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IB_BIOLOGYSYLLABUS2025_A.1.2
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IB_BIOLOGYSYLLABUS2025_A.2Genetic Similarity and DNA: Key Notes
Genetic Similarity
● Human-Chimp Similarity: Humans share 98.9% of their DNA with
chimpanzees. Despite this high genetic similarity, differences in the remaining
1.1% contribute to variations in appearance and behavior.
DNA: The Genetic Blueprint
● Definition: DNA (deoxyribonucleic acid) is a macromolecule that serves as
the genetic blueprint for all living organisms. It contains genes that determine
characteristics.
● Structure: DNA is a nucleic acid polymer made up of repeating units called
nucleotides.
Nucleic Acids
● Types: There are two main types of nucleic acids:
○ DNA: Contains genetic material in all living organisms.
○ RNA: Some viruses use RNA as their genetic material (e.g.,
SARS-CoV-2).
Nucleotide Components
● Components:
○ Pentose Sugar: Five-carbon sugar.
○ Nitrogenous Base: Contains nitrogen; examples include adenine (A),
guanine (G), cytosine (C), thymine (T) for DNA, and uracil (U) for RNA.
○ Phosphate Group: Phosphorus and oxygen.
Nucleotide Bonding
● Formation: Nucleotides link via covalent bonds between the phosphate group
of one nucleotide and the hydroxyl group of another, forming a
sugar-phosphate backbone.
● Directionality: Nucleotides are added in the 5′ to 3′ direction.
Nitrogenous Bases
● Types:
○ Purines: Adenine (A) and Guanine (G) with two rings.
○ Pyrimidines: Thymine (T), Cytosine (C), and Uracil (U) with one ring.
, ● Base Pairing: In DNA, A pairs with T and G pairs with C. In RNA, A pairs with
U.
Activities and Learning
● DNA Extraction: Conduct experiments to understand DNA isolation from
cells. Try the virtual lab for practical experience.
● Educational Activity: Create videos or labs to teach others about DNA
extraction and its significance.
These notes provide a foundational understanding of DNA, its structure, and its
importance in genetics.
Differences Between DNA and RNA: Key Notes
RNA World Hypothesis
● Theory: Suggests that early life forms may have used RNA, rather than DNA,
as their genetic material.
RNA vs. DNA: Structural Differences
1. Pentose Sugar
○ RNA: Contains ribose, a five-carbon sugar.
○ DNA: Contains deoxyribose, a five-carbon sugar with one less oxygen
atom than ribose.
2. Nitrogenous Bases
○ RNA: Has adenine (A), guanine (G), cytosine (C), and uracil (U)
(uracil replaces thymine).
○ DNA: Has adenine (A), guanine (G), cytosine (C), and thymine (T).
3. Strand Structure
○ RNA: Single-stranded molecule that forms a single continuous chain
of nucleotides.
○ DNA: Double-stranded molecule that forms a helical structure. The
two strands are antiparallel and linked by hydrogen bonds between
complementary bases (A pairs with T, G pairs with C).
4. Polymer Structure
○ RNA: Forms a single strand of nucleotides connected through
covalent bonds.
○ DNA: Forms a double helix structure with two strands connected by
hydrogen bonds.
Bonding and Formation
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