10Mutation and Polypoidy

📚
INTRODUCTION
▢ Genetics:
❖ Topic: Mutation and Polyploidy
❖ Definition: Mutation is a sudden change in phenotype due to a change in the genome of a cell or virus.
❖ Discoverer:
◉ Name: Hugo de Vries
◉ Contributions:
  1. Discovered mutation in Oenothera lamarckiana (Evening primrose)
  2. Coined the term 'Mutation'
  3. Defined mutation as 'Sudden phenotypic changes which are heritable'
    4. ■ Note: Later discovered that mutation in Oenothera lamarckiana was due to polyploidy.
❖ Scientific Study: Given by Morgan
❖ Causes:
◉ Radiations:
◈ Gamma-rays: Produce free radicals
◈ X-rays: Cause deletion
◈ UV-rays: Cause dimer formation
◉ Mutation Effects:
  1. 99.9% mutations are harmful (lethal)
  2. Most common mutations: lethal, followed by recessive
Q1.
The most common type of mutation is
Q2.
Which of the following is correct about mutation?
❖ Stages of Occurrence:
  1. Before formation of gamete
  2. In gamete
  3. In zygote
❖ Importance:
  1. Useful in crop variety development
  2. UV-treated Penicillium strains yield high penicillin
  3. Phenotypic changes due to gene mutation are reversible; due to chromosomal changes are irreversible
  4. Allelic variations arise from mutation
  5. Ultimate cause of variation is mutation; major cause is sexual reproduction
  6. Basic cause of evolution
❖ Types:
  1. Natural
  2. Induced (via mutagens)
❖ Mutagens:
◉ Definition: Agents that cause mutations
◉ Types:
◈ Physical:
  1. Temperature
  2. Radiations
    3. ● Ionizing:
    1. X-rays
    2. γ-rays
    ● Non-ionizing:
    1. UV-rays
◈ Chemical:
  1. Mustard gas
  2. Acridine dye
  3. Colchicine
  4. Nitric oxide (NO)
  5. Maleic hydrazide
  6. Hydroxylamine
  7. Ethyl methane sulfonate (EMS)
◉ Notable Facts:
  1. H. J. Muller first induced mutation in Drosophila using X-rays
  2. H. J. Muller is called father of Actinobiology
  3. X-rays, β-rays used for deep-seated nucleus tissues; UV-rays for superficial ones
  4. First chemical mutagen made by C. Auerbach
❖ Mutation Rate: Natural mutation frequency is very low (1×10⁻⁵ to 1×10⁻⁶)
❖ Types of Mutation:
◉ Forward: Wild type changes to new type
◉ Reverse: Mutant type changes back to wild
❖ Study Material:
◉ Best: Haploids
◉ Model Organisms:
  1. Drosophila (2n = 8)
  2. Neurospora (haploid; called Drosophila of plant kingdom, pink mould)
  3. E. coli
  4. Bacteriophage
◉ Discoveries:
  1. Beadle and Tatum discovered 'One gene one enzyme hypothesis' in Neurospora (Nobel Prize 1958)
  2. Yanofsky: 'One gene one polypeptide' theory
📚
TYPES OF MUTATION
▢ Gene Mutation / Point Mutation:
❖ Frame Shift Mutation:
◉ Description: Occurs due to insertion or deletion at initial/internal position; affects all downstream codons.
◉ Effect: Most dangerous mutation type.
◉ Examples:
  1. Deletion
  2. Addition/Insertion
❖ Substitution Mutation:
◉ Transition: Purine↔Purine or Pyrimidine↔Pyrimidine
◉ Transversion: Purine↔Pyrimidine
◉ Example: Sickle cell anemia caused by transversion
▢ Chromosomal Mutation:
❖ Structural Changes:
◉ Deletion: Loss of chromosome part
◉ Inversion: Reinsertion in reverse order (180° twist)
◉ Duplication: Part joins homologous chromosome
◉ Translocation: Part joins non-homologous chromosome
❖ Numerical Changes:
◉ Aneuploidy:
◈ Definition: Change in individual chromosome number
◈ Types:
■ Hypoaneuploidy:
● Nullisomic (2n–2): Loss of chromosome pair (non-survivable)
● Double monosomic (2n–1–1): Loss of 2 dissimilar chromosomes
● Monosomic (2n–1): Loss of one chromosome; causes Turner's syndrome (44+XO)
Q1.
If 2n = 14, how many monosomics are possible?
■ Hyperaneuploidy:
● Trisomy (2n+1):
  1. Patau syndrome (Trisomy 13)
  2. Edward's syndrome (Trisomy 18)
  3. Down's syndrome (Trisomy 21)
● Sex Chromosomal Trisomies:
  1. Super female (XXX)
  2. Klinefelter's (XXY)
  3. Super male (XYY)
  4. Double trisomy (2n+1+1)
● Tetrasomy (2n+2): e.g., Super female (XXXX)
◉ Euploidy:
◈ Definition: Change in entire haploid set
◈ Types:
■ Homoploidy: n
■ Polyploidy:
● Autopolyploidy:
⟣ Definition: Multiple sets from same genome
⟣ Examples:
➢ Autotriploid (AAA):
  1. Banana
  2. Grapes
  3. Doob grass
➢ Autotetraploid (AAAA):
  1. Barseem
⟣ Note: Autotriploids are always sterile
● Allopolyploidy:
⟣ Definition: Sets from different species
⟣ Examples:
➢ Allotetraploid (AAA'A'): Raphano brassica
➢ Allohexaploid (AAA'A'A"A"): Triticum spelta (Wheat)
● Autoallopolyploidy: e.g., AAAAA'A' / AAABBB
◈ Special Notes:
  1. Triticale is the first man-made cereal crop
  2. Autopolyploids form multivalents during synapsis
  3. Allopolyploids form bivalents
Q1.
Sudden heritable change in genetic material that introduces variation is called
📅CEE MBBS 2025
Q2.
Absence of a chromosome from diploid organism:
📅CEE MBBS 2024B
Q3.
All of the following are aneuploidy except:
📅CEE MBBS 2024a
Q4.
Chemical causing chromosomal abnormality is called:
📅CEE MBBS 2024a
Q5.
Which syndrome is caused by an additional copy of chromosome 18?
📅CEE MBBS 2023
Q6.
Addition of one extra chromosome is called:
📅CEE MBBS 2023
Q7.
If the haploid chromosome number is 20, then monosomy and tetrasomy have respectively:
📅CEE MBBS 2021
Q8.
Down syndrome is due to:
📅CEE BDS 2023
Q9.
Sickle cell anemia is related with:
📅CEE BDS 2021
Q10.
Theory of mutation is given by: [MOE-2003]
📅MOE-2003
Q11.
Which is true about mutation? [MOE-2002]
📅MOE-2002
Q12.
Gene mutation takes place in: [MOE-2057]
📅MOE-2057
Q13.
Smallest unit of mutation is [BPKIHS 1996]
📅BPKIHS 1996
Q14.
The disease present only in female foetus is: [BPKIHS 1998]
📅BPKIHS 1998
Q15.
The most widely used method for prenatal detection of genetic disorders is: [BPKIHS 2001]
📅BPKIHS 2001
Q16.
Which is wrong? [BPKIHS 2002)
📅BPKIHS 2002)
Q17.
True about human karyotyping: [BPKIHS 2003]
📅BPKIHS 2003
Q18.
Which among the following is known as "jumping genes" ?
📅BPKIHS 2007
Q19.
Down's syndrome is an example of: [IE -2002]
📅IE -2002
Q20.
Down's syndrome is due to [IE - 2003]
📅IE - 2003
Q21.
Smallest segment of genetic material affected by mutation is: [IE - 2004]
📅IE - 2004
Q22.
The syndrome in humans in which an individual somatic cells contain the 3 sex chromosomes XXX is: [IE - 2007]
📅IE - 2007
Q23.
Kleinfelter's syndrome is:
Q24.
Down's syndrome in human beings is due to [IE -2005]
📅IE -2005
Q25.
In human syndrome in which there is XXY chromosome in body [BPKIHS - 2016]
📅BPKIHS - 2016
Q26.
Transposons are [BPKIHS- 2014]
📅BPKIHS- 2014
Q27.
2n + 1 chromosome are found in [BPKIHS - 2013]
📅BPKIHS - 2013
Q28.
XXY chromosome is [BPKIHS - 2012]
📅BPKIHS - 2012
Q29.
If the haploid condition in plant has 7 number of chromosomes in its octaploid will be [BPKIHS 2011]
📅BPKIHS 2011
Q30.
Webbed neck is found in syndrome? [BPKIHS - 2011]
📅BPKIHS - 2011
Q31.
The condition of gynaecomastism is due to genetic disorder called Klinfelter's syndrome in which the heterosome consists of: [BPKIHS - 2011]
📅BPKIHS - 2011
Q32.
Down's syndrome is [IOM-2016]
📅IOM-2016