Module 3:
Genetics – DNA & Chromosomes
Objective
To understand the molecular basis of inheritance by studying the structure and
function of DNA, RNA, chromosomes, genes, and mutations, along with their
roles in replication, transcription, and genetic variation.
Table of Contents
1. Structure of DNA
o Nucleotides
o Double helix model
o Base pairing & Chargaff’s rules
o DNA conformations (A, B, Z forms)
2. DNA Replication
o Semi-conservative nature (Meselson–Stahl experiment)
o Steps: Initiation, Elongation, Termination
o Enzymes involved
o Leading & Lagging strands
3. Structure of RNA & Transcription
, o Types of RNA (mRNA, tRNA, rRNA)
o Transcription in prokaryotes & eukaryotes
o Post-transcriptional modifications
4. Chromosomes & Genes
o Nucleosome structure
o Euchromatin vs Heterochromatin
o Gene concept, locus & alleles
o Operons (prokaryotic gene organization)
5. Mutations
o Point mutations (silent, missense, nonsense)
o Frameshift mutations
o Causes: spontaneous & induced
o Effects on organisms
6. Exam-Orie
7. Exam oriented Practice Questions
o Multiple Choice Questions (MCQs)
o Short Answer Questions (SAQs)
o Long Answer Questions (LAQs)
8. Recommended Books
9. Cheat Note
, 1. Structure of DNA
DNA (Deoxyribonucleic acid) is the genetic material of almost all
living organisms. It was first identified by Friedrich Miescher in 1869
and its double helix structure was proposed by James Watson and
Francis Crick in 1953. The fundamental unit of DNA is the nucleotide,
consisting of a deoxyribose sugar, a phosphate group, and a
nitrogenous base. The bases are classified as purines (adenine and
guanine) and pyrimidines (cytosine and thymine). The DNA molecule
is a right-handed double helix with two antiparallel strands running in
opposite directions (5′→3′ and 3′→5′). The strands are held together
by hydrogen bonds between complementary bases (A pairs with T via
two hydrogen bonds, G pairs with C via three hydrogen bonds).
Chargaff’s rule states that the amount of adenine equals thymine, and
guanine equals cytosine in a DNA molecule. The double helix shows
major and minor grooves which are important for protein-DNA
interactions. DNA exists in different conformations: B-DNA (the most
common, right-handed helix), A-DNA (right-handed, more compact,
found in dehydrated conditions), and Z-DNA (left-handed, transiently
formed in GC-rich regions).
■ Exam Tip: Always mention Meselson–Stahl experiment while
describing replication.
Points to remember:
1. Structure of DNA
Definition: DNA (Deoxyribonucleic Acid) is the genetic material that
stores and transmits hereditary information.
Discovery:
Genetics – DNA & Chromosomes
Objective
To understand the molecular basis of inheritance by studying the structure and
function of DNA, RNA, chromosomes, genes, and mutations, along with their
roles in replication, transcription, and genetic variation.
Table of Contents
1. Structure of DNA
o Nucleotides
o Double helix model
o Base pairing & Chargaff’s rules
o DNA conformations (A, B, Z forms)
2. DNA Replication
o Semi-conservative nature (Meselson–Stahl experiment)
o Steps: Initiation, Elongation, Termination
o Enzymes involved
o Leading & Lagging strands
3. Structure of RNA & Transcription
, o Types of RNA (mRNA, tRNA, rRNA)
o Transcription in prokaryotes & eukaryotes
o Post-transcriptional modifications
4. Chromosomes & Genes
o Nucleosome structure
o Euchromatin vs Heterochromatin
o Gene concept, locus & alleles
o Operons (prokaryotic gene organization)
5. Mutations
o Point mutations (silent, missense, nonsense)
o Frameshift mutations
o Causes: spontaneous & induced
o Effects on organisms
6. Exam-Orie
7. Exam oriented Practice Questions
o Multiple Choice Questions (MCQs)
o Short Answer Questions (SAQs)
o Long Answer Questions (LAQs)
8. Recommended Books
9. Cheat Note
, 1. Structure of DNA
DNA (Deoxyribonucleic acid) is the genetic material of almost all
living organisms. It was first identified by Friedrich Miescher in 1869
and its double helix structure was proposed by James Watson and
Francis Crick in 1953. The fundamental unit of DNA is the nucleotide,
consisting of a deoxyribose sugar, a phosphate group, and a
nitrogenous base. The bases are classified as purines (adenine and
guanine) and pyrimidines (cytosine and thymine). The DNA molecule
is a right-handed double helix with two antiparallel strands running in
opposite directions (5′→3′ and 3′→5′). The strands are held together
by hydrogen bonds between complementary bases (A pairs with T via
two hydrogen bonds, G pairs with C via three hydrogen bonds).
Chargaff’s rule states that the amount of adenine equals thymine, and
guanine equals cytosine in a DNA molecule. The double helix shows
major and minor grooves which are important for protein-DNA
interactions. DNA exists in different conformations: B-DNA (the most
common, right-handed helix), A-DNA (right-handed, more compact,
found in dehydrated conditions), and Z-DNA (left-handed, transiently
formed in GC-rich regions).
■ Exam Tip: Always mention Meselson–Stahl experiment while
describing replication.
Points to remember:
1. Structure of DNA
Definition: DNA (Deoxyribonucleic Acid) is the genetic material that
stores and transmits hereditary information.
Discovery:
