🧬 VCE Biology Unit 3 – AOS 1 Notes
What is the role of nucleic acids and proteins in maintaining life?
🔹 1. Nucleic acids as information molecules
🧪 DNA structure
DNA (deoxyribonucleic acid) stores genetic information.
Key features:
Double helix structure
Made of nucleotides, each containing:
o Phosphate group
o Deoxyribose sugar
o Nitrogenous base
Bases:
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
Base pairing:
A pairs with T
C pairs with G
→ held by hydrogen bonds
Important properties:
Antiparallel strands (run in opposite directions)
Sequence of bases = genetic code
🧬 RNA types
RNA is single-stranded and uses uracil (U) instead of thymine.
1. mRNA (messenger RNA)
Carries genetic code from DNA → ribosome
Contains codons (triplets of bases)
2. tRNA (transfer RNA)
, Brings specific amino acids to ribosome
Has anticodon (complementary to mRNA codon)
3. rRNA (ribosomal RNA)
Forms part of ribosome
Catalyses peptide bond formation
🔍 Comparison of DNA vs RNA nucleotides
Featur
DNA RNA
e
Sugar Deoxyribose Ribose
Strands Double Single
Bases A, T, C, G A, U, C, G
Functio Long-term Protein
n storage synthesis
🔹 2. The genetic code
🧾 Key properties:
Triplet code → 3 bases = 1 codon
Universal → same across almost all organisms
Degenerate → multiple codons code for same amino acid
Example:
UUU and UUC both code for phenylalanine
🔹 3. Gene expression
🧪 Step 1: Transcription (DNA → mRNA)
Occurs in nucleus (eukaryotes)
Process:
1. DNA unwinds
2. RNA polymerase binds to promoter
3. Complementary RNA nucleotides added
4. mRNA strand formed
What is the role of nucleic acids and proteins in maintaining life?
🔹 1. Nucleic acids as information molecules
🧪 DNA structure
DNA (deoxyribonucleic acid) stores genetic information.
Key features:
Double helix structure
Made of nucleotides, each containing:
o Phosphate group
o Deoxyribose sugar
o Nitrogenous base
Bases:
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
Base pairing:
A pairs with T
C pairs with G
→ held by hydrogen bonds
Important properties:
Antiparallel strands (run in opposite directions)
Sequence of bases = genetic code
🧬 RNA types
RNA is single-stranded and uses uracil (U) instead of thymine.
1. mRNA (messenger RNA)
Carries genetic code from DNA → ribosome
Contains codons (triplets of bases)
2. tRNA (transfer RNA)
, Brings specific amino acids to ribosome
Has anticodon (complementary to mRNA codon)
3. rRNA (ribosomal RNA)
Forms part of ribosome
Catalyses peptide bond formation
🔍 Comparison of DNA vs RNA nucleotides
Featur
DNA RNA
e
Sugar Deoxyribose Ribose
Strands Double Single
Bases A, T, C, G A, U, C, G
Functio Long-term Protein
n storage synthesis
🔹 2. The genetic code
🧾 Key properties:
Triplet code → 3 bases = 1 codon
Universal → same across almost all organisms
Degenerate → multiple codons code for same amino acid
Example:
UUU and UUC both code for phenylalanine
🔹 3. Gene expression
🧪 Step 1: Transcription (DNA → mRNA)
Occurs in nucleus (eukaryotes)
Process:
1. DNA unwinds
2. RNA polymerase binds to promoter
3. Complementary RNA nucleotides added
4. mRNA strand formed
