CHROMOSOMAL ORGANISATION (Chroma-color, soma-body)
- Discover by – Strasburg 1875/ Darlington/ Walther Flemming in 1882
- Name – Waldeyer 1888
- These are the genetic material which are present in nucleus
- It can be seen in Metaphase stage of cell division
- It made up of DNA and the genetic carrier gene are present on it
- These are capable of self replication.
- These are transmit genetic material from one generation to another generation by the genes, these are called genetic carrier
Chromosome Numbers
- All animals have a characteristic number of chromosomes in their body cells called the diploid (or 2n) number. This (2N) No. is fixed in all spp
- These occur as homologous pairs, one member of each pair having been acquired from the gamete of one of the two parents of the individual whose cells are being examined.
At the time of gametes formation, their number remains half (N), that becomes 2N again after fertilization.
- Eg- Onion (2N)=16 N= 8
- Human 2N = 46 N= 23
- Zea mays 2N= 20 N=10
- Tomato 2N=24 N=12
- Potato 2N= 78, Wheat 2N= 42 Cotton 2N= 52 Cabbage = 2N 18
Eukaryotic Chromosome Organization
The following material are present in the Eukaryotic Chromosome
- 1 DNA
- 2 RNA
- 3 Protein (A) Histone (B) Non Histone
- 4 Ca, Fe, Mg, Zn.
- The chemical composition is different in all the stages of cell division.
- E.g.- During the Metaphase stage DNA- 15-20% RNA 10-15% and Protein 68-72% otherwise during the Interphase – DNA Become increase 33-40%
1.DNA
- Chromosome are formed by the multiple coiling of DNA
- The DNA which is present in the chromosome controls all metabolic activity and genetic activity.
- In eukaryotic cell two types of DNA are present
- 1- Normal/Unique /Non Repetitive DNA
- 2- Repetitive DNA
- This is present in an alternative sequence.
- In eukaryotic cells 30-35 % DNA are unique DNA.
- In Unique DNA the bases are different from each other.
- This DNA formed Gene which is called Exon / Cistron.
- In Repetitive DNA Base sequences are repeated many times.
- It formed Heterochromatic part.
- These are called Intron
RNA
- 5% RNA is present in Chromosome
- It is called Chromosomal RNA
- It help in binding of Protein to the DNA
- It forms chromatin fiber.
Protein
Two types of proteins are present in chromosomes.
1- Histone protein
- It is basic protein which made up of Arginine and Lysine
- It is 80% part of the total protein
- It is present in ratio of DNA : Histone = 1:1
- It is H1, H2a, H2b, H3, and H4 types
- It is bind to the major groove of the DNA
- In this the positive end histone is bound to the negatively charged end of phosphate in DNA by electrostatic bond, it gives DNA flexibility and stability.
2- Non – Histone protein
- It is 20% part of the total protein
- It is helpful in gene regulation.
- It does Histone DNA binding with the help of RNA.
3- Ca-Mg-Zn
They made ionic bond
And help in gene regulation
Q1. Chromosomes are best visible during which stage of cell division?
A. Interphase
B. Metaphase ✅
C. Prophase
D. Anaphase
(PYQ: NEET 2020)
Q2. Chromosomes are composed mainly of:
A. Lipids and carbohydrates
B. DNA and proteins ✅
C. RNA and lipids
D. Fats and amino acids
Q3. Who coined the term “Chromosome”?
A. Darwin
B. Waldeyer ✅
C. Strasburger
D. Flemming
(PYQ: CUET 2023)
Q4. Which scientist first observed chromosomes?
A. Waldeyer
B. Darlington
C. Strasburger ✅
D. Watson
Q5. DNA in chromosomes control:
A. Blood formation
B. Genetic traits only
C. Metabolic and genetic activities ✅
D. Movement
Q6. Diploid number of chromosomes in humans is:
A. 23
B. 22
C. 46 ✅
D. 92
Q7. Gametes contain how many chromosomes in humans?
A. 46
B. 23 ✅
C. 92
D. 12
Q8. Which of the following is not a component of eukaryotic chromosome?
A. DNA
B. RNA
C. Lipids ✅
D. Proteins
Q9. What is the DNA:Histone protein ratio in a eukaryotic chromosome?
A. 2:1
B. 1:1 ✅
C. 1:2
D. 3:1
Q10. Histone proteins are rich in:
A. Glycine
B. Alanine
C. Arginine and Lysine ✅
D. Valine
Q11. Which of the following is not a histone type?
A. H1
B. H3
C. H5 ✅
D. H2B
Q12. The gene-coding region of DNA is called:
A. Intron
B. Exon ✅
C. Operon
D. Codon
Q13. Non-coding repetitive DNA sequences form:
A. Euchromatin
B. Histones
C. Heterochromatin ✅
D. Centromere
Q14. What percentage of RNA is present in a chromosome?
A. 10%
B. 5% ✅
C. 15%
D. 2%
Q15. Which element is involved in gene regulation via ionic bonds?
A. Potassium
B. Calcium ✅
C. Sodium
D. Chlorine
Q16. What is the total chromosome number in wheat?
A. 48
B. 42 ✅
C. 78
D. 36
Q17. Which base sequence structure is characteristic of introns?
A. Non-repetitive
B. Unique
C. Repetitive ✅
D. None
Q18. What percent of proteins are non-histone proteins in chromosomes?
A. 80%
B. 20% ✅
C. 50%
D. 10%
Q19. Chromosomal RNA helps in:
A. Mutation
B. DNA replication
C. Protein binding to DNA ✅
D. RNA synthesis
Q20. Eukaryotic DNA has how much unique DNA?
A. 10%
B. 50%
C. 30-35% ✅
D. 90%
Q21. Which stage shows highest DNA content in the chromosome?
A. Interphase ✅
B. Metaphase
C. Anaphase
D. Telophase
Q22. What is the % composition of protein during metaphase?
A. 50-55%
B. 15-20%
C. 68-72% ✅
D. 90-95%
Q23. Exon is the coding region of:
A. RNA
B. Protein
C. DNA ✅
D. Ribosome
Q24. Intron is made up of:
A. Unique DNA
B. Repetitive DNA ✅
C. Histone DNA
D. Satellite DNA
Q25. Which DNA sequence is repeated multiple times in chromosomes?
A. Exon
B. Unique
C. Repetitive ✅
D. None
Q26. Histone proteins are bound to DNA by which type of bond?
A. Covalent
B. Hydrogen
C. Electrostatic ✅
D. Ionic
Q27. RNA in chromosomes helps in:
A. Energy production
B. Transport
C. Chromatin fiber formation ✅
D. Mutation
Q28. DNA is coiled into chromosomes through:
A. Linear stretching
B. Multiple coiling ✅
C. Spiral packing
D. Looping only
Q29. Which scientist discovered the chromosomal material?
A. Walther Flemming ✅
B. Watson
C. Crick
D. Hershey
Q30. Cistron is also known as:
A. Intron
B. Operon
C. Exon ✅
D. Plasmid
Q31. Which is NOT a eukaryotic DNA type?
A. Repetitive
B. Unique
C. Circular ✅
D. Non-repetitive
Q32. DNA’s control over metabolism is due to:
A. mRNA only
B. Protein synthesis regulation ✅
C. DNA replication
D. Cytoplasmic organelles
Q33. DNA is negatively charged due to:
A. Sugar group
B. Phosphate group ✅
C. Nitrogen base
D. Hydrogen bond
Q34. Which of the following is a basic protein?
A. Albumin
B. Histone ✅
C. Hemoglobin
D. Insulin
Q35. In eukaryotic chromosomes, what % of unique DNA is found?
A. 50-55%
B. 30-35% ✅
C. 70-80%
D. 10-15%
Q36. What is the function of non-histone proteins?
A. Only packaging
B. Energy supply
C. Gene regulation ✅
D. Replication initiation
Q37. What metal ions help regulate genes in chromosomes?
A. Na and K
B. Ca, Mg, Zn ✅
C. Fe and Cu
D. Co and Mo
Q38. The part of chromosome rich in genes is:
A. Heterochromatin
B. Satellite DNA
C. Euchromatin ✅
D. Telomeric DNA
Q39. The chromosome structure is most condensed in:
A. G1 phase
B. S phase
C. Metaphase ✅
D. Cytokinesis
Q40. Which chromosomal component helps in gene expression control?
A. DNA only
B. RNA only
C. Non-histone proteins ✅
D. Water molecules
Q41. What is the chromosome number in maize (Zea mays)?
A. 16
B. 20 ✅
C. 24
D. 10
Q42. Which phase shows max RNA in chromosome?
A. Anaphase
B. Telophase
C. Interphase ✅
D. Prophase
Q43. DNA + Protein complex is called:
A. Nucleoplasm
B. Chromatin ✅
C. Ribosome
D. Cytosol
Q44. Which histone variant helps in DNA compaction at linker region?
A. H3
B. H4
C. H2A
D. H1 ✅
Q45. What stabilizes DNA-histone interaction?
A. ATP
B. RNA
C. Electrostatic bond ✅
D. Enzymes
Q46. What is the chromosome number in tomato?
A. 12
B. 20
C. 24 ✅
D. 36
Q47. How are non-histone proteins different from histone?
A. Acidic and regulatory ✅
B. Basic and structural
C. Water-soluble only
D. Not in nucleus
Q48. DNA is made flexible due to interaction with:
A. Water
B. Histone proteins ✅
C. Carbohydrates
D. Sugars
Q49. In humans, which of the following pair is homologous?
A. X and Y
B. 21 and 22
C. Chromosome 1 from each parent ✅
D. None
Q50. Which component forms major part of metaphase chromosome by weight?
A. DNA
B. RNA
C. Protein ✅
D. Lipid