene chromosomes were first observed by
- Balbiani
- Steven and Wilson
- Batanetzky
- Heitz and Bauer
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Ans: a
Explanation: Polytene chromosomes were discovered by Balbiani (1881) in larval salivary glands, Malpighian tubules, intestine, hypoderm and muscles of Drosophila and Chironomus as a cylindrical cord that repeatedly unraveled and filled the nucleus.
Ques: The terminal end of a chromosome is called
- Centromere
- Chromomere
- Telomere
- Metamere
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Ans: c
Explanation: A telomere is a region of repetitive nucleotide sequences at each end of a chromatid, which protects the end of the chromosome from deterioration or from fusion with neighboring chromosomes.
Ques: The puffs and rings are associated with the
- Endoplasmic reticulum
- Polytene chromosomes
- Golgi bodies
- Nucleus
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Ans: b
Explanation: Puffs and rings are associated with the Polytene chromosomes, which were discovered by Balbiani in the Larval salivary gland of Drosophila melanogaster and Chironomus plumosus.
Ques: The theory of recombination of the linked gene due to crossing over of chromosome during zygotene of meiosis was put forward by:
- T.H. Morgan
- Punnet
- Mendel
- Connes
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Ans: a
Explanation: In 1911, while studying the chromosome theory of heredity, biologist Thomas Hunt Morgan had a major breakthrough. Morgan occasionally noticed that linked genes undergo crossing over during the zygotene stage of meiosis
Ques: When two genes are situated very close to each other in a chromosome-
- The percentage of crossing over between them is very high
- Hardly any crossing over is detected
- No crossing over can take place between them
- Only double cross overs can take place between them
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Ans: b
Explanation: When the genes are situated very close to one another genetic linkage is established. The closer the physical location of two genes on the DNA, the less likely they are to be separated by a crossing-over event.
Ques: The males of grasshoppers and moths possess two sets of autosomes and
- X and Y chromosomes
- Only X chromosome
- Only Y chromosome
- Neither X nor Y chromosome
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Ans: b
Explanation: Sex determining mechanism in grasshopper and bug is XX female and XO male type.
Ques: Relative morphologies of chromosomes of an individual indicate his/her –
- Genotype
- Phenotype
- Pedigree chart
- Karyotype
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Ans: d
Explanation: karyotype is an individual's collection of chromosomes, which indicates the relative morphologies of chromosomes.
Ques: Chromosomes found in the salivary gland of Drosophila is -
- Polytene
- Lamp-brush
- Supernumerary
- B-chromosomes
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Ans: a
Explanation: Polytene chromosomes are a strongly amplified form of interphase chromosomes, found in salivary gland cells of Drosophila.
Ques: Lamp-brush chromosomes occur in -
- Cancer cells
- Lymph glands
- Oocytes
- Salivary glands
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Ans: c
Explanation: Chromosomes transform into the lamp-brush form during the diplotene stage of meiotic prophase I due to the active transcription of many genes, which are found in the oocytes.
Ques: Chromosomes were first observed by –
- Fleming
- Hoffmeister
- Waldeyer
- Strasburger
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Ans: b
Explanation: Hoffmeister observed the first chromosome in 1848 in the nuclei of the pollen
mother cells of Tradescantia.
Ques: Puffs or Balbiani rings in the salivary gland chromosome are the sites of -
- Protein synthesis
- DNA replication
- RNA synthesis
- DNA duplication
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Ans: c
Explanation: Puffs and Balbiani rings are sites of active RNA synthesis, therefore, polytene chromosomes and more specifically puffs and Balbiani rings are excellent tools to study the induction and process of transcription.
Ques: What is the number of linkage groups in Drosophila?
- Two
- Four
- Eight
- None of the above
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Ans: b
Explanation: A linkage group is a linearly arranged group of linked genes that are normally inherited together except for crossing over.
- The number of linkage groups present in an individual corresponds to the number of chromosomes in its one genome. Fruit-fly Drosophila melanogaster has four linkage groups (4 pairs of chromosomes).
Ques: The centromere is that part of the chromosome where -
- Nicking occurs
- Chromatids are attached
- Nucleoli are formed
- Crossing-over takes place
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Ans: b
Explanation: Centromere is the specialized DNA sequence of a chromosome that links a pair of sister chromatids. During mitosis, spindle fibers attach to the centromere via the kinetochore and helps to keep chromosomes properly aligned when cells divide.
Ques: Chromosomal Theory of Inheritance is a combination of –
- Chromosomal segregation with the mendelian principle
- Dihybrid cross with the motion of chromosome
- Law of dominance with the chromosomal appearance
- Classical genetics with modern biology
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Ans: a
Explanation: CTI is a combination of chromosomal segregation with mendelian principle because it possesses Mendelian factors or genes and it is the chromosomes that segregate and assort independently during transmission from one generation to the next.
Ques: The linkage map of the X-chromosome of fruit fly has 66 units with yellow body gene (y) at one end and bobbed hair (b) gene at the other end. The recombination frequency between these two genes (y and b) would be
- 66%
- 100%
- 55%
- 48 %
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Ans: a
Explanation: Recombination frequency is the measure of genetic linkage in a gene map, a centimorgan (cM) is a unit that describes a recombination frequency of 1%, in this way the genetic distance between two loci can be measured based on their recombination frequency.
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