L1 Basic Genetics
🧠Concepts Introduced
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paracetamol - reduce body temperature & inflamation, does not kill bacteria
antibiotic - only kills / inhibits bacteria, doesn't reduce body temperature & inflamation
Genetics
study of heredity & variation in living organisms ​explains how traits are passed down
genes, genetic, variation & heredity
importance:
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provides insights into inherited diseases
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support personalised medicine (tailoring treatment to genetic profiles)
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important in agriculture & biotech for crop improvement
History of Genetics
Gregor Mendel ​- discovered basic inheritance laws ​- concepts of dominant & recessive traits ​
Central dogma of molecular biology
DNA -> RNA -> Protein ​DNA stores information, RNA transcribes it, proteins execute functions
DNA structure & function
double helix ​pairs AT GC ​stores genetic instructions for growth & development
Chromosomes & Genes
chromosomes: long DNA molecules wrapped around proteins (histones)
46 chromosomes (23 pairs)
genes: specific DNA sequs coding for proteins or functional RNAs
Mendelian Inheritance
Law of Segregation: ​each parent contributes one allele to offspring
Law of Independent Assortment: ​genes for different traits are inherited independently
Non-Mendelian Inheritance
Incomplete dominance: ​blended traits like pink flowers with red x white
Codominance: ​both traits expressed (AB blood group)
Polygenic traits: ​controlled by multiple genes like height, skin , colour
Genetics Variations & Mutations
mutations: changes in DNA sequence (point mutation, insertion, deletion) ​- can be harmful, beneficial, neutral ​- source of genetic diversity & evolution
Application of Genetics
genetic testing: inherited disorders
personalised medicine: optimise drug therapy
biotechnology: genetically modified crops (GM), gene editing (CRISPR)
Cell cycle
Introduction to cell cycle
functions: growth , tissue repair, reproduction
ensures equal distribution of genetic material
Phases of cell cycle
Interphase (G1, S, G2): cell grows, replicates DNA, prepares for division
Mitotic Phase (M): division of nucleus (mitosis) and cytoplasm (cytokinesis)
Interphase G1 phase: ​- Cell increases in size and synthesizes proteins. ​- Organelles duplicate. ​- Major checkpoint for cell cycle progression
Interphase S phase: ​- DNA replication occurs ​- each chromosome duplicates into two sister chromatids ​- Critical for accurate genetic transmission
Interphase G2 phase: ​- Final preparations for mitosis. ​- Checks DNA for errors ​- Ensures organelles and proteins needed for mitosis are present.
Mitosis
Metaphase: ​- Chromosomes align at the metaphase plate (cell equator). ​- Spindle fibers attach to centromeres ​- Ensures equal separation of chromatids
Anaphase: ​- Sister chromatids separate and move to opposite poles. ​- Each chromatid becomes a daughter chromosome. ​- Key step for accurate chromosome distribution.
Telophase & Cytokinesis: ​- Nuclear envelope reforms around chromosomes. ​- Chromosomes decondense. ​- Cytokinesis divides the cytoplasm, forming two daughter cells.
Cell Cycle Checkpoints
A cell cycle checkpoint is a molecular quality-control stop sign. Instead of rushing blindly through division, the cell pauses its progress, runs diagnostic checks, and asks: "Are conditions right? Is everything working properly?"
If the answer is yes, the cell gets the green light to move to the next phase. If the answer is no, the cell freezes the cycle to fix the problem—or triggers cell self-destruction (apoptosis) if the damage is too bad to repair.
G1 checkpoint: checks DNA before replication.
G2 checkpoint: checks DNA after replication.
M checkpoint: ensures chromosomes attached to spindle before separation.
Regulation of cell cycle
Cyclins & CDK proteins that regulate cell cycle progression.
Tumor suppressor genes (p53, Rb): prevent uncontrolled cell growth.
Disruption leads to cancer
Meiosis vs Mitosis
Mitosis: produces 2 identical diploid cells (growth/repair).
Meiosis: produces 4 unique haploid cells (gametes).
Meiosis increases genetic diversity.
Cell cycle & cancer
Cancer results from uncontrolled cell division.
Caused by mutations in oncogenes or tumor suppressor genes.
Understanding genetics + cell cycle is key for cancer therapies.
Integration of genetics & cell cycle
Genes regulate progression of the cell cycle.
DNA repair genes fix damage during checkpoints.
Defects lead to genetic instability and disease.
