Advanced Concepts
The JEE-Advanced / NEET-hard concepts that separate top rankers — each a titled nugget with a real-world story, the idea in plain words, and a memory trick. Works even when the internet doesn't.
1,600 advanced concepts
“Cancer is the cell cycle's brakes failing — checkpoints that no longer stop a damaged cell dividing.”
DNA content change. Use it when before division.
DNA doubles in S phase (2C -> 4C)
“Cancer is the cell cycle's brakes failing — checkpoints that no longer stop a damaged cell dividing.”
Recombination timing. Use it when meiosis I.
Crossing over occurs in pachytene of prophase I
“Cancer is the cell cycle's brakes failing — checkpoints that no longer stop a damaged cell dividing.”
Mitosis makes two identical diploid cells in one division (growth/repair); meiosis makes four genetically varied haploid cells in two divisions (gametes).
“Cancer is the cell cycle's brakes failing — checkpoints that no longer stop a damaged cell dividing.”
A chromosome is the whole structure; after replication it has two identical sister chromatids joined at the centromere.
“Cancer is the cell cycle's brakes failing — checkpoints that no longer stop a damaged cell dividing.”
G1 is growth before DNA replication; G2 is growth after replication, preparing the cell for division.
“Cancer is the cell cycle's brakes failing — checkpoints that no longer stop a damaged cell dividing.”
DNA replicates in the S phase of interphase; mitosis only separates already-copied chromosomes.
“A monk counting peas uncovered the hidden algebra of heredity.”
The law of segregation and the law of independent assortment explain how alleles pass to offspring.
Memory trick: linked genes do not assort independently.
“A monk counting peas uncovered the hidden algebra of heredity.”
A frequent error is applying independent assortment to linked genes. In reality, the law of segregation and the law of independent assortment explain how alleles pass to offspring.
Memory trick: linked genes do not assort independently.
“A monk counting peas uncovered the hidden algebra of heredity.”
Some heterozygotes show a blend (incomplete) or both traits together (codominance, as in AB blood).
Memory trick: AB blood = codominance; pink flower = incomplete.
“A monk counting peas uncovered the hidden algebra of heredity.”
A frequent error is assuming one allele always fully masks the other. In reality, some heterozygotes show a blend (incomplete) or both traits together (codominance, as in AB blood).
Memory trick: AB blood = codominance; pink flower = incomplete.
“A monk counting peas uncovered the hidden algebra of heredity.”
A gene can have more than two alleles in a population, as with ABO blood groups.
Memory trick: ABO has three alleles: I^A, I^B, i.
“A monk counting peas uncovered the hidden algebra of heredity.”
A frequent error is thinking a gene has only two possible alleles. In reality, a gene can have more than two alleles in a population, as with ABO blood groups.
Memory trick: ABO has three alleles: I^A, I^B, i.
“A monk counting peas uncovered the hidden algebra of heredity.”
Genes on the same chromosome tend to stay together; recombination frequency maps their distance.
Memory trick: closer genes recombine less often.
“A monk counting peas uncovered the hidden algebra of heredity.”
A frequent error is thinking all genes assort independently. In reality, genes on the same chromosome tend to stay together; recombination frequency maps their distance.
Memory trick: closer genes recombine less often.
“A monk counting peas uncovered the hidden algebra of heredity.”
X-linked recessive traits (colour blindness, haemophilia) appear more in males.
Memory trick: X-linked recessives hit males more.
“A monk counting peas uncovered the hidden algebra of heredity.”
A frequent error is expecting equal expression in both sexes. In reality, X-linked recessive traits (colour blindness, haemophilia) appear more in males.
Memory trick: X-linked recessives hit males more.
“A monk counting peas uncovered the hidden algebra of heredity.”
One gene can affect many traits (pleiotropy) and many genes can shape one trait (polygenic, like height).
Memory trick: height and skin colour are polygenic.
“A monk counting peas uncovered the hidden algebra of heredity.”
A frequent error is assuming one gene means one trait. In reality, one gene can affect many traits (pleiotropy) and many genes can shape one trait (polygenic, like height).
Memory trick: height and skin colour are polygenic.
“A monk counting peas uncovered the hidden algebra of heredity.”
Non-disjunction causes conditions like Down (trisomy 21), Turner (XO) and Klinefelter (XXY).
Memory trick: Down = extra 21; Turner = single X.
“A monk counting peas uncovered the hidden algebra of heredity.”
A frequent error is mixing up which chromosome number changes. In reality, non-disjunction causes conditions like Down (trisomy 21), Turner (XO) and Klinefelter (XXY).
Memory trick: Down = extra 21; Turner = single X.
“A monk counting peas uncovered the hidden algebra of heredity.”
Phenotype ratio in F2. Use it when complete dominance.
Monohybrid cross ratio = 3:1
“A monk counting peas uncovered the hidden algebra of heredity.”
F2 phenotype ratio. Use it when independent assortment.
Dihybrid cross ratio = 9:3:3:1
“A monk counting peas uncovered the hidden algebra of heredity.”
Cross with homozygous recessive. Use it when reveals genotype.
Test cross ratio = 1:1
“A monk counting peas uncovered the hidden algebra of heredity.”
Genetic mapping. Use it when linked genes.
Recombination frequency = 1% ~ 1 map unit